Letteratura scientifica selezionata sul tema "Grain Diseases and pests South Australia"

Ricefield rats (Rattus argentiventer) in south-east Asian rice fields and house mice (Mus domesticus) in Australian grain fields are major pest species. They cause damage before and after harvest and carry zoonotic diseases. For both species, management techniques have been pursued using the approach of immunocontraceptive vaccination. We review results from a series of enclosure and field studies conducted with these species to assess the effects of fertility control in small rodents. In the experiments, fertility control was simulated by tubal ligation, ovariectomy or progesterone treatment. A once-off sterilisation of 50–75% of enclosed founder females considerably reduced reproductive output of ricefield rat populations until the end of the reproductive period. In house mice, similar success was achieved when a sterility level of 67% of female founders and offspring was maintained. Repeated antifertility treatments are required because of the much longer breeding period of house mice versus ricefield rats. Comparing the results of enclosure trials with the outcome of simulation models suggests that partial compensation of treatment effects can occur through enhanced reproduction of the remaining fertile females and improved survival of juveniles. However, such compensatory effects as well as behavioural consequences of sterility in field populations are not likely to prevent the management effect at the population level. The challenge for effective fertility control of small rodents in the field is the wide-scale delivery of an antifertility treatment to founders at the beginning of the breeding season and to fertile immigrants that are recruited into the population, which otherwise contribute to the reproductive output at the population level. Future research efforts should focus on species-specific techniques and on agents that can be effectively delivered via bait.

Rainfed farms in south-eastern Australia often combine annual cropping and perennial pasture phases with grazing sheep enterprises. Such diversity serves in managing diseases, pests and plant nutrition while stabilising income in the face of wide, uncorrelated variations in international commodity prices and local weather over time. We use an actuarial accounting approach to capture the above contexts to render financial risk profiles in the form of distributions of decadal cash balances for a representative 1000-ha farm at Coolamon (34°50ʹS, 147°12ʹE) in New South Wales, Australia. For the soil and weather conditions at this location we pose the question of which approach is better when establishing the perennial pasture lucerne (Medicago sativa L.): sowing with the final crop of the cropping phase, or sowing alone following the final crop? It is less expensive to sow lucerne with the final crop, which can provide useful income from the sale of grain, but this practice can reduce pasture quantity and quality in poorer years. Although many years of field research have confirmed that sowing lucerne alone is the most reliable way to establish a pasture in this area, and years of extension messages to this effect have gone out to farmers, they often persist in sowing lucerne with their final cereal crops. For this region, counting all costs, we show that sowing lucerne alone can reduce farm financial risk (i.e. probability of negative decadal cash balances) at stocking rates >10 dry sheep equivalents (DSE)/ha, compared with the practice of sowing lucerne with a cover crop. Establishing lucerne alone allows the farmer the option to profitably run higher stocking rates for higher median decadal cash margins without additional financial risk. At low stocking rates (i.e. 5 DSE/ha), there appears to be no financial advantage of either establishment approach. We consider the level of equity, background farm debt and overhead costs to demonstrate how these also affect risk-profile positions of the two sowing options. For a farm that is deeply in debt, we cannot suggest either approach to establishing lucerne will lead to substantially better financial outcomes.

In 1991, a survey was distributed to 251 potato growers in South Australia to determine major diseases, insect and other invertebrate pests, and chemicals used to control them. The overall response rate was 48%, but of these, 24 individuals were no longer growing potatoes. The results were summarised for the State and by district (Adelaide Hills, Adelaide Plains, Murray Lands, South East). The most prevalent diseases encountered by respondents in all districts were target spot caused by Alternaria solani, and rhizoctonia canker caused by Rhizoctonia solani. Other diseases of concern to growers included late blight caused by Phytophthora infestans, seed piece decay caused by various pathogenic and saprophytic microorganisms, common scab caused by Streptomyces scabies, and leaf roll caused by potato leaf roll virus. The most commonly used fungicides for disease control were chlorothalonil (33-42% of respondents), mancozeb (30%), and cupric hydroxide (11-13%). The most commonly used seed treatments for control of seed piece decay were mancozeb (51 % of respondents), tolclofos methyl (24%), and lime (20%). Green peach aphid (Myzus persicae), potato aphid (Macrosiphum euphorbiae), potato moth (Phthorimaea operculella), and jassids and leafhoppers (Jassidae, Cicadellidae) were the pests of greatest concern to the growers. Others included Rutherglen bug (Nysius vinitor), redlegged earth mite (Halotydeus destructor), and thrips (Thripidae). The most commonly used insecticides were ethamidophos (40% of respondents), monocrotophos (22-28%), and dimethoate (7-13%).

A crop rotation trial was established in 1977 on a hard-setting red-brown earth at Tarlee, South Australia, to monitor the long-term effect of intensive and traditional rotations on soil properties and crop production. The rotations involve wheat alternating with cereals, grain legumes, pasture, and fallow. There are 3 stubble + tillage treatments: remove stubble + cultivate, retain stubble + cultivate, retain stubble + no tillage. Three rates of nitrogen (0,40, 80 kg N/ha as ammonium nitrate) are applied to the wheat. Grain yield varied with seasonal conditions, and water use efficiencies were up to 10 kg/ha. mm. In the more productive rotations, wheat grain yields expressed as a percentage of potential yield tended to increase over time. The best wheat yields were always in rotations that included a grain legume or legume pasture, with additional yield increases in all rotations coming from the use of N fertiliser. By comparison with rotation and N fertiliser effects, there was little effect of the stubble + tillage treatments on grain yield. Most of the yield variations were related to differences in tiller density or grains per ear, with grain weight remaining relatively constant over all seasons. There was a tendency for grain legume yields to decrease over the latter years of the trial, and this was attributed to the build-up of plant diseases through growing the same species on the same plot every second year. Overall, faba beans were the highest yielding grain legume, and the wheat-beans rotation, with 80 kg N/ha on the wheat, gave highest total grain production. Data for residue remaining after harvest indicate that in some years there is less than the desired minimum levels to give adequate protection against erosion, so any grazing of the residues must be carefully managed.

In grain crops, aphids are important pests, but they can be suppressed by hymenopteran parasitoids. A challenge in incorporating parasitoids into Integrated Pest Management (IPM) programs, however, is that parasitoid numbers can be low during periods within the season when aphids are most damaging. Understanding the population dynamics of key aphid species and their parasitoids is central to ameliorating this problem. To examine the composition and seasonal trends of both aphid and parasitoid populations in south-eastern Australia, samples were taken throughout the winter growing seasons of 2017 and 2018 in 28 fields of wheat and canola. Myzus persicae (Sulzer) was the most abundant aphid species, particularly within canola crops. Across all fields, aphid populations remained relatively low during the early stages of crop growth and increased as the season progressed. Seasonal patterns were consistent across sites, due to climate, crop growth stage, and interactions between these factors. For canola, field edges did not appear to act as reservoirs for either aphids or parasitoids, as there was little overlap in the community composition of either, but for wheat there was much similarity. This is likely due to the presence of similar host plants within field edges and the neighbouring crop, enabling the same aphid species to persist within both areas. Diaeretiella rapae (M’Intosh) was the most common parasitoid across our study, particularly in canola, yet was present only in low abundance at field edges. The most common parasitoid in wheat fields was Aphidius matricariae (Haliday), with field edges likely acting as a reservoir for this species. Secondary parasitoid numbers were consistently low across our study. Differences in parasitoid species composition are discussed in relation to crop type, inter-field variation, and aphid host. The results highlight potential focal management areas and parasitoids that could help control aphid pests within grain crops.

In grain crops, aphids are important pests, but they can be suppressed by hymenopteran parasitoids. A challenge in incorporating parasitoids into Integrated Pest Management (IPM) programs, however, is that parasitoid numbers can be low during periods within the season when aphids are most damaging. Understanding the population dynamics of key aphid species and their parasitoids is central to ameliorating this problem. To examine the composition and seasonal trends of both aphid and parasitoid populations in south-eastern Australia, samples were taken throughout the winter growing seasons of 2017 and 2018 in 28 fields of wheat and canola. Myzus persicae (Sulzer) was the most abundant aphid species, particularly within canola crops. Across all fields, aphid populations remained relatively low during the early stages of crop growth and increased as the season progressed. Seasonal patterns were consistent across sites, due to climate, crop growth stage, and interactions between these factors. For canola, field edges did not appear to act as reservoirs for either aphids or parasitoids, as there was little overlap in the community composition of either, but for wheat there was much similarity. This is likely due to the presence of similar host plants within field edges and the neighbouring crop, enabling the same aphid species to persist within both areas. Diaeretiella rapae (M’Intosh) was the most common parasitoid across our study, particularly in canola, yet was present only in low abundance at field edges. The most common parasitoid in wheat fields was Aphidius matricariae (Haliday), with field edges likely acting as a reservoir for this species. Secondary parasitoid numbers were consistently low across our study. Differences in parasitoid species composition are discussed in relation to crop type, inter-field variation, and aphid host. The results highlight potential focal management areas and parasitoids that could help control aphid pests within grain crops.

The lesser grain borer, Rhyzopertha dominica, and the rust red flour beetle, Tribolium castaneum, are two major beetle pests commonly found infesting stored products worldwide. Both species can cause severe economic damage and their management is complicated by their potential to develop resistance to several of the limited chemical options available. However, pest management strategies can be improved by understanding the ecology of the pest insect. To determine the spatiotemporal activity of R. dominica and T. castaneum, we conducted a trapping study over two years in a temperate region of south-eastern Australia, with traps located near grain storages and fields. We captured higher numbers of R. dominica than T. castaneum, and both species were more prevalent in traps located close to grain storages. Similar and consistent seasonal patterns were displayed by both species with activity ceasing during the winter (June–August) months. We found linear correlations between maximum daily temperatures and trap catches, and minimum threshold temperatures for flight activity were 14.5 °C and 15.6 °C for R. dominica and T. castaneum, respectively. The results are discussed in relation to the ecology of these pests along with their implications for pest management.

European rabbits are exotic pests in Australia, New Zealand, parts of South America and Europe, and on many islands. Their abundance, and the damage they cause, might be reduced by the release of naturally occurring or genetically modified organisms (GMOs) that act as biological control agents (BCAs). Some promising pathogens and parasites of European rabbits and other lagomorphs are discussed, with special reference to those absent from Australia as an example of the range of necessary considerations in any given case. The possibility of introducing these already-known BCAs into areas where rabbits are pests warrants further investigation. The most cost-effective method for finding potentially useful but as-yet undiscovered BCAs would be to maintain a global watch on new diseases and pathologies in domestic rabbits. The absence of wild European rabbits from climatically suitable parts of North and South America and southern Africa may indicate the presence there of useful BCAs, although other explanations for their absence are possible. Until the non-target risks of deploying disseminating GMOs to control rabbits have been satisfactorily minimised, efforts to introduce BCAs into exotic rabbit populations should focus on naturally occurring organisms. The development of safe disseminating GMOs remains an important long-term goal, with the possible use of homing endonuclease genes warranting further investigation.

Fungicides and insecticides used at the recommended rate, and reduced recommended rates were applied at low volume (100 L ha-1) to apple trees in field experiments in South Australia from 1985 to 1988. At harvest the incidence of fruit damaged by fungi and insects was assessed on Golden Delicious, Red Delicious, Jonathan and Granny Smith cultivars. Mixtures of penconazole and mancozeb applied at the recommended rates of 800 mL and 4.5 kg ha-1 respectively as well as 25% and 10% of the recommended rates controlled apple scab completely in 1986, but were less effective in 1987. Azinphos-methyl applied at the recommended rate of 2.7 kg and 25% of the recommended rate reduced codling moth infestation to commercially acceptable levels of <2 % on Red Delicious only in 1987. Considerable cost savings are possible by using low rates of pesticides. Our results suggest that the use of low rates is more applicable to low valued cultivars such as Jonathans and orchards with low levels of pest and disease.

Austropuccinia psidii (myrtle rust) is a globally invasive neotropical rust of the Myrtaceae that came into international prominence following extensive damage to exotic Eucalyptus plantations in Brazil in the 1970s and 1980s. In 2005, myrtle rust established in Hawaii (USA), and over the past 12 years has spread from the Americas into Asia, the Pacific, and South Africa. Myrtle rust was detected in Australia in 2010, and the response and ultimately unsuccessful eradication attempt was a lesson to those concerned about the threat of exotic pests and diseases to Australia's environment. Seven years following establishment, we are already observing the decline of many myrtaceous species and severe impacts to native plant communities. However, the recently developed Myrtle rust in Australia draft action plan identified that there is no nationally coordinated response strategy for the environmental dimensions of this threat. Recent reviews have identified a greater need for involvement from environmental agencies in biosecurity preparedness, response, and resourcing, and we believe this approach needs to extend to the management of invasive environmental pathogens once they establish.

Bibliography: leaves 81-100. Entry of inoculum into a crop and disease development in the crop cannot be prevented because spores are airborne and there is a lack of highly resistant varieties. This makes complete control of chocolate spot unlikely. It should however, be possible to improve current levels of disease control through the integration of the factors identified in the study.

Three pages of addenda pasted inside back cover. Bibliography: leaves 166-189. Rhizoctonia solani is a complex species comprising morphologically basidiomycetous imperfect fungi. This study aimed to determine genetic diversity within R. solani AG-3 causing rhizoctonia disease of potato in South Australia. For this purpose, pectic zymogram, PCR, DNA fingerprinting and RFLP techniques were used in conjunction with traditional plant pathology procedures.

Bibliography: leaves 224-236. The study aimed to determine the distribution of both P. thornei and P. neglectus in South Australia. Also to study the field and laboratory population dynamics of P. thornei in relation to wheat yields, to determine its host range on a variety of cereal and non-leguminous hosts and to identify possible sources of nematode resistant wheat cultivars/varieties. Preliminary experiments studied the involvement of root rotting fungi with the nematode in wheat disease.

Bibliography: leaves 307-329. This study concludes that in soils in South Australia where root-rotting fungi and P. neglectus exist together, root disease of wheat is caused by their combined effect. Evidence suggests that P. neglectus not only contributes to this interaction through mechanical wounding of roots, but also causes biochemical and physiological changes in plants, making them more prone to fungal infection.

Bibliography: leaves 131-153. This thesis investigates the mechanisms of manganese (Mn) efficiency (genetic tolerance to Mn-deficient soils) in barley (Hordeum vulgare L.) at both physiological and molecular levels.

Thesis (MScAgric)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: The grain chinch bug, Macchiademus diplopterus, is an endemic pest of cultivated grain crops and wild grasses in the south-western Cape region of South Africa. In early summer when host plants dry out, adult grain chinch bugs aggregate in large numbers in shelter sites in surrounding areas and enter into aestivation. These shelter sites sometimes include the stalk or calyx ends of fruit, and shelter-seeking bugs can also contaminate export fruit cartons, consequently posing a phytosanitary/quarantine risk to importing countries. Presently, there are no feasible pre- or post-harvest control measures to manage this quarantine risk. The aggregating behaviour of grain chinch bugs suggests the involvement of pheromones. Therefore, investigating the chemical ecology of grain chinch bugs for potential use in control measures is the focus of the first research chapter of this study. Gas chromatography-mass spectrometry (GC-MS) was used to identify headspace volatiles collected from aggregating bugs. Olfactometer bioassays were conducted to assess the attractiveness of each gender to separate sexes, individual compounds and a mixture of the compounds as a formulated lure. The lure was tested in field trapping trials with delta and bucket traps. In the bioassays with the live insects the response of each gender to live females was greater than the responses of each gender to live males, suggesting that females may disseminate the pheromones more efficiently than males. The following eight volatile compounds were indentified from the GC-MS analysis: hexanal, (E)-2-hexenal, (E)-2-hexenol, (E)-2-hexenyl acetate, (E)-2-octenal, (E)-2-octenol, (E)-2-octenyl acetate and tridecane. In the bioassays with individual compounds, three of these eight compounds, hexanal, (E)-2-hexenal, and tridecane, elicited attraction of both females and males. The formulated lure was attractive to both males and females in the laboratory bioassay, but this attraction was not evident in the field. In the field, there was only one occasion when a significantly higher number of bugs were caught in baited traps compared to unbaited traps. Trap catches were very low compared to the actual level of infestation in the field which was evident from corrugated cardboard bands tied around tree trunks which contained many sheltering bugs. The low trap catches seen in the field were partly due to competition between the synthetic pheromone lure and the natural pheromones emitted by aggregating live insects. Also, the characteristic shelter-seeking behaviour of grain chinch bugs influenced trap catches, as more bugs were found in places that provide shelter, like cardboard bands and walls of the delta traps. This behavior of aestivating bugs could be used to the advantage of trapping bugs by integrating sheltering sites into traps in future trials. Also, the lure needs to be improved for optimum efficiency in the field. The second research chapter also addresses the quarantine risk posed by grain chinch bugs, by investigating the thermal biology of bugs to ultimately facilitate the development of effective post-harvest treatments. Critical thermal minimum and maximum temperatures (CTmin and CTmax) of both active and aestivating bugs were subjected to critical thermal limits analysis. The CTmin and CTmax of aestivating bugs were not affected by gender (p > 0.05). There was a decrease in CTmin from the active period into aestivation for both males (2.8°C to 1.0°C (± 0.1)) and females (2.1°C to 0.6°C (± 0.1)). Also, for CTmax there was an increase in tolerance from the active period into the aestivation period for both males (49.9°C to 51.0°C (± 0.1)) and females (49.9°C to 51.5°C (± 0.1)). To determine the plasticity of grain chinch bug thermal tolerance, aestivating bugs at 27 weeks into aestivation, were acclimated at different temperatures and photoperiods [18°C (10L:14D) and 26°C (16L:8D)] for a period of seven days. Both low (18°C) and high (26°C) acclimation temperatures and photoperiods increased CTmin of aestivating grain chinch bugs at 14 weeks from 0.8°C to -1.2°C and -0.1°C (± 0.1) respectively. However, CTmax was not altered by acclimation temperatures (p > 0.82). Field temperatures at collection sites were recorded to compare to grain chinch bugs thermal tolerance levels exhibited in the laboratory. These results, as well as the effects of acclimation treatments on the CTmin of bugs, have implications for post-harvest treatments, and understanding the quarantine risk posed to importing countries. The information generated from this study can be used to further advance the development of both effective pre-harvest and post-harvest control measures to reduce grain chinch bug quarantine risk.
AFRIKAANSE OPSOMMING: Die graanstinkluis, Macchiademus diplopterus, is 'n endemiese plaag van aangeplante graangewasse en wilde grasse in die Suidwes Kaap-provinsie van Suid-Afrika. In die vroeë somer wanneer gasheerplante uitdroog, soek groot getalle volwasse graanstinkluise skuiling in die omliggende gebiede en gaan in ʼn somerrusperiode. Hierdie skuilplekke sluit soms die stam of kelk eindes van vrugte in en graanstinkluise kan ook uitvoer-vrugte kartonne kontamineer. Gevolglik word lande wat vrugte uit Suid-Afrika invoer, aan die fitosanitêre kwarantynrisiko van stinkluisbesmetting blootgestel. Tans is daar nie haalbare voor- of na-oes beheermaatreëls om hierdie kwarantyn risiko te bestuur nie. Die aggregasiegedrag van graanstinkluise dui op die betrokkenheid van ʼn feromoon. ‘n Ondersoek van die chemiese ekologie van die graanstinkluis vir moontlike gebruik in beheermaatreëls is die fokus van die eerste gedeelte van hierdie studie. Gaschromatografie-massaspektrometrie (GC-MS) is gebruik om die vlugtige organiese verbindings in die bodamp van die saamgetrosde stinkluise te identifiseer. Olfaktometriese biotoetse is uitgevoer om die aantreklikheid van die insekte vir die teenoorgestelde geslag te bepaal, asook van die individuele verbindings en 'n mengsel van die verbindings as 'n geformuleerde lokmiddel in lokvalle. Die lokmiddel is getoets in veldproewe met deltatipe en emmertipe lokvalle. In die olfaktometriese biotoetse met die lewende insekte is die reaksie van beide geslagte teenoor lewende wyfies groter as die reaksie van die geslagte teenoor mannetjies, wat daarop dui dat wyfies die feromoon meer doeltreffend as mannetjies versprei. Die volgende agt verbindings is geïdentifiseer met behulp van GC-MS-analise: heksanaal, (E)-2-heksenaal, (E)-2-heksenol, (E)-2-heksenielasetaat, (E)-2-oktenaal, (E)-2-oktenol, (E)-2-oktenielasetaat en tridekaan. In die biotoetse met individuele verbindings het drie van die agt verbindings, hexanal, (E)-2-hexenal, en tridecane, lokaktiwiteit vir beide geslagte getoon. Die geformuleerde lokmiddel was aantreklik vir beide geslagte in laboratorium toetse, maar soortgelyke lok is nie in die veld gevind nie, waar daar net een keer 'n aansienlike groter getal graanstinkluise met lokmiddel gevang is in vergelyking met lokvalle sonder lokmiddel. Die getal graanstinkluise in lokvalle was baie laag in vergelyking met die werklike vlak van besmetting in die veld, wat duidelik geblyk het uit die getalle graanstinkluise wat skuiling gesoek het in die geriffelde karton bande wat om boomstamme vasgemaak was. Die lae lokvalvangste in die veld was deels te wyte aan die kompetisie tussen sintetiese feromoon en die natuurlike feromoon van saamgetrosde insekte. Die kenmerkende aggregasiegedrag van graanstinkluise het lokvalvangste beïnvloed, aangesien meer stinkluise gevind is in plekke wat skuiling bied, soos die kartonbande en die binnekant van die delta-lokvalle. Hierdie skuilings van graanstinkluise kan in toekomstige proewe uitgebuit word deur vir meer skuilplek in lokvalle voorsiening te maak. Die formulering en die aanbieding van die lokmiddle moet ook verbeter word vir 'n optimale doeltreffendheid in die veld. In die tweede hoofstuk word die kwarantynrisiko van die graanstinkluis aangespreek deur die ondersoek van die termiese biologie van stinkluise om uiteindelik die ontwikkeling van doeltreffende na-oes behandelings te fasiliteer. Kritiese termiese minimum en maksimum temperature (CTmin en CTmax) van beide aktiewe en rustende graanstinkluise is bepaal deur analise van die kritiese termiese beperkings van die insek. Die CTmin en CTmax van rustende graanstinkluise is nie geraak deur geslag nie (p > 0.05). Daar was 'n afname in CTmin van die aktiewe tydperk tot in rus, vir beide manlike (2.8°C tot 1.0°C (± 0.1)) en vroulike insekte (2.1°C tot 0.6°C (± 0.1)). Ook vir die CTmax was daar 'n verbetering in toleransie vanaf die aktiewe tydperk tot in die rusperiode vir beide manlike (49.9°C tot 51.0°C (± 0.1)) en vroulike insekte (49.9°C tot 51.5°C (± 0.1)). Om die aanpasbaarheid van die termiese toleransie van die graanstinkluis te bepaal, is graanstinkluise 27 weke na aanvang van die rusperiode geakklimatiseer by verskillende temperature en fotoperiodes [18°C (10L: 14D) en 26°C (16L: 8D)] vir 'n tydperk van sewe dae. Beide lae (18°C) en hoë (26°C) akklimatiseringstemperature en fotoperiodes het onderskeidelik die CTmin van rustende graanstinkluise op 14 weke verhoog van 0.8°C tot -1.2°C en -0.1°C (± 0.1). Daar is egter geen effek op CTmax deur akklimasie temperature nie (p > 0.82). Veldtemperature is ook bepaal om te vergelyk met graanstinkluis termiese toleransie vlakke wat in die laboratorium bepaal is. Hierdie resultate, sowel as die gevolge van die akklimasie behandelings op die CTmin van graanstinkluise, het implikasies vir na-oes behandelings, en begrip van die kwarantyngevaar wat dit inhou vir vrugte-invoerlande. Die inligting wat uit hierdie studie voortvloei, kan gebruik word om die ontwikkeling van beide effektiewe voor-oes en na-oes beheermaatreëls te bevorder en om die kwarantynrisiko wat graanstinkluise inhou, te verminder.