Dissertations / Theses on the topic 'Trees Diseases and pests Victoria'

Colonization of Pine Christmas trees by Verticicladiella procera Kendr. causes Procera root disease. Little is presently known regarding the pattern and effects of fungal development within colonized trees. The present studies were undertaken to elucidate the developmental pattern of the fungus in colonized trees, to gather information on possible mechanisms and physiological effects of disease development, and to explore the relationship between V. procera and other, well documented bluestain fungi. The presence of cellulose was demonstrated in the cell walls of X. procera, indicating the probable genetic relatedness of this fungus with Ophiostoma (Ceratocystis) bluestain fungi. Inoculation studies revealed that the fungus could penetrate wounded sapwood, and that colonized seedlings had lower water potentials than uncolonized seedlings. In addition, it was found that the fungus could persist in resinous stem lesions for 22 months without foliar symptoms, and resinous stem lesions with the fungus were significantly longer and deeper than wound lesions. An intensive isolation study revealed that the initial point of colonization in a tree is apparently at the root collar, progressing acropetally in both directions. Analysis of radial growth from increment cores showed that colonized trees had grown more slowly for the preceding three years than uncolonized trees. The sapwood moisture content of these cores was also significantly reduced in the colonized trees, indicating that the stem was drying out as symptoms developed. Histological examination of colonized sapwood showed that U fungal colonization of tissues progressed along rays and resin ducts, in a fashion similar to that of bluestain fungi. Permeability measurements demonstrated that symptomatic sapwood, either resin-soaked or black-stained, had significantly reduced water movement relative to asymptomatic sapwood.
Ph. D.

Data for this study were collected by the US Forest Service and the Pennsylvania Bureau of Forestry on nearly 600 plots in central Pennsylvania. Tree and stand characteristics recorded between 1978 and 1985 include estimates of percent defoliation on individual trees. Logistic regression using maximum likelihood estimation was employed to model individual-tree mortality of 15 species in central Pennsylvania that had been defoliated by the gypsy moth. Defoliation was estimated to the nearest ten percent for individual trees. Other variables used for prediction included stand basal area and an individual-tree relative basal area index. Success ranged from no fit for three of the species to an R value (a derivation of Akaike's information criterion) of .613 for white oak. The inclusion of defoliation in the models had a varied effect. For four of the species percent defoliation was not significant. For hickory and white oak respectively, percent defoliation raised the R value by .305 and .290 percentage points. As many as five models for each species were developed: one or two models with no defoliation measure in the model and one each for one, two or three consecutive years of defoliation measures. A beta and gamma function were used to model individual· tree basal area growth for the same 15 species. The models were fit using nonlinear least squares. Variables used include the relative basal area index, stand basal area, site index and a defoliation index that incorporated three years of individual-tree, percent defoliation. The beta and gamma functions fit equally well with values of (1 - relative mean square error) ranging from .1967 to .6290. Results for both models are presented for each species. The defoliation index was a significant variable for five of the fifteen species: white, chestnut, red, and black oak and sassafras.
Master of Science

The effects of gypsy moth defoliation on acorn production (the seed source for oak regeneration), and the forest floor regeneration environment were investigated. Parameters measured included: acorn quantity, weight, development, and viability; litterfall; and forest floor depth and biomass. Nineteen plots in north-central Virginia and western Maryland on which trees suffered heavy, moderate, or no defoliation were monitored over a two-year period.

Master of Science

Tree-ring chronologies from ten mixed conifer stands in the Colorado Front Ranges and New Mexico Sangre de Cristo Mountains were used to reconstruct timing, duration, and radial growth impacts of past outbreaks of western spruce budworm, Choristoneura occidentalis Freeman. Graphical and statistical comparisons of tree-ring chronologies from host and non-host tree species, in conjunction with Forest Service records of outbreaks during the twentieth century, revealed that outbreaks were identifiable only in the host chronologies as sharply reduced growth periods. These comparisons also showed that host and non-host tree-ring chronologies were generally similar between outbreaks and that both were responding in a similar manner to climatic variation. A study of defoliation and insect population data that was available for the New Mexico stands demonstrated that host radial growth from 1978 to 1983 was highly correlated with budworm activity. The non-host chronologies from each stand were used to correct the host chronologies for climatic and other non-budworm environmental variations by a differencing procedure. The corrected chronologies were then used to estimate the dates and radial growth effects of past budworm outbreaks. Tree-ring characteristics of twentieth century documented outbreaks were used as criteria for inferring the occurrence of outbreaks in previous centuries. At least nine periods of increased budworm activity were identified in the region from 1700 to 1983. The mean duration of reduced growth periods caused by known and inferred budworm outbreaks was 12.6 years, and the mean interval between initial years of successive outbreaks was 34.9 years. The mean maximum radial growth loss was 50 percent of expected growth, and the mean periodic growth loss was 21.6 percent. There was an unusually long period of reduced budworm activity in the first few decades of the twentieth century, and since that time outbreaks have been markedly more synchronous between stands. Increased synchroneity of outbreaks in the latter half of the twentieth century suggests that areal extent of outbreaks has increased. This phenomenon may be due to changes in the age structure and species composition of forests following harvesting and fire suppression in the late nineteenth and early twentieth centuries.

Thesis (PhD)--Stellenbosch University, 2001.
ENGLISH ABSTRACT: Bacterial canker of stone fruit, caused by Pseudomonas syringae pv. syringae, is one of the most destructive crop diseases in South Africa. Chemical control has failed completely and effective long-term management strategies will have to rely on the breeding of resistant host trees. To assist in such breeding programmes, investigations into the molecular basis of the interaction between P. s. pv. syringae and stone fruit trees have been undertaken in collaboration with the ARC-Fruit, Wine and Vine Research Institute in Stellenbosch. The aim of this dissertation was to clone and identify genes that are involved in interaction between the bacterial canker pathogen and stone fruit trees. In the first part of the study, the harpin encoding gene of a local strain of the pathogen, P. s. pv. syringae NV, was amplified in a polymerase chain reaction (PCR) strategy with primers based on the hrpAZB sequences of the bean pathogen, P. s. pv. syringae 61. Sequencing of this hrpZpssNvgene revealed a high degree of homology (96%) between the harpin encoding genes and harpin proteins of the two strains. The hrpZpssNvgene was subsequently cloned into the pMAL-c2 expression vector and expressed in Escherichia co/i. This system was used for the production of purified, biologically active, recombinant HrpZpSSNV protein. In the second part of the study, differential display (DD) technology was used to identify genes that are induced in stone fruit trees in response to P. s. pv. syringae and/or its harpin elicitor. For this purpose, actively growing shoots of two Prunus sa/icina cultivars, the moderately resistant cv. 'Laetitia' and the highly susceptible cv. 'Songold' were treated with recombinant harpinpssNvprotein or live P. s. pv. syringae NV bacteria. An untreated control and wounding control was included in the experiment. Total RNA was isolated for comparative mRNA analysis 24 hours after treatment. DD profiles were generated with fifteen primer combinations. Eight candidate bands were re-amplified, cloned and sequenced. Reverse transcription PCR was employed to verify the expression patterns of the cloned bands in the original RNA sample set. Two bands, DDc and DD4 were shown to be differentially expressed between treatments and/or cultivars, while no differences in the expression levels of the remaining six bands (DDa, DDe, DD3, DD5, DD6 and DD7) were observed. BLAST similarity searches yielded significant matches for DDe, DD4 and DD7 with plant defense-related genes.
AFRIKAANSE OPSOMMING: Bakteriese kanker van steenvrugte, wat deur Pseudomonas syringae pv. syringae veroorsaak word, is een van die mees verwoestende siektes van landbougewasse in Suid-Afrika. Chemiese beheermaatreëls het geheel en al misluk en effektiewe langtermyn beheerstrategieë sal op die teling van weerstandbiedende gasheerbome moet staatmaak. Ondersoeke na die molekulêre basis van die interaksie tussen P. s. pv. syringae en steenvrugbome is in samewerking met die LNR-Vrugte-, Wyn- en Wingerdnavorsingsinstituut in Stellenbosch van stapel gestuur om tot sulke telingsprogramme by te dra. Die doelwit van hierdie proefskrif was om gene wat betrokke is in die interaksie tussen die bakteriese kanker patogeen en steenvrugbome te kloneer en te identifiseer. In die eerste gedeelte van die studie is die harpien-koderende geen van 'n plaaslike ras van die patogeen, P. s. pv. syringae NV, geamplifiseer in 'n polimerase kettingreaksie (PKR)-strategie met peilers wat op die hrpAZB-geenopeenvolgings van die boontjiepatogeen, P. s. pv. syringae 61, gebaseer is. Volgordebepaling van hierdie hrpZpssNv-geen het 'n hoë vlak van homologie (96%) tussen die harpien-koderende gene en harpien proteïene van die twee rasse getoon. Die hrpZpssNv-geen is vervolgens in die uitdrukkingsvektor pMAL-c2 gekloneer en uitgedruk in Escherichia coli. Hierdie sisteem is vir die produksie van suiwer, biologies-aktiewe, rekombinante HrpZpssNv-proteingebruik. In die tweede gedeelte van die studie is die differensiaalvertoon (DD) tegniek gebruik om gene te identifiseer wat deur P. s. pv. syringae en/of sy harpien elisitar in steenvrugbome geïnduseer word. Vir hierdie doel is aktief-groeiende lote van twee Prunus sa/icina kultivars, die matig weerstandbiedende kv. 'Laetitia' en die hoogs vatbare kv. 'Songold', met rekombinante harpienpssNvproteïen of lewende P. s. pv. syringae NV bakterieë behandel. 'n Onbehandelde- en verwondingskontrole is in die eksperiment ingesluit. Totale RNA is 24 uur na behandeling vir vergelykende mRNA-analise geïsoleer. DD-profiele is met vyftien peilerkombinasies gegenereer. Agt kandidaatbande is geheramplifiseer en gekloneer, waarna hul DNA-opeenvolgings bepaal is. Trutranskriptase-PKR is gebruik om die ekspressiepatrone van die gekloneerde bande in die oorspronklike RNA monsters na te gaan. Daar is vasgestel dat twee van die bande, DDc en DD4, differensieel tussen kultivars en/of behandelings uitgedruk is, terwyl geen verskille in die ekspressievlakke van die oorblywende ses bande (DDa, DOe, 003, DOS, 006 en DO7) waargeneem is nie. BLAST-soektogte het betekenisvolle ooreenkomste vir DDe, DD4 en DD7 met plant weerstandsgeassosieerde gene opgelewer.

Defoliating insect systems, defined for the purposes of this thesis as being composed of insects which defoliate forest trees and the species with which they interact, such as their host trees and their natural enemy complexes, exhibit a wide variety of population behaviors. Similarly, a number of theories and models have been proposed to explain these behaviors. These theories emphasize the importance of different ecological processes, often concentrate on the defoliator and overlook the importance of other components. Also, much of the current understanding of the dynamics of these systems has come from forest pest research and management programs, tailored towards specific pest problems and often very short term in nature. This thesis develops and begins to test a general approach for the local dynamics of defoliating insect systems. This framework outlines the system components that are necessary to predict the behavior of defoliating insect systems. It includes ways in which the equilibrium structure of defoliating insect systems, defined as the number of equilibria for each system component, the population levels at which the equilibria occur, and the processes creating the equilibria, might be found. The framework also includes methods of inducing the qualitative behavior of these sys- terns, defined as the periodicity of defoliator outbreaks, the length of outbreaks, and the dynamics of other important system components between, during, and in the decline of defoliator outbreaks. The study begins with a detailed literature review of historical theories of defoliating insect system behavior and of the documented behavior patterns of these systems. Major classes of behavior are identified, as well as the various ecological processes which have been invoked to explain these behaviors. An analysis and documentation of the equilibrium structure and behavior of three defoliating defoliating insect systems, the eastern blackheaded budworm, the eastern spruce budworm, and the jack pine sawfly, are then used to develop general rules about how equilibrium structure and behavior can be explained. This analysis, coupled with the literature review, is used to develop the framework. The framework is then tested against historical defoliator population data and general syntheses of defoliating insect system research to assess its utility and predictability. The major results of the thesis are as follows. First, it appears that the structure and behavior of a defoliating insect system can be explained with five dynamic variables: the abundances of the defoliator; the foliage; the forest; the parasitoid; and the disease; and the effects of weather acting on the defoliator. Second, there appear to be 4 classes of defoliating insect system behavior. Third, the behavior that a defoliating insect system will exhibit seems to be determined by the magnitude of weather effects on defoliator survival and recruitment, the parasitoid numerical response to changing defoliator densities, the disease numerical response to changing defoliator densities, and the vulnerability of the forest to defoliation. Fourth, there seem to be four equilibrium structures the defoliator can exhibit, and one each for the parasitoid, the foliage, the forest, and the disease. Finally, the framework suggests that defoliating insect system structure and behavior can be induced with a particular, well-defined set of information. The framework is successful when applied to particular defoliating insect systems for explaining their behavior, but less successful in explaining defoliator equilibrium structure for other systems. Opportunities for more thorough testing of the framework exist if the particular types of data outlined above are gathered for defoliating insect systems. This lack of data for testing the framework make it currently difficult to clearly define those systems in which the framework is useful and those systems in which it is not. Experiments to test the framework are described and suggestions for future types of applied research on defoliating insect systems are presented.
Science, Faculty of
Zoology, Department of
Graduate

A review of the current understanding of forest tent caterpillar (Malacosoma disstria Hbn.) population dynamics in Ontario suggests that two climatic factors, the temperature at the time of larval feeding and the minimum temperature through the winter, play important roles in determining outbreaks. Comparing the pattern of defoliation to similarly scaled temperature records over 41 years in Ontario shows no relationship between the year to year dynamics of outbreaks and either the temperature through the larval feeding period or the minimum overwintering temperature. A long-term analysis suggests that outbreaks are less severe in those regions with low overwintering temperatures and a patchy distribution of host. This latter finding, combined with an analysis of the synchrony and spread of defoliation, suggests that adult dispersal may play an important role in shaping the dynamics of outbreaks.
Science, Faculty of
Zoology, Department of
Graduate

Thesis (MSc)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: The Cape Floristic Region (CFR) of South Africa is well-recognised for exceptionally high plant species diversity and endemism. However, little attention has been bestowed on the pests and pathogens in this region, even though these may greatly influence plant distribution and evolution. In this study we identify various arthropods and fungi as pests and diseasecausing organisms of the ecologically and economically important CFR-endemic tree taxa of Virgilia. We isolated, identified and determined the pathogenicity of key fungal taxa from diseased Virgilia trees throughout the CFR. In addition we evaluated the role of possible pest arthropod taxa, including bark beetles, phoretic mites, larvae of a cerambycid beetle and larvae of the endemic Leto venus (ghost moth), in the death of Virgilia trees. Key fungal taxa were identified by comparisons of the internal transcribed spacer rDNA regions of the isolated taxa with those available on GenBank. Pathogenicity of the most commonly encountered fungal taxa was determined both in the field and under greenhouse conditions. Five different disease symptoms were observed on Virgilia trees throughout the CFR. At Table Mountain, Virgilia oroboides subsp. oroboides showed symptoms of: (1) several small cankers on stems, seemingly caused by a Fusarium acuminatum-like fungus, (2) a root rot disease caused by Armillaria mellea and (3) small bracket fungi on stems associated with Schizophyllum commune. Virgilia oroboides from the Harold Porter National Botanical Garden was diagnosed with a root disease consistently associated with an un-described Phomopsis species. Virgilia oroboides subsp. ferruginea and V. divaricata from Knysna and the Tsitsikamma area often showed symptoms of rapid wilting and death. The Virgilia stems were damaged by the tunnelling larvae of the ghost moth and those of an unidentified cerambycid beetle. Galleries and the surrounding wood tissues often housed the ophiostomatoid fungi Ceratocystis tsitsikammensis and Ophiostoma plurianulatum. These seem to originate from nitidulid beetles found feeding on gum exudate. Pathogenicity trials confirmed the virulence of the undescribed Phomopsis species, the F. acuminatum-like fungus, S. commune and C. tsitsikammensis to Virgilia. All four morpho-species of bark beetles found in this study, together with phoretic mites on two of the beetle morphospecies, were only collected from dead and dying Virgilia hosts and were classified as secondary pests. Both beetle taxa and mites commonly carried spores of various Geosmithia spp. These are not pathogenic to Virgilia trees, but may be an important food source for the bark beetles, as it dominated the fungal community in galleries. The phoretic mites were unable to feed on their Geosmithia associates, but have been observed to feed on dead bark beetle larvae within galleries. This suggests that the relationship of bark beetles, mites and their associated Geosmithia species in this system is complex and in need of further study. Our results show that natural populations of Virgilia play host to numerous destructive pathogens, some of which are non-native (e.g. A. mellea) and a cause for special concern. Additionally, the isolation of the undescribed Phomopsis species and A. mellea from botanical gardens, with A. mellea now spreading to natural areas, calls for stricter control over the movement of organic material from these areas.
AFRIKAANSE OPSOMMING: Die Kaapse Floristiese Streek (KFS) van Suid-Afrika is bekend vir buitengewoon hoë plantspesie-diversiteit en endemisme. Min aandag is egter tot dusver geskenk aan die peste en patogene in hierdie streek, al mag hulle plantverspreiding en evolusie dramaties beinvloed. In hierdie studie identifiseer ons verskeie geleedpotige diere en fungi as peste en organismes wat siektes veroorsaak in die ekologies en ekonomies belangrike, KFS-endemiese boom genus Virgilia. Ons het die sleutel fungi vanaf Virgilia oor die hele KFS geisoleer, geidentifiseer en hulle patogeniteit bepaal. Addisioneel het ons ook die rol van moontlike pes geleedpotiges, insluitende baskewers, cerambycid kewerlarwes en die endemiese Leto venus (spookmot) in die dood van Virgilia bome geevalueer. Sleutel fungi taksa is geidentifiseer deur die interne getranskribeerde spasieerder rDNS streke van die geisoleerde taksa met die wat op GenBank beskikbaar was te vergelyk. Patogenisiteit van die mees algemeen geisoleerde fungi taxa is beide in die veld en onder glashuis-toestande bepaal. Vyf verskillende siekte simptome is by Virgilia bome regdeur die KFS waargeneem. By Tafelberg het Virgilia oroboides subsp. oroboides simptome getoon van: (1) verskeie klein kankers op stamme, blykbaar veroorsaak deur ‘n Fusarium acuminatum-agtige fungus, (2) ‘n wortelvrot siekte veroorsaak deur Armillaria mellea en (3) klein rakswamme op stamme geassosieer met Schizophyllum commune. Virgilia oroboides in die Harold Porter Nationale Botaniese Tuin is gediagnoseer met ‘n wortelvrot siekte wat altyd met ‘n onbeskryfde Phomopsis spesie geassosieer is. Virgilia oroboides subsp. ferruginea and V. divaricata van Knysna en die Tsitsikamma area het dikwels simptome getoon van vinnige verwelking en dood. Die Virgilia stamme is deur die tonnelende larwes van die spookmot en dié van ‘n ongeidentifiseerde cerambycid kewer beskadig. Galerye en die omringende houtweefsel het dikwels die ophiostomatoid fungi Ceratocystis tsitsikammensis en Ophiostoma plurianulatum gehuisves. Dit lyk asof hierdie fungi van nitidulid kewers afkomstig is wat op die gomuitskeidings gevoed het. Patogeniteitsproewe het die kwaadaardigheid van die onbeskryfde Phomopsis spesie, die F. acuminatum-agtige fungus, S. commune en C. tsitsikammensis teenoor Virgilia bevestig. Al vier morfo-spesies baskewer wat in hierdie studie gevind is, sowel as die foretiese myte op twee van die kewer morfo-spesies, is slegs van dooie of sterwende Virgilia gashere versamel, en is as sekondêre peste geklassifiseer. Beide kewerspesies en myt taksa het algemeen spore van verskeie Geosmithia spesies (Geosmithia pallida, G. flava, G. microcorthyli, G. sp. 1 en G. sp. 2) gedra. Die Geosmithia spesies is nie patogenies teenoor Virgilia bome nie, maar mag ‘n belangrike voedselbron vir die baskewers wees, aangesien dit die fungus-gemeenskap in die galarye gedomineer het. Die foretiese myte was nie instaat om op Geosmithia-assosiate te voed nie, maar is waargeneem om op dooie baskewer larwes te voed binne die galerye. Dit stel voor dat die verhouding van die baskewers, myte en hulle geassosieerde Geosmithia spesies in die sisteem kompleks is, en verdere studie benodig. Ons resultate dui aan dat natuurlike populasies van Virgilia gashere is vir verskeie destruktiewe patogene, sommige waarvan nieinheems (bv. A. mellea) wat ‘n bron van groot kommer is. Verder noodsaak die isolasie van die Phomopsis spesie en A. mellea, wat beide wortelvrot siektes in botaniese tuine veroorsaak, strenger kontrole oor die verskuiwing van organiese materiaal uit hierdie areas, veral gegewe dat A. mellea reeds na natuurlike areas versprei het.
The Centre of Excellence In Tree Health Biotechnology for a bursary and funding the research conducted in this study

Thesis (MScAgric)--University of Stellenbosch, 2003.
ENGLISH ABSTRACT: Various aspects of the biology and ecology of woolly apple aphid, Eriosoma lanigerum, were investigated, including initial galling damage caused by E. lanigerum to the roots of apple trees, the possible relationship between E. lanigerum and Xiphinema and Pratylenchus nematodes and the effectiveness of Biostart 2000® and Furfural® as possible control agents of E. lanigerum in the orchard. Preliminary root damage by first instar E. lanigerum feeding was characterized by the mechanical injury of endodermis and parenchyma tissues. Damage by second, third and fourth instar E. lanigerum was similar, but the symptoms were more pronounced. Damage caused by adults included a pronounced swelling at infected areas of the root. Cell walls hardened until the root was radially strengthened with sclerenchyma tissue and nonconducting xylem vessels while the cuticle expanded greatly through the growth of corklike cambium tissue. There was no direct relationship between the population dynamics of E. lanigerum and those of Xiphinema and Pratylenchus nematodes. The occurrence of E. lanigerum appeared to be seasonal while P. penetrans and Xiphinema numbers fluctuated erratically. Undamaged root nitrogen levels seemed to correspond with the normal root growth cycle. Nitrogen levels from galled roots were significantly lower than those of undamaged roots, probably due to E. lanigerum feeding. Soils rich in fine sand and clay sustained higher populations of E. lanigerum and Xiphinema than sandy soils. The number of E. lanigerum found in soil samples correlated well with the damage index allocated to the samples. The numbers of Xiphinema found in soil samples also correlated well with the damage index allocated to the samples according to suspected Xiphinema damage symptoms. Both Biostart 2000® and Furfural® were effective as control agents of woolly apple aphid. Furfural'Ï, a chemical waste product of the sugarcane industry, was however not as effective as Biostart 2000®, a product that includes an activator and three bacterial species, Bacillus laterosporus, B. chitinosporus and B. licheniformis. The bacteria in the Biostart 2000® treated pots could replicate themselves under suitable conditions while Furfural® dilutes with each watering. Biostart 2000® is also easier to prepare than Furfural® since the components of Biostart 2000® readily mix to form a paste easily thinned by water, whereas Furfural® is an oily substance that does not easily disperse in water. Root damage was initiated soon after E. lanigerum started feeding, however there was no apparent relationship between E. lanigerum and the nematode species. The most promising, environmentally friendly control measure was Biostart 2000®.
AFRIKAANSE OPSOMMING: Verskeie aspekte van biologie en die ekologie van die appel bloedluis, Eriosoma lanigerum, was ondersoek insluitende aanvanklike galvorming veroorsaak deur E. lanigerum op wortels van appelbome, die moontlike verwantskap tussen E. lanigerum en Xiphinema en Pratylenchus nematodes en die effektiwiteit van Biostart 2000® en Furfural® as moontlike beheeragente van E. lanigerum in die boord. Aanvanklike wortelskade deur eerste ins tar E. lanigerum voeding was gekenmerk deur die meganiese beskadiging van endodermale en parenchiem weefsel. Skade veroorsaak deur tweede, derde en vierde instar E. lanigerum was soortgelyk alhoewel die simptome meer beklemtoond was. Skade deur volwassenes het 'n meer duidelike swelsel by geïnfekteerde wortelareas ingesluit. Selwande het verhard totdat die wortel radiaalsgewys versterk was met skierenchiem weefsel en nie-geleidende xileemvate terwyl die kutikula grootliks toegeneem het deur die groei van kurkagtige kambiumweefsel. Daar was geen direkte verwantskap tussen die bevolkingsdinamika van E. lanigerum en dié van Xiphinema en Pratylenchus nematodes nie. Die voorkoms van E. lanigerum was seisoenaal terwyl P. penetrans en Xiphinema se getalle onvoorspelbaar gefluktueer het. Onbeskadigde wortel stikstofvlakke het ooreengestem met die normale wortel groeisiklus. Stikstof vlakke van galwortels was noemenswaardig laer as dié van onbeskadigde wortels, heel waarskynlik as gevolg van voeding deur E. lanigerum. Grond ryk aan fyn sand en klei het groter bevolkings van E. lanigerum en Xiphinema onderhou as sanderige gronde. Die aantal E. lanigerum in grondmonsters het goed ooreengestem met die skade indeks wat aan die monsters toegeken was. Die aantal Xiphinema in grondmonsters het ook goed ooreengestem met die beskadigingsindeks wat aan die monsters toegeken is weens vermoedelike Xiphinema skade simptome. Beide Biostart 2000® en Furfural® was effektief as beheeragente van die appelbloedluis. Furfural'", 'n afvalproduk van die suikerriet industrie, was egter minder effektief as Biostart 2000®, 'n produk bestaande uit 'n aktiveerder en drie bakterie spesies, Bacillus laterosporus, B. chitinosporus en B. licheniformis. Die bakterië in die Biostart 2000® behandelde potte kon vermeerder onder gunstige toestande terwyl Furfural® na elke besproeiing verdun het. Biostart 2000® is ook makliker om aan te maak as Furfural® aangesien die bestanddele van Biostart 2000® geredelik meng tot 'n wateroplosbare pasta, terwyl Furfural® 'n olierige vloeistofis wat moeilik 'n waterige suspensie vorm. Wortelskade het plaasgevind kort nadat E. lanigerum begin voed het, alhoewel daar geen duidelike verwantskap tussen E. lanigerum en nematode spesies voorgekom het nie. Die mees belowende omgewingsvriendelike beheermaatreël was Biostart 2000®.

Thesis (MScAgric (Plant Pathology))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: A survey was undertaken on apple and pear trees in the Western Cape Province to determine the aetiology of trunk diseases with reference to trunk diseases occurring on grapevine. Grapevine trunk diseases cause the gradual decline and dieback of vines resulting in a decrease in the vine’s capability to carry and ripen fruit. In recent years, viticulture has been expanding into several of the well established pome fruit growing areas. The presence of trunk pathogens in pome fruit orchards may affect the health of the pome fruit trees as well as cause a threat to young vineyards planted in close proximity to these potential sources of viable inoculum. Several genera containing species known to be involved in trunk disease on pome fruit and grapevine were found, including Diplodia, Neofusicoccum, Eutypa, Phaeoacremonium and Phomopsis. Diplodia seriata and D. pyricolum, were isolated along with N. australe and N. vitifusiforme. Four Phaeoacremonium species, P. aleophilum, P. iranianum, P. mortoniae and P. viticola, two Phomopsis species linked to clades identified in former studies as Phomopsis sp. 1 and Phomopsis sp. 7, and Eutypa lata were found. In addition, Paraconiothyrium brasiliense and Pa. variabile, and an unidentified Pyrenochaetalike species were found. Of these the Phaeoacremonium species have not been found on pear wood and it is a first report of P. aleophilum occurring on apple. This is also a first report of the Phomopsis species and Eutypa lata found occurring on pome trees in South Africa Two new coelomycetous fungi were also found including a Diplodia species, Diplodia pyricolum sp. nov., and a new genus, Pyrenochaetoides gen. nov. with the type species, Pyrenochaetoides mali sp. nov., were described from necrotic pear and apple wood. The combined ITS and EF1-α phylogeny supported the new Diplodia species, which is closely related to D. mutila and D. africana. The new species is characterised by conidia that become pigmented and 1-septate within the pycnidium, and that are intermediate in size between the latter two Diplodia species. Phylogenetic inference of the SSU of the unknown coelomycete provided bootstrap support (100%) for a monophyletic clade unrelated to known genera, and basal to Phoma and its relatives. Morphologically the new genus is characterised by pycnidial with elongated necks that lack setae, cylindrical conidiophores that are seldomly branched at the base, and Phoma-like conidia. The phylogenetic results combined with its dissimilarity from genera allied to Phoma, lead to the conclusion that this species represents a new genus. A pathogenicity trial was undertaken to examine the role of these species on apple, pear and grapevine shoots. N. australe caused the longest lesions on grapevine shoots, while Pyrenochaetoides mali, Pa. variabile, D. seriata and P. mortoniae caused lesions that were significantly longer than the control inoculations. On pears, D. pyricolum and N. australe caused the longest lesions, followed by D. seriata and E. lata. On apples, the longest lesions were caused by N. australe and P. iranianum. D. seriata, D. pyricolum, E. lata, N. vitifusiforme, Pa. brasiliense, P. aleophilum and P. mortoniae also caused lesions on apple that were significantly longer than the control. The study demonstrated that close cultivation of grapevine to apple and pear orchards may have inherent risks in terms of the free availability of viable inoculum of trunk disease pathogens.
No Afrikaans abstract available.

3 pp.
Originally published: 2003
True mistletoes are parasitic flowering plants with characteristic clumps of growth that are easily visible on the host plant. They reduce the growth of infected hosts, but it usually takes many years for true mistletoe infections to kill a mature tree or shrub. This article gives information about the disease cycle, the symptoms and prevention and control methods for true mistletoes.

Thesis (PhD)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: Very little is known about the diversity of fungi associated with Afromontane forests of the Cape Floristic Region (CFR) of South Africa. The ophiostomatoid fungi include many species, some known as pathogens in the CFR, while others are well-known saprophytes important in wood degradation. This study focused on the biodiversity and ecology of tree-associated ophiostomatoid fungi (Ophiostomatales) in the CFR. In addition to this, mites and subcortical beetles associated with the CFR trees were collected, regardless of whether they were associated with ophiostomatoid fungi or not. A relatively high diversity of ophiostomatoid fungi were collected from native trees, ten of which were newly described here. Three further fungal species, two of which are probably new to science, were also collected from exotic Pinus species growing in these forests. Four Ophiostomatales species (including three newly described species) were associated with subcortical beetles on Rapanea melanophloeos and Olea capensis ssp. macrocarpa. These were Sporothrix pallida, Sporothrix aemuluphilus, Raffaelea scabbardiae and Raffaelea rapaneae, associated with the beetles Lanurgus sp. 1, Ctonoxylon sp. 1, Xyleborinus aemuluphilus and a Platypodinae species. This represents a first study to explore the associations between subcortical beetles and ophiostomatoid fungi on native trees in the CFR. In addition to fungi associated with subcortical beetles, several members of the Ophiostomatales associated with wounds on Rapanea melanophloes trees were also collected. These included Ophiostoma stenoceras, Sporothrix reniformis, S. rapaneae, S. lunateae and S. noisomeae. All but O. stenoceras were new to science, and were formally described here. All of these wound-associated species from R. melanophloeos belong to the Sporothrix schenckii – O. stenoceras complex, except for S. noisomeae that was provisionally placed in the S. lignivora complex. Besides fungal taxa collected from wounds on Rapanea melanophloeos, other fungi were also collected from wounds on other host trees species. Three more previously undescribed ophiostomatoid fungal species were collected from this niche. They included Sporothix capensis collected from O. capensis ssp. macrocarpa, Graphilbum roseus collected from many different, unrelated host trees and Graphium ilexiense (Microascales), isolated from wounds on Ilex mitis. The latter represented the first isolation of an ophiostomatoid fungus from this host tree species. Two possibly new fungal species (Sporothrix sp. 1, Ceratocystiopsis sp. 1) and Ophiostoma ips, associated with three bark beetles (Orthotomicus erosus, Hylurgus ligniperda and Hylastes angustatus), were collected from Pinus. Several fungal species were collected from both native trees and non-native trees. These included Sporothrix fusiforme from Brabejum stellatifolium and Acacia mearnsii, O. quercus and O. pluriannulatum-like fungus from several native trees and from A. mearnsii. This suggests a possibility for host shifting of some of these fungi between native and non-native hosts or even between different native hosts. Eight non-ophiostomatoid fungi associated subcortical beetles taxa were found also to infest native trees in the Afromontane forests and in total more than 4500 beetle individuals were collected. Some species of ophiostomatoid fungi collected in this study were found to be associated with other arthropods such as mites. Four phoretic mites species associated with ophiostomatoid fungi (Dendrolaelaps quadrisetus, Histiogaster sp. 3, Elattoma sp. 1 & 2) were collected. In addition, sixteen species of tree wound-associated mites were collected from 12 native trees. Of these, nine were associated with several ophiostomatoid fungi (Graphilbum roseus, O. pluriannulatum-like, O. quercus) that were isolated from several different host trees. This suggests that they may aid in the transport of these fungi from one host species to another. The possible consequences of transfers of Ophiostomatales species between hosts were tested using pathogenicity tests, which highlighted that some fungi are pathogenic on several different trees. Transfers seemed most likely in fungal species isolated from wounds, especially those associated with mites, because the mites may aid in the vectoring of these. When phoretic mites were tested for their specificity to their vector beetles, they proved to be highly specific. Although some of the fungi associated with these mites and their sub-cortical beetles were also pathogenic, it is less likely for these fungi to be transferred to other host tree species due to the high specificity of their arthropod associates. This study represents one of a few studies that focused on ophiostomatoid fungi, subcortical beetles and mites associated with trees in the Afromontane forests of South Africa. Although we collected a high diversity of Ophiostomatales members, many more still await discovery. It is recommended that future studies focus on the complex inter-organismal interactions in many of the systems uncovered in this study.
AFRIKAANSE OPSOMMING: Baie min is bekend oor die diversiteit van fungi wat met die Afromontane woude van die Kaapse Floristiese Streek (KFS) van Suid Afrika geassosieer is. Die ophiostomatoïde fungi sluit baie spesies in, sommiges bekend as patogene in die KFS, terwyl ander bekende en belangrike saprofiete in houtdegradasie is. Hierdie studie het op die biodiversiteit en ekologie van die boom-geassosieerde ophiostomatoïde fungi (Ophiostomatales) in die KFS gefokus. Daarbenewens is myte en subkortikale kewers wat met die KFS bome geassosieer word ook versamel, ongeag of hulle geassosieerd was met ophiostomatoïde fungi of nie. „n Relatief hoë diversiteit van ophiostomatoïde fungi is van inheemse bome versamel, tien waarvan hier nuut beskryf is. Drie verdere fungi spesies, twee waarvan ook waarskynlik nuut is tot die wetenskap, is ook vanaf Pinus spesies versamel wat in hierdie woude gegroei het. Vier Ophiostomatales spesies (insluitend drie nuut beskryfde spesies) wat met subkortikale kewers op Rapanea melanophloeos en Olea capensis L. ssp. macrocarpa geassosieer is, is ook versamel. Hulle was Sporothrix pallida, Sporothrix aemuluphilus, Raffaelea scabbardiae en Raffaelea rapaneae, geassosieer met die kewers Lanurgus sp. 1, Ctonoxylon sp. 1, Xyleborinus aemuluphilus en „n Platypodinae spesie. Hierdie verteenwoordig die eerste studie wat die assosiasies tussen subkortikale kewers en ophiostomatoïde fungi op inheemse bome in die KFS ondersoek. Addisioneel tot fungi geassosieer met die subkortikale kewers, is verskeie lede van die Ophiostomatales vanaf wonde op Rapanea melanophloes bome versamel. Hulle sluit in Ophiostoma stenoceras, Sporothrix reniformis, S. rapaneae, S. lunateae en S. noisomeae. Almal behalwe O. stenoceras was nuut tot die wetenskap, en is hier formeel beskryf. Al hierdie wond-geassosieerde spesies vanaf R. melanophloeos behoort aan die Sporothrix schenckii – O. stenoceras kompleks, behalwe vir S. noisomeae wat voorlopig in die S. lignivora kompleks geplaas is. Benewens fungi taxa wat van die wonde op Rapanea melanophloes versamel is, is ander fungi ook vanaf die wonde op ander gasheer boom spesies versamel. Drie verdere ophiostomatoïde fungus spesies is in hierdie nis versamel. Hulle sluit in Sporothix capensis wat vanaf O. capensis ssp. macrocarpa versamel is, Graphilbum roseus wat vanaf baie verskillende, onverwante gasheer bome versamel is en Graphium ilexiense (Microascales), wat vanaf wonde op Ilex mitis versamel is. Laasgenoemde verteenwoordig die eerste isolasie van „n ophiostomatoïde fungus vanaf hierdie gasheer boom spesie. Twee moontlik nuwe fungus spesies (Sporothrix sp. 1, Ceratocystiopsis sp. 1) en Ophiostoma ips, geassosieer met drie baskewers (Orthotomicus erosus, Hylurgus ligniperda en Hylastes angustatus) is vanaf Pinus versamel. Verskeie fungi spesies is van beide inheemse en nie-inheemse bome versamel. Hulle het Sporothrix fusiforme vanaf Brabejum stellatifolium en Acacia mearnsii, O. quercus en O. pluriannulatum-like fungus vanaf verskeie inheemse bome en vanaf A. mearnsii ingesluit. Dit suggereer die moontlikheid van gasheer-skuiwing van sommige van hierdie fungi tussen inheemse en uitheemse gashere of selfs tussen verskillende inheemse gashere. Agt nie- ophiostomatoïde geassosieerde subkortikale kewers was ook versamel en in totaal is meer as 4500 kewer indiwidue versamel. Sommige ophiostomatoïde fungus spesies wat in hierdie studie versamel is, was met ander geleedpotiges soos myte geassosieer. Vier foretiese myt spesies wat met ophiostomatoïde fungi geassosieer is (Dendrolaelaps quadrisetus, Histiogaster sp. 3, Elattoma sp. 1 & 2), is versamel. Nege addisioneële myt spesies was met verskeie ophiostomatoïde spesies vanaf verskeie boomspesies geassosieer (Graphilbum roseus, O. pluriannulatum-like, O. quercus). Dit suggereer dat myte die vervoer van hierdie fungi van een gasheer spesie na die ander mag bewerkstellig. Die moontlike gevolge van die oordrag van Ophiostomatales spesies tussen gashere is getoets deur patogeniteitstoetse. Dit het beklemtoon dat sommige fungi patogenies is op verskeie onverwante boomspesies. Oordraag van spesies is mees waarskynlik in fungi spesies wat vanaf wonde geisoleer is, veral dié wat met myte geassosieer is, want die myte mag hierdie fungi help vervoer. Toe foretiese myte getoets is vir hulle spesifisiteit tot hulle vektore, is hulle hoogs spesifiek bevind. Alhoewel sommige fungi wat met hierdie myte en hulle geassosieerde kewers geassosieer word wel patogenies is, is dit minder waarskylik dat hulle na ander gasheer bome sal verskuif as gevolg van die hoë spesifisiteit van hulle geleedpotige assosiate. Hierdie studie verteenwoordig een van net enkele studies gefokus op ophiostomatoïde fungi, subkortikale kewers en myte wat met bome van die Afromontane woude van Suid-Afrika geassosieer is. Alhoewel ons „n hoë diversiteit van Ophiotomatale lede versamel het, wag baie meer fungi spesies waarskynlik nog op ontdekking. Daar word voorgestel dat toekomstige studies fokus op die komplekse inter-organismiese interaksies in baie van die sisteme wat in hierdie studie blootgelê is.

Made available in DSpace on 2014-06-11T19:35:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2004-02-17Bitstream added on 2014-06-13T18:45:55Z : No. of bitstreams: 1 ottati_alt_dr_botfca.pdf: 651467 bytes, checksum: a1b92614d7fbcfa2a73dbf3cf0eb427b (MD5)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Universidade Estadual Paulista (UNESP)
Empresa Privada
Os afídeos são um dos grupos de pragas amplamente distribuídos, causando perdas consideráveis em sistemas agrícolas e florestais. O pulgão-gigante-do-pinus, Cinara atlantica, é atualmente a espécie de pulgão mais disseminada nos plantios de Pinus no Brasil. Devido à sua importância econômica, esse trabalho objetivou avaliar o efeito de diferentes temperaturas e da espécie hospedeira no desenvolvimento de ninfas e na longevidade e capacidade reprodutiva de adultos de C. atlantica, sob condições de laboratório, e determinar a flutuação populacional, a estrutura etária e a caracterização da estrutura espacial do afídeo em áreas florestadas com Pinus taeda e P. caribaea var. caribaea. A determinação do efeito de diferentes temperaturas (18o C, 22o C, 26o C e 30o C) e de hospedeiros (P. taeda e P. caribaea var. hondurensis) no desenvolvimento de C. atlantica foi conduzida sob fotofase de 12 h e umidade relativa do ar de 70 10%. Utilizaram-se 20 insetos (repetições) para cada combinação dos fatores temperatura e hospedeiro e obtiveram-se resultados para variáveis nos estágios ninfal e adulto e ciclo de vida. A determinação da flutuação populacional e da caracterização espacial (50 árvores/avaliação) e da estrutura etária (cinco colônias/avaliação) de C. atlantica foi realizada em áreas de 1 ha com P. taeda e P. caribaea var. caribaea nos municípios de Buri e Nova Campina/SP em 21 avaliações entre julho de 2001 e agosto de 2002. Concluiu-se que o desenvolvimento de ninfas e a longevidade e potencial reprodutivo dos adultos de C. atlantica não foram influenciados pelos hospedeiros P. taeda e P. caribaea var. hondurensis. Entretanto, as temperaturas constantes de 18o C e 22o C conferem as melhores condições, enquanto a de 30o C as piores condições de desenvolvimento aos insetos mantidos em P. taeda e P. caribaea var. hondurensis. C. atlantica... .
Aphids are one of the most widespread groups of pests, causing severe damages on agricultural and forestry systems. Nowadays, the giant conifer aphid, C. atlantica, is widely distributed on pine forests in Brazil. Due to its economic importance, this study aimed to evaluate the effects of different constant temperatures and host plants on the development of nymphs and adults and reproductive capacity in adult of C. atlantica in laboratory, monitoring the populational fluctuation, the age structure and to characterize spatial pattern of C. atlantica in Pinus taeda and P. caribaea var. caribaea plantations. The effect of constant temperatures (18o C, 22o C, 26o C e 30o C) and host plants (P. taeda and P. caribaea var. hondurensis) on the development of C. atlantica was carried out at 12 h of photophase (12 h) and 70 + 10% relative humidity. Twenty nymphs (replications) were tested for each treatment (temperature x host plant) to estimated biological variables of nymph and adult stages and life span. The study of the populational fluctuation, the spatial characterization (50 trees sampled per sampling date) and the age structure (5 aphid colonies per sampling date) of C. atlantica was carried out on P. taeda and P. caribaea var. caribaea plantations in 1 ha area in Buri and Nova Campina municipalities (SP, Brazil), between July 2001 and August 2002 (21 sampling dates). This research indicated that nymph and adult development and reproductive capacity of C. atlantica were not affected by host plants. However, temperatures of 18o C and 22o C provided better conditions for aphid development than 30o C when reared on P. taeda and P. caribaea var. hondurensis. In the field, C. atlantica had highest peaks of abundance in the winter and spring and lowest during the summer. The age structure study can give support to predict population peaks and the occurrence of stable populations indicates a low... (Complete abstract, click electronic address below).

Submitted by Milena Rubi (milenarubi@ufscar.br) on 2017-08-08T17:44:33Z No. of bitstreams: 1 GHIOTTO_Thais_2016.pdf: 18907197 bytes, checksum: 0779f8ac869df152bdd7747df97a15e5 (MD5)
Approved for entry into archive by Milena Rubi (milenarubi@ufscar.br) on 2017-08-08T17:44:43Z (GMT) No. of bitstreams: 1 GHIOTTO_Thais_2016.pdf: 18907197 bytes, checksum: 0779f8ac869df152bdd7747df97a15e5 (MD5)
Approved for entry into archive by Milena Rubi (milenarubi@ufscar.br) on 2017-08-08T17:44:49Z (GMT) No. of bitstreams: 1 GHIOTTO_Thais_2016.pdf: 18907197 bytes, checksum: 0779f8ac869df152bdd7747df97a15e5 (MD5)
Made available in DSpace on 2017-08-08T17:44:55Z (GMT). No. of bitstreams: 1 GHIOTTO_Thais_2016.pdf: 18907197 bytes, checksum: 0779f8ac869df152bdd7747df97a15e5 (MD5) Previous issue date: 2016-05-09
Não recebi financiamento
Megastigmus transvaalensis is an exotic wasp that attacks Brazilian pepper tree drupes Schinus terebinthifolius in native forests and areas of restoration and ecological restoration in Brazil. The parasitism begins with the oviposition M. transvaalensis in drupes S. terebinthifolius where the larvae hatch and remain internally feeding of nutrients and tissue, affecting germination. The aim of this work was to study the effect of temperature, rainfall and humidity in the population dynamics of M. transvaalensis and determine the parasitism rate and sex ratio of this wasp in drupes S. terebinthifolius. The study was performed with yellow sticky traps and collection of S. terebinthifolius drupes in seasonal semideciduous forest during August 2014 to September 2015, in the region of Sorocaba, São Paulo, Brazil. The capture of insects through the sticky traps proved satisfactory, and thus can be applied to the monitoring of small Hymenopteros. Populations of M. transvaalensis were negatively correlated with the maximum temperature and population peak in the fall of 2015, meaning that when the maximum temperature has reduced, there is a higher incidence of insect field. The parasitism rate of S. terebinthifolius drupes ranged from zero to 36.34% during this period, making this value an aggravating factor for the emergence of new individuals, since this phytophagous wasp has the potential to be spread throughout Brazil and It poses a threat to the natural regeneration of S. terebinthifolius. The sex ratio of M. transvaalensis was 0.42 and 0.08 in the laboratory field. The bio-ecology and the damage caused by M. transvaalensis in drupes S. terebinthifolius warrant further studies to integrated management
Megastigmus transvaalensis é uma vespa exótica que ataca drupas de aroeira-pimenteira Schinus terebinthifolius em florestas nativas e em áreas de recomposição e restauração ecológica no Brasil. O parasitismo inicia com a oviposição de M. transvaalensis nas drupas de S. terebinthifolius, onde as larvas internamente eclodem e permanecem alimentando-se dos nutrientes e tecidos, prejudicando a germinação. O objetivo desse trabalho foi estudar o efeito da temperatura, precipitação e umidade na flutuação populacional de M. transvaalensis e determinar o índice de parasitismo e razão sexual dessa vespa nas drupas de S. terebinthifolius. O estudo foi realizado com armadilhas adesivas amarelas e coleta de drupas de S. terebinthifolius em fragmento de floresta estacional semidecidual, durante agosto de 2014 a setembro de 2015, na região de Sorocaba, São Paulo, Brasil. A captura dos insetos através das armadilhas adesivas se mostrou satisfatória, podendo assim ser aplicada para o monitoramento de pequenos Hymenopteros. As populações de M. transvaalensis apresentaram correlação negativa com a temperatura máxima e pico populacional no outono de 2015, significando que, quando a temperatura máxima apresenta redução, há maior incidência do inseto em campo. O índice de parasitismo das drupas de S. terebinthifolius variou de zero a 36,34% no período avaliado, tornando este valor um agravante para o surgimento de novos indivíduos, uma vez que, essa vespa fitófaga tem potencial de ser disseminado por todo Brasil e representa ameaça para a regeneração natural de S. terebinthifolius. A razão sexual de M. transvaalensis foi de 0,42 no laboratório e 0,08 em campo. A bioecologia e os danos causados por M. transvaalensis em drupas de S. terebinthifolius justificam mais estudos visando o manejo integrado dessa vespa fitófaga.

Orientador: Carlos Frederico Wilcken
Banca: Carlos Alberto Hector Flechtmann
Banca: Célia Regina Lopes Zimback
Banca: Sonia Maria Noemberg Lazzari
Banca: Carlos Alberto Fleichmann
Banca: Edson Tadeu Iede
Resumo: Os afídeos são um dos grupos de pragas amplamente distribuídos, causando perdas consideráveis em sistemas agrícolas e florestais. O pulgão-gigante-do-pinus, Cinara atlantica, é atualmente a espécie de pulgão mais disseminada nos plantios de Pinus no Brasil. Devido à sua importância econômica, esse trabalho objetivou avaliar o efeito de diferentes temperaturas e da espécie hospedeira no desenvolvimento de ninfas e na longevidade e capacidade reprodutiva de adultos de C. atlantica, sob condições de laboratório, e determinar a flutuação populacional, a estrutura etária e a caracterização da estrutura espacial do afídeo em áreas florestadas com Pinus taeda e P. caribaea var. caribaea. A determinação do efeito de diferentes temperaturas (18o C, 22o C, 26o C e 30o C) e de hospedeiros (P. taeda e P. caribaea var. hondurensis) no desenvolvimento de C. atlantica foi conduzida sob fotofase de 12 h e umidade relativa do ar de 70 10%. Utilizaram-se 20 insetos (repetições) para cada combinação dos fatores temperatura e hospedeiro e obtiveram-se resultados para variáveis nos estágios ninfal e adulto e ciclo de vida. A determinação da flutuação populacional e da caracterização espacial (50 árvores/avaliação) e da estrutura etária (cinco colônias/avaliação) de C. atlantica foi realizada em áreas de 1 ha com P. taeda e P. caribaea var. caribaea nos municípios de Buri e Nova Campina/SP em 21 avaliações entre julho de 2001 e agosto de 2002. Concluiu-se que o desenvolvimento de ninfas e a longevidade e potencial reprodutivo dos adultos de C. atlantica não foram influenciados pelos hospedeiros P. taeda e P. caribaea var. hondurensis. Entretanto, as temperaturas constantes de 18o C e 22o C conferem as melhores condições, enquanto a de 30o C as piores condições de desenvolvimento aos insetos mantidos em P. taeda e P. caribaea var. hondurensis. C. atlantica... (Resumo completo, clicar acesso eletrônico abaixo).
Abstract: Aphids are one of the most widespread groups of pests, causing severe damages on agricultural and forestry systems. Nowadays, the giant conifer aphid, C. atlantica, is widely distributed on pine forests in Brazil. Due to its economic importance, this study aimed to evaluate the effects of different constant temperatures and host plants on the development of nymphs and adults and reproductive capacity in adult of C. atlantica in laboratory, monitoring the populational fluctuation, the age structure and to characterize spatial pattern of C. atlantica in Pinus taeda and P. caribaea var. caribaea plantations. The effect of constant temperatures (18o C, 22o C, 26o C e 30o C) and host plants (P. taeda and P. caribaea var. hondurensis) on the development of C. atlantica was carried out at 12 h of photophase (12 h) and 70 + 10% relative humidity. Twenty nymphs (replications) were tested for each treatment (temperature x host plant) to estimated biological variables of nymph and adult stages and life span. The study of the populational fluctuation, the spatial characterization (50 trees sampled per sampling date) and the age structure (5 aphid colonies per sampling date) of C. atlantica was carried out on P. taeda and P. caribaea var. caribaea plantations in 1 ha area in Buri and Nova Campina municipalities (SP, Brazil), between July 2001 and August 2002 (21 sampling dates). This research indicated that nymph and adult development and reproductive capacity of C. atlantica were not affected by host plants. However, temperatures of 18o C and 22o C provided better conditions for aphid development than 30o C when reared on P. taeda and P. caribaea var. hondurensis. In the field, C. atlantica had highest peaks of abundance in the winter and spring and lowest during the summer. The age structure study can give support to predict population peaks and the occurrence of stable populations indicates a low... (Complete abstract, click electronic address below).
Doutor

Pine wilt disease is the result of a complex interaction between a nematode, a host tree and an insect vector. The pine wood nematode (PWN) Bursaphelenchus xylophilus (Steiner and Buhrer) Nickle is the causal agent, being pines the most important hosts. To be dispersed between hosts the nematode requires a vector insect, being the most effective the cerambycid beetles of the genus Monochamus Dejan. The first detection of PWN in Portugal occurred in 1999, and in 2001 it was associated with its local vector; the pine sawyer Monochamus galloprovincialis (Olivier). Since then M. galloprovincialis has been the main focus of a complex and detailed strategic plan to fight this disease. Management and control strategies against PWN are directed in three ways; controlling the nematode’s populations; creation of trees resistant to the disease and avoiding the spread of the nematode by the dispersal of vector insects, being presently the most effective one. This is done with the implementation of strict sanitary measures in affected forests, by locating, felling and removing/destroying symptomatic trees during autumn and winter, to prevent adult emergences carrying the PWN. During spring and summer, M. galloprovincialis adults are exhaustively controlled by the use of baited traps, diminishing beetles populations. Despite such efforts, the PWN still causes significant mortality in native maritime pine forests in Portugal, and between 2000 and 2007 the number of felled pine trees with wilting symptoms significantly increased, causing significant economic and environmental impacts. Simultaneously, the spread of wilt disease to Spain underlines the necessity to develop and promote innovative control strategies against this sanitary problem. With the intention of developing new biological control strategies, the works here presented were focused on: i) improving a laboratory reared population of M. galloprovincialis, ii) reveal M. galloprovincialis actual distribution and the associated parasitoid guild, iii) discover the most promising entomopathogenic fungi associated with this insect and an effective method for field application. The initial studies concerning the artificial rearing of a laboratory population of M. galloprovincialis allowed the attainment of adults on shorter periods and with less effort. Such objective was successfully accomplished by the development of an artificial rearing substrate which is cheaper to produce and does not require fresh pine material recently extracted from live trees. Concerning the unveil of the insect distribution across the country and its parasitoid guild, it was found that the cerambycidae is present on more than 90% of the surveyed regions, without showing signs of strong susceptibilities to the edaphoclimatic variations of each site. Also, the parasitoid guild associated with this insect showed to be relatively disperse and diverse across the studied regions. Most of the parasitoids found were larval parasitoids, being the most common among them Cyanopterus flavator (Fabricius). Regarding the assays with entomopathogenic fungi, it was revealed that Beauveria bassiana (Bals.-Criv.) Vuill was an important mortality agent for M. galloprovincialis adults while Metarhizium sp. strongly affected the larvae of this insect. A successful application method was also developed using fiber bands to impregnate entomopathogenic fungi under laboratory conditions. It is now possible to state that it was comprehensively studied the parasitoid guild associated with the pine sawyer and the effects of the more common entomopathogenic fungi found in Portugal and associated with this beetle, being now unveiled the basis for a biological control program against M. galloprovincialis populations.
La enfermedad del decaimiento súbito del pino (Pine Wilt Disease, PWD) consiste en una interacción entre tres organismos; el nematodo Bursaphelencus xylophilus (Steiner y Buhrer) Nickle, un insecto vector del genero Monochamus Dejan, y un árbol huésped del género Pinus Linnaeus. Se cree que la enfermedad llegó a Portugal en 1999 a través de la entrada de madera contaminada proveniente de China. En Europa, Portugal es el único país con una gran área de árboles afectados por esta enfermedad, siendo el único huésped el pino marítimo (Pinus pinaster Aiton). La entrada del nematodo en un árbol sano suele llevar a su muerte en algunos meses o mismo semanas y en este país, su principal insecto vector pertenece a la especie Monochamus galloprovincialis (Olivier). Las técnicas actualmente existentes para combatir esta enfermedad son en gran parte basada en metodologías biotécnicas, químicas y culturales para disminuir las poblaciones del insecto, todavía estas medidas no fueron suficientes, pues en el bienio de 2011/2012 aproximadamente 900.000 árboles fueron identificadas como portadores de síntomas de PWD y cortados en el terreno. Su detección en España enfatiza la necesidad de descubrir nuevos métodos de control. Con este objetivo en mente se desarrollaron los trabajos presentados en esta tesis. Se prospectó el país para encontrar la actual distribución del insecto, el complejo de enemigos naturales nativos, y los hongos entomopatógenos que lo afectan. La prospección ha demostrado que este insecto se encuentra ampliamente distribuido por todo el territorio. Juntamente, se descubrió que existen 14 especies de parasitoides en la región Paleártica que pueden afectar esta escarabajo. Los resultados de los ensayos con hongos entomopatógenos demostraron que la especie Beauveria bassiana (Bals.-Criv.) Vuill suele ser más eficaz en el control de adultos de mientras que Metarhizium sp. afecta más los estadios larvales. La técnica de aplicación de estos hongos utilizando bandas de polyester impregnadas con esporos demostró también resultados muy promisores. Se puede considerar que se estudiaron algunos elementos esenciales de un futuro programa de control biológico contra M. galloprovincialis.

Bibliography: leaves 169-185
viii, 185 leaves, [1] leaf of plates : ill. (some col.) ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Pathology, 1987

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg in fulfillment of the requirements for the degree Master of Science Johannesburg, 2018
Seed recalcitrance in avocado (Persea americana) has meant that avocado genetic material cannot be conserved in orthodox seed banks. Thus, biotechnological approaches have been considered for the long-term conservation of this species’ genetic material, through the cryopreservation of tissue culture-generated axillary buds. A study was conducted to develop a system for the proliferation of in vitro avocado cv. ‘Edranol’ axillary buds for the purpose of cryopreservation. Experiments were conducted to optimise avocado mother plant establishment and pretreatment. It was determined that potting soil mixes comprising of either 1:1:1 pine bark, perlite, river sand or 1:1:1 peat, perlite, river sand were suitable to culture healthy avocado mother plant seedlings. With these soil mixes approximately 2 shoots per plant developed after 11 weeks of transplanting and between 2.9 ± 0.31 and 3.37 ± 0.32 secondary shoots were produced after 5 months. Additionally, the mother plants produced well extended shoots (7.30 ± 1.29 cm; 8.77 ± 1.39 cm) with a sufficient number of axillary buds (7.75 ± 0.39; 6.33 ± 0.53), which were subsequently used as nodal explants. After surface decontamination, the establishment of an aseptic culture in vitro was successfully achieved. Six semi-solid tissue culture media were tested for the proliferation of in vitro axillary buds. Four media comprised of half (½) and full strength Murashige and Skoog (MS) medium (Murashige and Skoog, 1962), with either 0.5 or 1mg/l 6-Benzylaminopurine (BAP). Two media were based on the P. indica medium as proposed by Nel et al. (1983), and comprised of half strength MS macronutrients, full strength MS micronutrients, 2mg/l BAP and 1mg/l GA3. All media were supplemented with 3g/l Gelrite and 30g/l sucrose at pH 5.6-5.8. Physiological measurements were taken six weeks after establishment, the first, the second and the third subculture. Tissue browning, death and contamination were observed in explants cultured on the media containing 0.5mg/l BAP, suggesting that this concentration of BAP was not suitable for cv. ‘Edranol’. Additionally, hyperhydricity appeared to be associated with the media containing ½ MS, which could be attributed to mineral deficiencies. Overall, there was no significant difference in the number of shoots and axillary buds developed across all the media tested, suggesting that endogenous auxin levels were higher than the concentration of cytokinin used in the media tested. In support of this, strong apical dominance and callus formation was observed. An increase in tissue browning, death and hyperhydricity on all the media tested, coupled with a decrease in shoot length, suggested a decline in the vigour of explants in vitro. 1MS + 1mg/l BAP was selected as the most appropriate medium for the initiation of cv. ‘Edranol’ cultures, producing between 3.2 ± 0.2 and 4.9 ± 0.5 axillary buds per explant. However, hyperhydricity, browning and death were observed in explants cultured on this medium. Overall, the in vitro axillary bud explants did not behave predictably or uniformly. Thus, the system was not optimised, indicating that further study is needed for the mass multiplication of axillary buds to be used for the cryo-conservation of avocado genetic material. It is recommended that future experiments will be needed to further test tissue culture media, with a focus on the optimisation of the nutrient and plant growth regulator concentrations. Additionally, the recalcitrance of explants to the in vitro environment may have been influenced by the physiological state of the mother plants, indicating that research should be focused on the effect which the mother plants may have on the endogenous responses of the in vitro explants.
MT 2018

Fruit-tree borer, Maroga melanostigma (Wallengren), is a native Australian pest in many species of trees. It is of particular economic importance in prune (Prunus domestica) trees because the presence of this wood boring insect can reduce productivity by an average of 5% per tree. Large areas of orchards can be affected. There are currently no chemicals registered for control of this pest. Young, New South Wales is the second largest prune-growing district in Australia and the area most seriously affected by M. melanostigma. Prune growers in the district utilise integrated pest management and were supportive of a project to investigate biological control options for this economically damaging pest. The two main objectives of the project were 1) to understand the life cycle of M. melanostigma, so biological controls could be timed appropriately; and 2) to investigate biological control options for this pest. Life cycle studies were commenced in the first season (2003/04) using field cages and light trapping. These investigations continued throughout the project. In Young, moths were found to emerge from wood over a two month period (December and January). Oviposition was assumed to be during this period however, even after extensive searches of trees, no eggs were observed. Historical data were collated to determine locations and timings of moth emergence elsewhere in Australia. The data showed that M. melanostigma has been found in every state and territory Australia, with moths observed from October through to March. The biological control options reviewed were egg parasitoids (Trichogramma species only), entomopathogenic nematodes and entomopathogenic fungi. Trichogramma were favoured because of previous research undertaken against the same pest in pecans in Moree, NSW. Entomopathogenic nematodes were also investigated due to research indicating their effectiveness in cryptic situations, such as borer tunnels in trees. Fungi were considered but dismissed due to lack of literature supporting their effectiveness in reducing lepidopteran pest damage in trees. A major field trial was designed with the assistance of a biometrician and the trial blocks laid out based on this advice. There were three trial sites, each containing four blocks of approximately 200 trees (~800 trees/site). Two blocks were designated as release blocks and two as non-release blocks to correspond with the trial’s two treatments. In the first season (2003/04) an initial visual assessment of borer damage was undertaken after leaf fall on each of the trees in the trial. This information was used as baseline data, to compare against damage levels following biological control releases in the second and third years of the project. Natural parasitism in the field was assessed using cultured eggs of Helicoverpa armigera (Hübner) before and between Trichogramma carverae (Oatman and Pinto) releases. Temperature and relative humidity were recorded in each of the trial sites, for the duration of the trial, using commercially available data loggers. In the second season (2004/05), Trichogramma releases were made during the period of moth activity and H. armigera eggs were used to monitor parasitism in the trial orchards. Parasitised eggs were reared through and all parasitoids were identified as T. carverae. Damage assessments were again carried out after leaf fall to compare release versus non-release blocks, as well as to determine if there was any change in borer activity. Early instar larvae were collected from non-trial blocks and exposed to the entomopathogenic nematode Steinernema carpocapsae in a laboratory investigation. Results from this limited bioassay were inconclusive. In the third season (2005/06), Trichogramma releases were again made during the period of moth activity and H. armigera eggs were used to monitor parasitism in the trial orchards. Parasitised eggs were reared through to emergence. The emerged parasites were identified as T. carverae, T. pretiosum and T. nr brassicae. Damage assessments were again made of all the trees in the trial. Results were statistically analysed to detect any differences between treatments. There was no statistically significant evidence that the releases of T. carverae reduced damage from M. melanostigma over the duration of the trial. Although damage increased across both release and non-release treatments in most blocks during the trial investigations, the increase was slightly lower in trees in which Trichogramma had been released. It should be noted that the experiments were affected by serious drought conditions which prevailed during the three seasons of the trial.
Master of Science (Hons)

Rodents cause damage in commercial forests by gnawing at the bark of the trees. It is currently estimated that rodent damage in commercial forestry costs the industry R50 million per annum. The species of rodents which cause the damage are not known, neither is the reason behind this behaviour. Through stomach analysis it has been established that 3 species are involved Otomys irroratus, Rhabdomys pumilio and Mastomys natalensis, however this behaviour is confined to the winter. Chemical analysis of the bark reveals that the percentage concentration of nitrogen varies seasonally. The period of high concentration correlates with periods when the natural food of the rodents is restricted and when bark gnawing is most prevalent. In the past the industry's response to the damage has been to treat the areas with rodenticides. Using standard CMR methods, the two commercially-licensed rodenticides and raptor perches were tested to examine their efficacy as rodent control strategies. It was found that at a lower application of I block of rodenticide every third tree there is little difference in the effectiveness of the rodenticide brands and there is also little reduction in the abundance of the rodents. At a higher application rate of I block per tree, the abundance of rodents is reduced but termination of the treatment results in the rodent numbers quickly recovering, indeed they surpassed their original population numbers within 4 months. Apart from the environmental dangers of applying such concentrations of poison, this is clearly an uneconomic solution. My results indicate that at first planting, the sites should be provisioned with raptor perches at a density of 16 ha⁻². Contrary to accepted policy the perches do not require cross pieces, which add to the expense and offer no advantage in raptor residency time. In areas of very high rodent abundance the provisioning of tree collars provide physical protection to the trees. An additional benefit of the collars is that the collars cause a beneficial microclimate around the tree which enhances its growth rate. When the tree is around 2 years old it should be pruned to a height of I ffi, the slash being left in the inter-row. Results show that trees treated in such a way experience no further attack and the rodents browse on the prunings. As the cost of the perches is reduced and the cost of pruning is non-recurring the recommendations provide an economical and environmentally sympathetic alternative to rodenticide application.
Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1996.

The anthracnose pathogen, Colletotrichum gloeosporioides (Penz.) Penz. & Sacc., is a major cause of disease in the avocado industry, causing significant economic losses, and infects all cultivars. In South Africa, Fuerte and Hass varieties are the most widely grown. Identification of genes differentially expressed in avocado during infection with the fungus represents an important step towards understanding the plant’s defence responses and would assist in designing appropriate intervention strategies. In this study, 454 sequencing and analysis of the transcriptome of infected Fuerte avocado fruits were performed using the Roche 454 GS FLX Titanium platform. cDNA libraries enriched for differentially expressed genes were constructed from unharvested and harvested avocado fruit tissues collected after 1, 4 and 24 h post-infection and after 3, 4, 5 and 7 day post-infection, then sequenced.The expression profiles of the genes expressed were measured by a hierarchical clustering algorithm.Subsequently, quantitative real-time PCR was employed to measure the expression of some candidate resistance genes to anthracnose disease and to validate the sequencing results. The single sequencing run produced 215 781 reads from the transcriptome. A total of 70.6 MB of sequence data was generated and subjected to BLAST searches of which about 1500 genes encoding proteins predicted to function in signal transduction, transcriptional control, metabolism, defence, stress response, transportation processes and some genes with unknown functions were identified. The expression profiles studies showed that many expressed genes were either up or down regulated after infection in avocado fruits when compared to the uninfected sample. Salicylic acid and ethylene were identified to be involved in the signalling networks activated in avocado fruit during C. gloeosporioides infection. This study showed that avocado is able to respond to C. gloeosporioides infection by exhibiting a sophisticated molecular system for pathogen recognition and by activating structural and biochemical defence mechanisms.

The shake and wash technique (samples placed in a jar with alcohol added and shaken to remove the mites) was effective in removing 100% of the predator mites, and adult spruce spider mites from Douglas-fir foliage and 98% of the spruce spider mite nymphs. Eighty-eight percent of the spruce spider mite eggs was removed. This technique was considered efficient for removal of spruce spider mite and its predators from Douglas-fir foliage. Sodium hypochlorite (0.84%) added to the alcohol did not increase the number of spruce spider mites or phytoseiid mites removed from the foliage. The intracanopy distribution of spruce spider mite and its predator mites was studied on Douglas-fir Christmas trees in the Willamette Valley, Oregon. When overwintering spruce spider mite egg densities populations were low (<5 eggs/19 cm of stem), significantly more eggs were found on the current season's growth. No significant differences were found between top and bottom halves of the tree or between compass directions. Differences between current and previous season's growth were not found when egg densities were high (>40 eggs/19 cm of stem), but significant differences were found between levels for current season's growth with more eggs found in the upper portion of the canopy. Quadri-directional differences did not exist with either low or high mite populations. Sampling tip or basal stem-halves with low overwintering egg populations did not bias population estimates. Heavy spring rainfall appeared to reduce mite populations as has been reported elsewhere by washing them off the tree and causing increased mortality. Spruce spider mite disperse to the current season's growth shortly after budbreak. Population density rapidly increased in late May and then abruptly declined in mid-July.
Graduation date: 1991

Sphaeropsis sapinea and Diaporthe ambigua are important pathogens of forest and orchard tree species, respectively. Some isolates of S. sapinea are co-infected with two dsRNA viruses, SsRVl and SsRV2. Isolates of D. perjuncta (formerly thought to be D. ambigua) are infected with a positive-stranded RNA virus known as DaRV. While S. sapinea is. infected with a heterogeneous mixture of dsRNA elements of different sizes, D. perjuncta is infected with a single virus. This presents excellent opportunity for biocontrol of Diaporthe. The aim of this study was to assess these three viruses for possible application as biological control agents of S. sapinea and D. ambigua. This was' done by transfecting these with in vitro-produced RNA from the cloned viral genomes and assessing the pathogenicity of the transfected isolates on apples and apple trees. Attempts to transfect S. sapinea spheroplasts with SsRVl and SsRV2 failed. Co¬transfection of S. sapinea spheroplasts with both viruses also failed. Three isolates of D. ambigua and a single isolate of a Phomopsis sp. were successfully transfected with DaRV. Attempts to transfect the same fungi with a mutant of DaRV, bearing six codons for histidine immediately downsteam of an AUG thought to be a start codon for the translation of ORFl, failed. DaRV was originally thought to be isolated from D. ambigua. The fungal isolates transfected with DaRV were thought to be D. ambigua. The transfectants did not resemble the naturally-infected isolate. The ITS regions from the ribosomal DNA operon of these isolates were amplified using ITS 1 and ITS4 primer pair. The blast search revealed that the ITS sequence of the naturally-infected isolates are identical to D. perjuncta. One virus-free isolate was identified as a Phomopsis sp. while three other virus-free isolates were identified as D. ambigua. A PCR-based RFLP was developed to differentiate the naturally-infected D. perjuncta isolates from the virus¬free Phomopsis sp. and D. ambigua isolates. In the growth and pathogenicity studies, a DaRV-transfected, wild-type and negative control isolate of one Phomopsis and three D. ambigua isolates, were used. The DaR V -transfected Phomopsis sp. had a higher growth rate than the wild-type isolate. This DaRV-transfected Phomopsis sp. was more virulent on apples than the wild-type isolate. The wild-type isolate was slightly more virulent than the DaR V -transfected Phomopsis sp. on apple trees. There were no significant differences in growth rates between the DaRV-transfected and wild-type isolates of D. ambigua CMW5587 and D. ambigua CMW5287. There were no significant differences in virulence on apples between the DaRV-transfected and wild-type isolates of these fungi. The DaRV-transfected D. ambigua CMW5287 was more virulent than the wild-type isolate on apple trees. The DaRV-transfected D. ambigua CMW5587 had the same virulence as the wild-type isolate on both apples and apple trees. The DaRV-transfected D. ambigua CMW5288 had a slower growth rate than the wild-type isolate. There were no significant differences in virulence on apples between these isolates. The wild-type isolate of this isolate was significantly more virulent on apple trees than the DaRV-infected isolate. Although transfection was successfully done, the effects of DaRV on the Phomopsis sp. and D. ambigua isolates are not conclusive. In order to obtain conclusive results, virus-free isolates of D. perjuncta must be transfected. During the course of this study, there were no available virus-free isolates of this fungus.
Dissertation (PhD)--University of Pretoria, 2006.
Genetics
Unrestricted

After European settlement, Australian rangelands especially in South Australia underwent significant changes because of the main land use of pastoralism. Many studies have revealed that the plant communities are negatively effected by herbivory mainly by sheep. The main aim of this study is to separate the different effects of sheep, rabbits and kangaroos. This was examined by survey supported by experimental and modelling research. A 32,000 km² area previously surveyed by Tiver and Andrew (1997) in eastern South Australia was re-surveyed to monitor populations of perennial plant species at sites of various intensity of grazing by sheep, rabbits and kangaroos (goats populations are low in the study area), the most important vertebrate herbivores. Plant population data were collected in both sheep paddocks and historically ungrazed by sheep (road reserves) by using the Random Walk method and analyzed using Generalized Linear Modelling (GLM) to separate the effects of sheep and rabbits on plant regeneration and their regeneration in response to grazing. These data were also compared to similar data collected by Tiver and Andrew in 1992 (1997) to ascertain if the reduction in rabbit numbers through introduction of RCV had allowed increased regeneration. Regeneration of many species inside paddocks were negatively affected and species in roadside reserves neither did not significantly increase from 1992 to 2004. However, some species showed increase of populations in spite of sheep grazing, with some species being less susceptible than others. This research also indicates kangaroo grazing impact on some plant species. Reduction in rabbit numbers following the 1995 release of calicivirus has not been effective in restoring regeneration. Another experiment was conducted at Middleback Field Station near Whyalla to identify herbivore grazing pressure on the arid zone plant species Acacia aneura using unfenced, sheep fenced and rabbit fenced grazing exclosures. This experiment was set up with seedlings in exclosures, ten replicates of each treatment, at plots four different distances from the watering point to identify the survivorship of seedlings. Data were collected by recording canopy volumes of seedling over an 18 month period and analyzed by Residual Maximal Likelihood (REML). Seedlings both near and far from the watering point were severely effected by large herbivores, either sheep, kangaroos or both, and in a separate experiment kangaroo grazing effects on the seedling were also identified. Seedlings browsed by the rabbits were recovered better than the seedlings grazed by the large herbivores. Decreasing kangaroo activities has been noticed when the rabbit movements increased. Computer modelling was conducted to predict the future plant population structure over 500 years using a matrix population model developed by Tiver et al. (2006) and using data collected in the survey as a starting point. Extinction probabilities of populations of Acacia aneura near watering points, far from watering points and under pulse grazing scenarios were compared. Sheep grazing was found to cause eventual extinction of populations in all parts of sheep paddocks. Together, the results indicate that sheep are the major herbivore suppressing regeneration of perennial plant species. Kangaroo and rabbits have an identifiable but lesser effect. The results have implications for conservation and pastoral management. To achieve ecological sustainability of arid lands a land-use system including a network of reserves ungrazed by sheep and with control of both rabbit and kangaroo numbers will be required.