Dissertations / Theses on the topic 'Plant diseases Epidemiology'

Thesis (MScAgric)--University of Stellenbosch, 2002.
ENGLISH ABSTRACT: Historically root diseases have been a production-limiting problem for the strawberry industry worldwide. In the Western Cape Province of South Africa the most serious root disease is black root rot, which causes losses of up to 30%, annually. The aims of this study were to investigate aspects of the etiology and epidemiology of this disease in the Western Cape, and to provide information that can be incorporated in an integrated disease management strategy. In Chapter I a summary of published information on this disease is presented. Disease symptoms include severe stunting of plants, which have black, rotted, reduced root systems. Even though this disease is of great economic importance, the etiology remains unresolved. However, soilborne fungal root pathogens, particularly Pythium and Rhizoctonia spp. have been implicated as major role players. Control of this disease, as well as the other root diseases affecting strawberries, has relied on soil fumigation with broad spectrum chemical fumigants, in particular methyl bromide. However, due to the ozone depleting action of methyl bromide it was decided at the signing of the Montreal Protocol to remove this chemical from the market. This action has caused great demand for alternative measures to control root diseases on many crops including strawberries. Development of integrated disease management strategies is dependent upon a more complete understanding of the etiology, biology and ecology of the disease complex. In Chapter 2 fungal pathogens associated with diseased plants were isolated and Koch's postulates were carried out. The most frequently isolated fungal pathogens were Pythium irregulare, Rhizoctonia spp. and Cylindrocarpon destructans. Two morphotypes of Rhizoctonia were isolated viz. a brown and a white type. Pythium irregulare was isolated more frequently in July than in September, and was not isolated at all in November. Rhizoctonia spp. were present at all sampling dates but were more frequently isolated in November than at the other times. All the fungi that were tested were pathogenic and caused root lesions. Cylindrocarpon destructans and Coniella fragariae did not have a stunting effect on the plants. These results confirm a major role for Pythium and Rhizoctonia in the black root rot complex and suggest that there is a complimentary seasonal variation in occurrence between these two pathogens. The Rhizoctonia species and anastomosis groups of isolates obtained from diseased strawberries in the Western Cape Province were determined, and their pathogenicity and relative virulence assessed. Both binucleate and multinucleate types were recovered from diseased roots and identified as R. fragariae and R. so/ani, respectively. All isolates of R. solani were members of anastomosis group (AG) 6, whereas three AG types were identified among isolates of R. fragariae, viz. AG-A, AG-G and AG-I at a relative occurrence of 69%, 25%, 6% respectively. All Rhizoctonia isolates were pathogenic to strawberry, but R. solani (AG 6) was the most virulent causing severe stunting of plants. This is the first species confirmation and AG type identification of Rhizoctonia taxa causing root rot of strawberries in South Africa. An assessment of the presence and quantity of black root rot pathogens associated with soils prior to fumigation and post fumigation with methyl bromide, was made in Chapter 4. Isolations were also made from nursery plants to determine whether any black root rot pathogens were in the plants before transplanting. Results demonstrated that after fumigation the soil was free of all pathogenic fungi associated with the disease. However, the main pathogens involved in black root rot, viz. Rhizoctonia fragariae, R. solani and Pythium spp. were isolated from nursery plants. The fact that the plants are already infected with these pathogens renders the prospects for control of this disease difficult. Further studies are urgently required to develop production practices that can be included in disease management programmes. In vitro studies were carried out to determine the ECso values of different fungicides for isolates of Pythium irregulare, Rhizoctonia fragariae AG-A, AG-G and AG-I and R. solani AG 6. Benomyl, fludioxonil and tolc1ofos-methyl were used in these tests. Field trials were also conducted using these fungicides. In Chapter 5 it is shown that in general application of fungicides improved the yield and did not affect the survival rate of strawberry plants. Fludioxonil showed potential for short-term use. Applications of fungicides that targeted specific fungal genera were not sufficient to control the disease. Seasonal fluctuation of Pythium and Rhizoctonia spp. became apparent with the occurrence of Pythium being relatively high early in the season but low late in the season. Conversely, the occurrence of Rhizoctonia was low at the beginning of the season but high late in the season. In the short-term there is potential for fungicide applications as part of an integrated disease management strategy, but the economic feasibility of this practice needs to be assessed. In this study the major pathogens causing black root rot were identified in the Western Cape Province of South Africa, and important information regarding the epidemiology of the disease was reported. These results can be incorporated in an integrated management strategy to reduce losses of strawberry production, attJibutable to black root rot.
AFRIKAANSE OPSOMMING: Wortelsiektes is wêreldwyd 'n produksie-beperkende probleem vir die aarbeibedryf. . Swartwortelvrot, wat jaarliks verliese van tot 30% veroorsaak, is die belangrikste wortelsiekte in die Wes-Kaap Provinsie van Suid-Afrika. Die doelwitte van hierdie studie was om aspekte van die etiologie en epidemiologie van die siekte in die Wes- Kaap te ondersoek en inligting wat in geïntegreerde siektebestuurstrategië ingesluit kan word, te voorsien. In Hoofstuk 1 word 'n opsomming van gepubliseerde inligting aangaande die siekte uiteengesit. Siektesimptome sluit ernstige verdwerging van plante met swart verotte en verkleinde wortelstelsels in. Alhoewel die siekte van groot ekonomiese belang is, is die etiologie grootliks onbekend. Grondgedraagde wortelpatogene swamme, spesifiek Pythium en Rhizoctonia spp., is egter as belangrike rolspelers geïdentifiseer. Tot dusver het die beheer van hierdie siekte sowel as ander wortelsiektes van aarbeie berus op grondberoking met breë spektrum chemiese berokingsmiddels, spesifiek metielbromied. As gevolg van die osoonafbrekende aksie van metielbromied is daar egter tydens die ondertekening van die Montreal Protocol besluit om dié middel van die mark te verwyder. Hierdie besluit het 'n groot aanvraag na alternatiewe beheermaatreëls vir wortelsiektes van verskeie gewasse, insluitende aarbeie, veroorsaak. Die ontwikkeling van geïntegreerd siektebestuurstrategieë is egter afhanklik van 'n meer volledige begrip van die etiologie, biologie en ekologie van die siektekompleks. In Hoofstuk 2 is die patogene swamme wat met die siekte geassosieer word, geïsoleer, en is Koch se postulate uitgevoer. Die mees algemeen geïsoleerde patogene swamme was Pythium irregulare, Rhizoctonia spp. en Cylindrocarpon destructans. Twee morfotipes van Rhizoctonia is geïsoleer, nl. 'n bruin tipe en 'n wit tipe. Pythium irregulare is meer dikwels in Julie as in September geïsoleer, maar glad nie in November nie. Rhizoetonia het tydens alle monstertye voorgekom, maar is meer dikwels in November geïsoleer. Al die swamme wat getoets is, was patogenies en het letsels op die wortels veroorsaak. Cylindroearpon des true tans en Coniella fragariae het nie'n verdwergingseffek op plante gehad nie. Hierdie resultate bevestig die dominante rol van Pythium en Rhizoctonia in die swartwortelvrot kompleks en dui op 'n komplementêre seisoenale variasie in die voorkoms van hierdie twee patogene. Die Rhizoctonia spesies en anastomose groepe (AG) van die isolate geisoleer vanaf siek aarbeiplante in die Wes-Kaap Provinsie is bepaal, en die patogenisiteit en relatiewe virulensie is beraam. Sowel tweekernige as multikernige tipes is vanaf siek wortels geïsoleer en respektiewelik as R. fragariae en R. so/ani geïdentifiseer. Alle isolate van R. so/ani was lede van anastomose groep 6, terwyl drie AG tipes, nl. AGA, AG-G en AG-I onder die R. fragariae isolate geïdentifiseer is met relatiewe voorkomste van 69%, 25%, 6% respektiewelik. Alle Rhizoctonia isolate was patogenies op aarbeie, maar R. so/ani (AG 6) was die mees virulente en het ernstige verdwerging van plante veroorsaak. Hierdie is die eerste bevestiging van spesies en identifisering van AG tipes van Rhizoctonia taksa wat wortelvrot van aarbeie in Suid Afrika veroorsaak. In Hoofstuk 4 is 'n beraming van die voorkoms en hoeveelheid swartwortelvrot patogene geassosieer met grond voor, en na beroking met metielbromied, gemaak. Isolasies is ook vanaf kwekeryplante gemaak om te bepaal of enige swartwortelvrot patogene voor oorplanting in die plante teenwoordig was. Die resultate het getoon dat grond na beroking vry was van alle patogeniese swamme geassosieër met die siekte. Die hoof patogene betrokke in die swartwortelvrot kompleks, nl. Rhizoctonia fragariae, R. so/ani en Pythium spp. was egter in die kwekery plante teenwoordig. Die feit dat plante reeds met hierdie patogene geïnfekteer is, maak die vooruitsigte vir die beheer van hierdie siekte moeilik. Verdere studies word dringend benodig vir die ontwikkeling van produksiepraktyke wat by siektebestuursprogramme ingesluit kan word. In vitro studies om die ECso waardes van die isolate van Pythium irregulare, Rhizoctonia fragariae AG-A, AG-G en AG-I en R. so/ani AG 6 vir die fungisiedes benomyl, fludioxonil en tolclofos-metiel te bepaal, is uitgevoer. Hierdie fungisiedes is ook in veldproewe getoets. In Hoofstuk 5 is getoon dat aanwending van fungisiedes die opbrengs verbeter het en nie die oorlewing van aarbeiplante beïnvloed het nie. Fludioxonil het potensiaal vir korttermyn gebruik getoon. Die aanwending van fungisiedes wat spesifieke swamgenera teiken, was nie voldoende om die siekte te beheer nie. Seisoenale fluktuasies van Pythium en Rhizoctonia spp. het duidelik geword met die relatief hoë voorkoms van Pythium vroeg in die seisoen, maar lae voorkoms laat in die seisoen, terwyl die voorkoms van Rhizoctonia laag was aan die begin van die seisoen, maar hoog later in die seisoen. In die korttermyn is daar potensiaal vir fungisiedtoedienings as deel van 'n geïntegreerde siektebestuurstrategie, maar die ekonomiese haalbaarheid van hierdie praktyk moet bepaal word. In hierdie studie is die hoof patogene wat swartwortelvrot van aarbeie in die Wes-Kaap Provinsie van Suid-Afrika veroorsaak geïdentifiseer, en belangrike inligting rakende die epidemiologie van die siekte is aangeteken. Hierdie resultate kan in 'n geïntegreerde bestuurstrategie geïnkorporeer word om verliese van aarbeiproduksie, toeskryfbaar aan swartwortelvrot te, verminder.

Thesis (MScAgric)--University of Stellenbosch, 2005.
ENGLISH ABSTRACT: Fruit and Leaf Spot Disease (FLSD) of citrus, caused by Phaeoramularia angolensis, is found only in 18 countries in Africa, the Comores Islands in the Indian Ocean and Yemen in the Arabian peninsula. The major citrus export countries in Africa are Morocco, South Africa, Swaziland, and Zimbabwe. Zimbabwe is the only country affected by FLSD. FLSD is a disease of major phytosanitary and economic importance and its devastating effect on citrus is highlighted by the fact that the damage is cosmetic, which renders the fruit unmarketable. Total crop losses are not uncommon in Kenya. The aims of the present study, therefore, was was to determine the occurrence of P. angolensis in Zimbabwe and neighbouring Mozambique, to compare these isolates with the Cercospora Fresen. isolates from Swaziland and South Africa, to determine the epidemiology of the pathogen and to implement an effective control strategy to prevent the spread of FLSD. Leaf samples with citrus canker-like lesions collected in the early 1990’s in Zimbabwe were found to be infected by the fungus, Phaeoramularia angolensis. Surveys were undertaken to determine the spread and intensity of FLSD in Zimbabwe and Mozambique. In Zimbabwe, P. angolensis was limited to an area above the 19° south latitude, predominantly the moist areas and not the low-lying drier parts of the country. In Mozambique, no P. angolensis symptoms were found. Observations during the survey indicated that no proper management systems were implemented by Zimbabwean growers. A cercosporoid fungus causing a new Fruit and Leaf Spot Disease on Citrus in South Africa was identified. From morphological and rDNA sequence data (ITS 1, 5.8S and ITS 2), it was concluded that the new disease was caused by Cercospora penzigii, belonging to the Cercospora apii species complex. The genera Pseudophaeoramularia and Phaeoramularia are regarded as synonyms of Pseudocercospora, and subsequently a new combination was proposed in Pseudocercospora as P. angolensis. Cercospora gigantea was shown to not represent a species of Cercospora, while Mycosphaerella citri was found to be morphologically variable, suggesting that it could represent more than one taxon. A control strategy for the control of FLSD was evaluated in the study. The data showed that P. angolensis in Zimbabwe can be managed successfully by the removal of all old and neglected orchards, and on timely fungicide applications. Trifloxystrobin + mancozeb + mineral spray oil (20 g + 200 g + 500 ml/100 l water) applied in November, January and March was the most effective treatment. Three applications of benomyl + mancozeb + mineral spray oil (25 g + 200 g + 500 ml/100 l water) applied during the same period, was the second most effective treatment, and two applications (November and January) of trifloxystrobin + mineral spray oil (20g + 500 ml/100 l water) and difenoconazole (40 g) per 100 l/water applied twice in November and January, the third most effective treatment. The spore trap and weather data showed that P. angolensis needs high moisture and temperatures in excess of 25°C for disease development. It is concluded that P. angolensis in Zimbabwe can be managed successfully by implementing a holistic approach, which should be supported by the authorities, organised agriculture and all technical personnel involved in citrus production.
AFRIKAANSE OPSOMMING: Blaar- en vrugvleksiekte (BVVS) op sitrus, veroorsaak deur Phaeoramularia angolensis, kom in 18 lande in Afrika voor asook die Comores Eilande in die Indiese Oseaan en Yemen op die Arabiese skiereiland. Marokko, Suid Afrika, Swaziland en Zimbabwe is die belangrikste uitvoerders van sitrus in Afrika. Van dié lande het slegs Zimbabwe blaar en vrugvleksiekte op sitrus. Hierdie siekte is van fitosanitêre en ekonomiese waarde en die nadelige effek van die siekte, wat slegs kosmetiese van aard is, is venietigend aangesien vrugte onbemarkbaar is. Totale opbrengsverliese is nie ongewoon in lande soos Kenya nie. Die doelwitte van die studie was dus om die voorkoms van P. angolensis in Zimbabwe te bepaal, om die Cercospora Fresen. isolate vanaf Swaziland en Suid-Afrika met mekaar te vergelyk, om die epidemiologie van die siekte vas te stel en om ‘n effektiewe beheermaatreël teen die siekte te ondersoek. Blaarmonsters met kankeragtige letsels wat in die vroeë 1990’s in Zimbabwe gevind is, het getoon dat die blare geinfekteer is met die swam, Phaeoramularia angolensis. Ondersoeke is geloots om die verspreiding en intensiteit van BVVS in Zimbabwe en Mosambiek te bepaal. In Zimbabwe was gevind dat P. angolensis beperk was tot gebiede bo die 19° Suid breedtegraad, wat die hoër vogtiger gebiede insluit eerder as die droeër, laagliggende gebiede. Geen P. angolensis simptome kon in Mosambiek gevind word nie. Tydens die opnames was dit duidelik dat geen geskikte beheerstrategieë toegepas word deur Zimbabwe se produsente nie. ‘n Nuwe cercosporoid swam, wat blaar en vrugvleksiekte op sitrus is in Suid Afrika veroorsaak is geidentifiseer. Morfologiese en rDNA volgorde (ITS 1, 5.8S en ITS 2) data het getoon dat die siekte veroorsaak word deur Cercospora penzigii wat tot die Cercospora apii spesie kompleks behoort. Die genus Pseudophaeoramularia kan as sinoniem van Pseudocercospora beskou word en ‘n nuwe kombinasie word voorgestel in Pseudocercospora as P. angolensis. Cercospora gigantea het getoon dat dit nie ‘n spesie van Cercospora kon verteenwoordig nie terwyl Mycosphaerella citri varieërend voorkom en meer as een takson kan verteenwoordig. ‘n Beheerstrategie vir die beheer van BVVS is ondersoek. Die data wys dat P. angolensis in Zimbabwe doeltreffend beheer kan word deur die uitroeiing van ou en verwaarloosde bome, en deur goed beplande fungisied bespuiting. Trifloxystrobin + mancozeb + minerale spuitolie (20 g + 200 g + 500 ml/100 l water), wat in November, Januarie en Maart toegedien is, was die mees effektiefste behandeling. Drie bespuitings van benomyl + mancozeb + minerale spuitolie (25 g + 200 g + 500 ml/100 l water) wat oor dieselfde tydperk toegedien is, was die naas beste behandeling. Trifloxystrobin (20 g) + minerale spuitolie (500 ml) per 100 l/water en difenoconazole (40 g) per 100 l/water, beide as twee bespuitings toegedien in November en Januarie, het die derde beste resultaat opgelewer. Die spoorlokval en klimatologiese data het getoon dat P. angolensis vogtige toestande en temperature hoër as 25°C benodig vir siekteontwikkeling. Die afleiding uit die studie is dat P. angolensis suksesvol beheer kan word indien ‘n holistiese benadering gevolg word en alle rolspelers naamlik die owerheid, georganiseerde landbou en tegniese personeel die proses ondersteun.

Frente à recente detecção em território brasileiro de Monilina laxa, que assim como M. fructicola, é causadora da podridão parda do pessegueiro, e à falta de informações sobre a epidemiologia dos patógenos causadores da doença em regiões subtropicais, surgiu a necessidade deste trabalho, que teve por objetivos determinar as melhores condições de temperatura e molhamento para o desenvolvimento de M. fructicola e M. laxa in vitro e para a infecção e colonização pêssegos por conídios dos patógenos. Quatro isolados de M. fructicola e um isolado de M. laxa, provenientes de plantios do Estado de São Paulo e mantidos no laboratório de Epidemiologia da ESALQ, foram estudados. Foram avaliados os efeitos da temperatura e da duração do molhamento na germinação dos conídios in vitro e o efeito da temperatura no crescimento micelial e na esporulação dos patógenos. Ensaios para determinar a sensibilidade dos patógenos ao fungicida iminoctadina também foram conduzidos. Adicionalmente, pêssegos maduros foram adquiridos, feridos, inoculados com suspensão de conídios e incubados em diferentes temperaturas sob diferentes períodos de câmara úmida. Diariamente incidência e severidade foram avaliadas. A esporulação foi avaliada ao final de cada tratamento. A faixa ótima de temperatura para germinação de conídios de M. laxa, de 5 a 30ºC, é maior que a de M. fructicola, de 10 a 30ºC. O período de molhamento não teve influência na germinação dos conídios. A melhor faixa de temperatura para crescimento micelial tanto de M. fructicola quanto M. laxa de foi de 20 a 25ºC. A esporulação de M. laxa foi inversamente proporcional à temperatura de incubação. Não houve relação entre temperatura e produção de esporos em M. fructicola. Ambas as espécies mostraram-se sensíveis, in vitro, à molécula iminoctadina. A incidência da podridão parda foi superior a 80,9% em todos os tratamentos, para as duas espécies fúngicas. A 10ºC os períodos de incubação e de latência foram menores para M. laxa que para M. fructicola. A faixa ótima de temperatura para o desenvolvimento de lesões variou de 15 a 25ºC para os dois patógenos. A esporulação dos patógenos não mostrou relação com a temperatura nos ensaios in vivo. Diferenças nos sinais da espécie do patógeno foram observados nas lesões.
Due to the recent detection in Brazil of Monilinia laxa, that similar to M. fructicola causes the brown rot of peaches, and the lack of information about the epidemiology of the causal agents of this disease from subtropical regions, raised the need of such a study, which the aims were to determine the best temperature and wetness duration conditions to the development of M. fructicola and M. laxa in vitro and to infection and colonization of peaches by conidia from both pathogens. Four M. fructicola isolates and one M. laxa isolate, collected from infected fruit of São Paulo orchards and maintained at the Epidemiology Laboratory at ESALQ, were studied. Temperature and wetness duration effects on conidia germination in vitro and temperature effects on mycelial growth and sporulation of pathogens were evaluated. Trials to evaluate the sensitivity of isolates to the fungicide iminoctadine were also conducted. Furthermore, mature peaches were wounded on the surface, inoculated with a conidia suspension and incubated at different temperatures during different wet chamber periods. Incidence and severity of the disease were evaluated daily. Sporulation was evaluated at the end of each treatment. The favorable range of temperature to conidia germination of M. laxa, from 5 to 30ºC, was greater than M. fructicola range, from 10 to 30ºC. The wetness duration showed no influence on conidia germination. The best range of temperature for mycelial growth of both M. fructicola and M. laxa was from 20 to 25ºC. Sporulation of M. laxa showed an inverse relationship to the incubation temperature. No relationship between temperature and conidia production was found for M. fructicola. Both species were sensitive to the iminoctadine fungicide in vitro. Incidence of brown rot was greater than 80.9% in all treatments, for both species. At 10ºC incubation and latency periods were shorter for M. laxa than for M. fructicola. The best temperatures for lesion development varied between 15 and 25ºC for both pathogens. Sporulation of the two species showed no relationship to the temperature on the in vivo trials. Visual differences were observed on pathogen symptoms on fruit.

Resumo: Dos vírus que infectam o maracujazeiro no Brasil, atualmente o Cowpea aphid borne mosaic virus (CABMV), é considerado fator limitante à cultura. Dependendo da velocidade de disseminação e idade com que as plantas são infectadas no campo, a cultura torna-se comercialmente improdutiva. O presente estudo teve como objetivo, avaliar a diversidade e a dinâmica populacional dos afídeos na região da Alta Paulista, SP e a possibilidade de transmissão do vírus pela semente. Assim, quatro locais (Leste e Oeste da cidade de Marília e Municípios de Ocauçú e Guaimbê) foram monitorados durante 24 meses com armadilhas amarelas de água do tipo Moericke. Constatou-se nas quatro regiões a predominância do gênero Aphis. Outras espécies coletadas foram Myzus persicae, Geopenphigus flocculosus, Brevicoryne brassicae, Rhopalosiphum spp, Dysaphis spp e Lipaphis erysimi. A flutuação populacional de formas aladas do gênero Aphis, caracterizou-se por apresentar maiores revoadas em maio, junho, agosto e setembro. As espécies de Aphis (A. fabae, A. gossypii, A. spiraecola) devem ser os principais vetores do CABMV na região. Plantios novos, ao lado de plantações infectadas, tornam-se infectadas em três meses. Nos testes de transmissão através de sementes, do total de 13056 semeadas oriundas de plantas doentes, germinaram 10592, e em avaliações visuais dois meses após a germinação, não foram observadas plantas sintomáticas, indicando a não transmissão pela semente.
Abstract: From the viruses were described infecting passionfruit plants in Brasil, and the Cowpea aphid borne mosaic virus (CABMV), is considered the most hazardous. Depending on the spread velocity of aphids and the age that the plants are infected, the crops doesn’t produce commercial fruits. The present study was designed to evaluate the diversity and dynamic population of aphids in the Alta Paulista, SP region and aspects of seed transmission. For this, four regions (East and West of Marília city, Guaimbê and Ocauçú) were monitored for 24 months using yellow water Moerick trap. The predominance of the genus Aphis was observed in the four evaluated areas. Other species founded in the area were: Myzus persicae, Geopenphigus flocculosus, Brevicoryne brassicae, Rhopalosiphum spp, Dysaphis spp and Lipaphis erysimi. The population curve of alate Aphis spp showed the highest frequency of flights during May, June, August and September. The Aphis spp (A. fabae, A. gossypii, A. spiraecola) probably is the most important vector of the CABMV in the region. New crops near old infected plants, were infected in three months. To evaluate properties of seed transmission, from 13056 collected from infected plants, 10592 were germinated and evaluated during two months for the presence of visual symptoms. No plants with simptoms were observed indicating no seed transmission.
Orientador: Marcelo Agenor Pavan
Coorientador: Valdir Atsushi Yuki
Banca: Renate Krause Sakate
Banca: Aloisio Costa Sampaio
Banca: Alexandre Levi R. Chaves
Banca: Hugo Kuniyuki
Doutor

A duração do período de molhamento (DPM) é de grande importância para a epidemiologia de doenças de plantas, pois desempenha papel fundamental em alguns processos epidemiológicos. Dessa forma, sua determinação torna-se indispensável para o entendimento da relação entre o clima e doenças de plantas. Sendo assim, este estudo teve como objetivos: definir uma posição padrão de instalação de sensores cilíndricos para a medida da DPM sobre gramado, avaliar a variabilidade espacial dessa variável em três diferentes culturas, relacionar a DPM medida em culturas agrícolas com aquela obtida em posto meteorológico e comparar a estimativa da DPM obtida com modelos empíricos com aquela medida com sensores eletrônicos. Na fase anterior à sua instalação no campo, todos os sensores eletrônicos foram previamente pintados com tinta látex e tratados termicamente. Após essa etapa, os sensores cilíndricos foram instalados sobre gramado a 30 cm de altura voltados para o sul. No período inicial, os sensores cilíndricos foram mantidos paralelos à horizontal, visando-se a avaliar a variabilidade entre os mesmos. Posteriormente, foram testados cinco diferentes ângulos de instalação. As medidas obtidas por esses sensores foram comparadas com a medida padrão, obtida por sensor de placa a 30 cm de altura e 45º de inclinação. Com a finalidade de se avaliar a variabilidade espacial da DPM, sensores eletrônicos de DPM foram distribuídos no dossel de três culturas: algodão, banana e café. As medidas obtidas nessas culturas foram comparadas com as fornecidas por sensor de placa em posição padrão. A estimativa da DPM foi feita por meio dos seguintes modelos: NHUR > 87%, CART, DPO e limiar estendido de umidade relativa para os períodos seco e chuvoso. As medidas obtidas por sensores cilíndricos sobre gramado apresentaram boa acurácia e precisão. A variação do ângulo de instalação não demonstrou ter efeito expressivo sobre a medida dos sensores cilíndricos para as condições locais. Contudo, é recomendável inclinar o sensor cilíndrico, uma vez que, trabalhos anteriores demonstram que esse pode superestimar a DPM quando instalado na horizontal. A avaliação da variabilidade espacial da DPM demonstrou que essa variável é influenciada pelas condições determinantes do microclima das culturas. O padrão de variação da DPM foi distinto para cada uma das culturas. Na cultura do algodão não foram observadas variações expressivas da DPM. Já no cafeeiro a DPM foi mais longa nas partes baixas da planta, enquanto que na cultura da banana essa foi mais longa no topo da cultura. Foram obtidas boas relações entre a DPM medida sobre gramado e aquela obtida no topo das culturas, demonstrando que é possível estimar tal variável por meio de dados obtidos em posto meteorológico. Os modelos NHUR > 87%, CART e DPO forneceram boas estimativas da DPM com erro absoluto médio variando de 1,4 a 2,8 h nos dois períodos avaliados. Durante a estação seca, os três primeiros modelos tenderam a subestimar a DPM. O modelo do limiar estendido de umidade relativa foi o que apresentou o pior desempenho entre os modelos avaliados, não sendo recomendável sua aplicação para condições semelhantes às deste estudo.
Leaf wetness duration (LWD) is a very important variable for plant disease epidemiology, since it plays an important role in some epidemiological processes. So its determination is essential for the understanding of the climate and plant disease relationship. Therefore, the objectives of this study were: to determine the standard deployment for cylindrical LWD sensors over turfgrass; to assess the spatial variability of this variable in three different crops; to relate the LWD measured at three different crop canopies to that obtained in a weather station; and to compare the LWD estimated by empirical model with that measured by electronic sensors. Before the field assessments, all electronic sensors were painted with white latex paint and submitted to a heat treatment. After this first stage, all cylindrical sensors where installed over turfgrass at 30-cm height deployed facing south. Firstly, all cylindrical sensors were deployed at horizontal in order to assess the variability among them. After that, five different deployment angles were tested. The measurements provided by those sensors were compared with the standard measurement, provided by flat plate sensors at 30-cm height and deployed at 45º. In order to assess the LWD spatial variability, electronic sensors were placed in three different crop canopies: cotton, banana and coffee. The measurements obtained in those crops were compared with LWD measured by flat plate sensors in a standard deployment over turfgrass. LWD were estimated using the following models: NHRH>87%, CART, DPD e extended threshold of relative humidity, for the dry and wet seasons. The measurements provided by cylindrical sensors over turfgrass had good accuracy and precision. The change in the angle of sensor deployment had no effect on LWD measured by cylindrical sensors, for the studied conditions. However, cylindrical sensors should not be deployed at horizontal because previous studies showed that they could overestimate LWD when deployed at horizontal. The LWD spatial variability assessment showed that this variable is dependent on the plant and/or crop conditions, which control the canopy microclimate. The pattern of variation of LWD was different for each crop assessed. In the cotton crop, LWD variations were negligible. On the other hand, in the coffee crop LWD was longer in the lower parts of the canopy while in the banana crop it was longer in the top of the canopy. A good correlation between LWD measured over turfgrass and that obtained in the crop top was achieved, which demonstrates that it is possible to estimate LWD using weather station data. The models NHRH>87%, CART, DPD provided good estimates of LWD with mean absolute error ranging from 1.4 to 2.8 h in both dry and wet periods. During the dry season, those models overestimated the LWD. The extended threshold model had the worst performance in relation to the other models, so it is not advised to use this model for similar climate conditions to this study.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Dos vírus que infectam o maracujazeiro no Brasil, atualmente o Cowpea aphid borne mosaic virus (CABMV), é considerado fator limitante à cultura. Dependendo da velocidade de disseminação e idade com que as plantas são infectadas no campo, a cultura torna-se comercialmente improdutiva. O presente estudo teve como objetivo, avaliar a diversidade e a dinâmica populacional dos afídeos na região da Alta Paulista, SP e a possibilidade de transmissão do vírus pela semente. Assim, quatro locais (Leste e Oeste da cidade de Marília e Municípios de Ocauçú e Guaimbê) foram monitorados durante 24 meses com armadilhas amarelas de água do tipo Moericke. Constatou-se nas quatro regiões a predominância do gênero Aphis. Outras espécies coletadas foram Myzus persicae, Geopenphigus flocculosus, Brevicoryne brassicae, Rhopalosiphum spp, Dysaphis spp e Lipaphis erysimi. A flutuação populacional de formas aladas do gênero Aphis, caracterizou-se por apresentar maiores revoadas em maio, junho, agosto e setembro. As espécies de Aphis (A. fabae, A. gossypii, A. spiraecola) devem ser os principais vetores do CABMV na região. Plantios novos, ao lado de plantações infectadas, tornam-se infectadas em três meses. Nos testes de transmissão através de sementes, do total de 13056 semeadas oriundas de plantas doentes, germinaram 10592, e em avaliações visuais dois meses após a germinação, não foram observadas plantas sintomáticas, indicando a não transmissão pela semente.
From the viruses were described infecting passionfruit plants in Brasil, and the Cowpea aphid borne mosaic virus (CABMV), is considered the most hazardous. Depending on the spread velocity of aphids and the age that the plants are infected, the crops doesn t produce commercial fruits. The present study was designed to evaluate the diversity and dynamic population of aphids in the Alta Paulista, SP region and aspects of seed transmission. For this, four regions (East and West of Marília city, Guaimbê and Ocauçú) were monitored for 24 months using yellow water Moerick trap. The predominance of the genus Aphis was observed in the four evaluated areas. Other species founded in the area were: Myzus persicae, Geopenphigus flocculosus, Brevicoryne brassicae, Rhopalosiphum spp, Dysaphis spp and Lipaphis erysimi. The population curve of alate Aphis spp showed the highest frequency of flights during May, June, August and September. The Aphis spp (A. fabae, A. gossypii, A. spiraecola) probably is the most important vector of the CABMV in the region. New crops near old infected plants, were infected in three months. To evaluate properties of seed transmission, from 13056 collected from infected plants, 10592 were germinated and evaluated during two months for the presence of visual symptoms. No plants with simptoms were observed indicating no seed transmission.

Recentemente, um fitoplasma do grupo 16SrIX foi associado a plantas de citros com sintomas de huanglongbing (HLB) no Estado de São Paulo. No entanto, em razão da ampla diversidade de fitoplasmas que tem se observado em várias culturas no Brasil, seria possível que além do fitoplasma do grupo16SrIX, outros fitoplasmas também pudessem estar associados a plantas de citros no Estado de São Paulo. Sendo assim, o objetivo deste estudo foi investigar se outros fitoplasmas, além daquele do grupo 16SrIX, estão associados a plantas de citros no Estado de São Paulo. Amostras foliares de plantas de citros, plantas daninhas e cicadelídeos foram coletados entre os meses de Junho a Outubro de 2010, em pomares localizados em quatro municípios: Araraquara, Bebedouro, Piracicaba e Taquarituba. Análises de nested PCR evidenciaram a presença de fitoplasmas associados a plantas de citros (sintoma: clorose foliar); a plantas daninhas: Bidens pilosa (sintomas: filodia e virescência), Leonorus sibiricus (sintoma: deformação foliar), Solanum americanus (sintoma: superbrotamento foliar), Erigeron bonariensis (sintomas: avermelhamento e superbrotamento foliar) e Euphorbia heterophylla (sintoma: deformação foliar); e a cicadelídeos da espécie Agallia albidula (Uhler, 1895) (subfamília Agalliinae). A confirmação da presença e caracterização molecular dos fitoplasmas foi realizada através de análises de RFLP e seqüenciamento da região 16S rDNA. Uma ampla diversidade de fitoplasmas foi identificada. Fitoplasmas dos grupos 16SrIII e 16SrIX foram associados a plantas de citros em Piracicaba, enquanto um fitoplasma do grupo 16SrVII foi associado a plantas de citros em Bebedouro. Fitoplasmas do grupo 16SrIII foram associados a plantas daninhas das espécies B. pilosa, L. sibiricus e S. americanus em Piracicaba e fitoplasmas do grupo 16SrVII foram associados a plantas de E. bonariensis e E. heterophylla em Piracicaba e Taquarituba, respectivamente. Um fitoplasma do grupo 16SrIII foi associado a A. albidula em Taquarituba, sugerindo ser este um potencial inseto vetor de fitoplasmas em pomares de citros. Com base na análise da região 16S rDNA, muitos dos fitoplasmas encontrados apresentaram-se distintos dos fitoplasmas já relatados. Em virtude disto, estes fitoplasmas foram propostos como representantes de novos subgrupos pertencentes aos grupos 16SrIII, 16SrVII e 16SrIX. Os resultados obtidos neste estudo não nos permite a associação dos fitoplasmas encontrados com o HLB ou qualquer outra doença já descrita, sendo, portanto, necessários mais estudos visando confirmar o papel destes fitoplasmas como patógenos de citros e plantas daninhas.
Recently a phytoplasma of the 16SrIX group was associated with citrus trees exhibiting symptoms of huanglongbing (HLB) in Sao Paulo state. However, due to the wide diversity of phytoplasmas that have been observed in several crops in Brazil, it is possible that in addition to the phytoplasma of group 16SrIX other phytoplasmas could also be associated with citrus trees. Therefore, the objective of this study was to investigate if others phytoplasmas besides that of the 16SrIX group are associated with citrus plants in the São Paulo state. Leaf samples from citrus trees, weeds and cicadellids were collected between June and October of 2010 from citrus orchards of four municipalities of the Sao Paulo state: Araraquara, Bebedouro, Piracicaba and Taquarituba. Nested PCR analysis revealed the presence of phytoplasmas associated with citrus trees (symptom: leaf chlorosis), weeds: Bidens pilosa (symptoms: phyllody and virescence), Leonorus sibiricus (symptom: leaf distortion), Solanum americanus (symptom: witches broom), Erigeron bonariensis (symptoms: redning and witches broom) e Euphorbia heterophylla (symptom: leaf distortion); and cicadellids of specie Agallia albidula (Uhler, 1895) (subfamily Agalliinae). The confirmation of the phytoplasma presence and molecular characterization was carried out by RFLP analysis and sequencing of the 16S rDNA region. A wide diversity of phytoplasmas was verified. Phytoplasmas of the 16SrIII and 16SrIX groups were associated with citrus trees in Piracicaba, while a phytoplasma of the 16SrVII group was associated with citrus trees in Bebedouro. Phytoplasmas of the 16SrIII group were associated with weeds belonging to the species B. pilosa, S. americanus and L. sibiricus in Piracicaba and a phytoplasma of the 16SrVII group was identified associated with plants of E. bonariensis and E. heterophylla in Piracicaba and Taquarituba, respectively. A phytoplasma of the 16SrIII group was associated with A. albidula in Taquarituba, suggesting that this cicadelid is a potential vector of phytoplasmas in citrus orchards. Based on the analysis of the 16S rDNA region, many of the found phytoplasmas are distinct from those already reported. Due to this distinction, these phytoplasmas were proposed as representatives of new subgroups of the groups 16SrIII, 16SrVII and 16SrIX. The results of this study dont allow us associate the found phytoplasmas with HLB or any other described disease. Thus, more studies are needed to identify the role of theses phytoplasmas as pathogens of citrus trees and weeds.

O presente trabalho objetivou estudar tanto o progresso da Clorose Variegada dos Citros no tempo, quanto o arranjo espacial das plantas afetadas, visando caracterizar a dinâmica da doença em três regiões do Estado de São Paulo (Noroeste, Centro e Sul). Por meio de avaliação de sintomas visuais, foram mapeados, bimensalmente, três talhões de laranja-doce Pêra enxertada em limão Cravo, em três regiões do Estado de São Paulo, desde julho de 1998 até dezembro de 2000. O progresso no tempo foi avaliado por meio de ajuste a modelos matemáticos e análise das curvas de derivada. As curvas de progresso da CVC não puderam ser ajustadas a modelos conhecidos. O progresso da CVC apresentou diversos picos de derivada, em sua maioria coincidindo com a primavera e o verão. Para o estudo da dinâmica espacial, foram aplicadas as seguintes análises: seqüências ordinárias; áreas isópatas; lei de Taylor modificada; índice de dispersão e análise de dinâmica e estrutura de focos. Essas análises demonstraram pouca diferença no padrão espacial da doença entre as regiões, que pode ser considerado levemente agregado. Por meio de análise de autocorrelação, de densidade espectral, análise discriminante, e correlação de lags, procurou-se também estabelecer padrões na evolução de emissão de brotações pelas plantas, expressão de sintomas e detecção de infecções assintomáticas e a correlação dessas variáveis entre si e com o clima. Também foi feita a comparação entre estações do ano e regiões por meio de testes não-paramétricos. Número de novas brotações foi a variável que mais distinguiu entre as três regiões. As variáveis relacionadas à doença (infecções assintomáticas, infecções totais, sintomas e concentração bacteriana) apresentaram padrões sazonais, mas não foi observada diferença estatística entre as estações do ano. O pomar da região Noroeste apresentou maior quantidade de brotações novas e maior quantidade de sintomas. O pomar da região Sul apresentou maior quantidade de infecção assintomática. Não houve diferença de concentração bacteriana entre os pomares das três regiões.
This work aimed to evaluate the progress and spatial pattern of Citrus Variegated Chlorosis (CVC) in three regions in the state of São Paulo, Brazil. By bimonthly visual assessments three Pêra sweet orange/ Rangpur lime orchards in three regions (Northwest, Center and South) were mapped from july 1998 to december 2000. Progress was evaluated by fitting nine models do disease progress curves and by analysis of derivative curves. No model could be fitted to disease progress curves. Derivative curves showed peaks concentrated in spring and summer. To characterize spatial pattern the following analysis were used: ordinary runs, isopath areas;binary Taylor law; dispersion index and foci dynamics and structure analysis. All techniques showed small differences between regions and characterized CVC spatial pattern as slightly aggregated. By means of autocorrelation, spectral density analysis, discriminant analysis and lag correlation was tried to establish temporal patterns for vegatative flush emission, symptom expression, detection of assymptomatic infections. Also, was tried to establish correlations among variables and between them and weather variebles. A comparison by non-parametric tests was made between seasons and regions. Number of new vegetative flushes was the most distinctive variables for regions. The disease related variables (assymptomatic infections, total infection, symptoms and relative bacteria concentration) showed seasonal patterns but no statistical difference was found between seasons. Northwest orchard showed higher number of vegetative flushes. South orchard assymptomatic infections were higher than for the other orchards. There was no difference in relative bacteria concentration between regions.

Orientadores: Stanley Robson de Medeiros Oliveira, Carlos Alberto Alves Meira
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agrícola
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Resumo: A ferrugem asiática, causada pelo fungo Phakopsora pachyrhizi, atualmente é considerada uma das doenças mais importantes e agressivas da soja. A principal forma de controle é a aplicação calendarizada de fungicidas a qual desconsidera o risco de ocorrência da doença. Estudos epidemiológicos buscam compreender os fatores que influenciam na ocorrência e desenvolvimento das epidemias, especialmente aqueles relacionados ao ambiente tais como condições meteorológicas. Com o avanço da tecnologia da informação e do armazenamento de dados, técnicas de mineração de dados (data mining) apresentam-se promissoras para a descoberta de conhecimento em bases de dados epidemiológicos. Este trabalho tem como objetivo avaliar a influência da chuva e da temperatura na ocorrência da ferrugem asiática da soja utilizando árvores de decisão. Para tal, foram obtidos dados de ocorrências da doença em quatro safras, de 2007/2008 a 2010/2011, oriundos do banco de dados do Consórcio Antiferrugem, e dados meteorológicos, provenientes do sistema Agritempo. A análise exploratória dos dados permitiu obter subsídios para compor o conjunto de dados final e definir o escopo deste trabalho, buscando-se características intrínsecas à doença e sua interação com o ambiente, utilizando apenas variáveis de base meteorológica. As variáveis utilizadas foram relacionadas à precipitação e à temperatura, que deram origem a nove atributos avaliados para cada período temporal...Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digital
Abstract: The Asian soybean rust, caused by Phakopsora pachyrhizi, is now considered one of the most important and aggressive diseases of soybean. The main form of control is the scheduled application of fungicides which disregards the the risk of disease occurrence. Epidemiological studies seek to understand the factors that influence the occurrence and development of epidemics, especially those related to the environment such as weather conditions. With the development of information technology and data warehousing, data mining techniques appear to be promising for knowledge discovery in epidemiological databases. This study aims to evaluate the influence of rainfall and temperature on the occurrence of soybean rust by using decision trees models. To accomplish that, data of the occurence of the disease were collected from four seasons, 2007/2008 to 2010/2011, from the Consórcio Antiferrugem and weather data from the Agritempo system. Exploratory data analysis allowed for obtaining subsidies to generate the final data set and define the scope of this work, seeking intrinsic characteristics of the disease and its interaction with the environment, using only meteorological variables. The variables used were related to precipitation and temperature, resulting into nine attributes evaluated in different periods. Such attributes were related to the event of occurrence (Oc) and non occurrence (NaoOc) of the disease (assumed as the thirtieth day prior to the event of occurrence). The results include a predictive model and an interpretive model for classifying events of occurrences and non occurrences of the disease...Note: The complete abstract is available with the full electronic document
Mestrado
Planejamento e Desenvolvimento Rural Sustentável
Mestre em Engenharia Agrícola

A Clorose Variegada dos Citros (CVC), causada pela bactéria Xylella fastidiosa, é atualmente a doença de maior incidência no Estado de São Paulo. A incidência e a severidade da doença são maiores nas regiões Norte e Noroeste do Estado, onde o clima é predominantemente quente e com déficit hídrico, principalmente no inverno. Embora não haja nada comprovado, alguns estudos indicam que o déficit hídrico aumenta a severidade dos sintomas nas plantas afetadas pela CVC. Além disso, até hoje não foi estabelecida uma função que relacione doença e dano. Dessa forma, o estudo presente objetivou avaliar o efeito de diferentes níveis de irrigação no progresso poliético da CVC, avaliar métodos de avaliação da doença e determinar uma função de dano para a CVC. Para isso, um experimento foi instalado no município de Bebedouro, região Norte do Estado de São Paulo sob o delineamento blocos ao acaso no esquema fatorial 3 x 2, com os seguintes tratamentos: sem irrigação, irrigado com 50% e 100% da evapotranspiração da cultura (ETc), combinados com inoculação natural e artificial de X. fastidiosa. Cada parcela foi constituída de 6 plantas úteis, havendo 4 repetições de cada tratamento, totalizando 144 plantas úteis. As variáveis quantificadas em cada árvore do experimento foram: (a) produção, considerando frutos assintomáticos e sintomáticos, no período de 2006 a 2008 e produção total referente às safras 2001 a 2005; (b) intensidade da doença, através da incidência de ramos com sintomas da CVC e utilizando uma escala descritiva; (c) vigor da planta, estimado pela medida da altura da planta, diâmetro da copa, diâmetro do tronco, volume de copa e do índice de área foliar (IAF). O modelo monomolecular foi utilizado para descrever o progresso poliético da incidência da CVC, no período de 2006 a 2008, para todos os tratamentos. A partir desse modelo foi possível observar que plantas sem irrigação apresentam maior incidência de ramos com sintomas que plantas irrigadas a 100% da ETc, principalmente quando inoculadas de forma artificial. Esse resultado ficou ainda mais evidenciado quando se avalia o número de frutos com sintomas (ø < 50mm) da CVC por tratamento. Também foi possível observar que os sintomas nas plantas são distribuídos de forma irregular, apresentando um gradiente decrescente significativo da parte superior para inferior. As variáveis relacionadas ao vigor da planta, na sua maioria, não apresentaram relação alguma com a produção em todos os tratamentos. De modo geral, as plantas do tratamento irrigado a 100% da ETc combinado com inoculação natural apresentaram maior produção total, considerando as safras de 2001 a 2008. A relação entre CVC e dano pode ser descrita pela equação (y=114,067*exp(-0,017555)*x) onde y é a produção da planta em Kg e x a incidência de ramos com CVC em porcentagem. A escala descritiva não permitiu avaliação precisa e apresentou baixa correlação entre os avaliadores, o contrário foi observado realizando a avaliação da CVC através da incidência de ramos com sintomas.
The Citrus Variegated Chlorosis (CVC) caused by the bacteria Xylella fastidiosa is nowadays the disease with the most incidence in the state of São Paulo. The incidence and severity of the disease are greater in the Northern and Northwestern regions of the state where the climate is predominately warm and presents a water deficits especially in the winter. Although there is no definite proof, some studies indicate that the water deficits increases the severity of the symptoms in plants affected by the CVC. Besides, up to the present there has not been a function which relates the damage to an intensity of the disease. In that manner, the present study has been conducted in order to evaluate the effect of different irrigation levels on the polyetic progress of the CVC as well as to study methods of assessment of the disease and determine the relationship between disease intensity and yield. In order to carry out this study, an experiment was conducted in the city of Bebedouro north of São Paulo state. The experimental design was in randomized blocks in a 3 x 2 factorial scheme with the following treatments: no irrigation, irrigated with 50% and 100% of the evapotranspiration of the crop (ETc), combined with natural and artificial inoculation of X. fastidiosa. Each group was made of 6 useful plants, with 4 repetitions for each treatment, totalizing 144 useful plants. The variables quantified in each tree of the experiment were: (a) (a) yield, considering asymptomatic and symptomatic fruit in the period 2006 to 2008 and total yield on the crops from 2001 to 2005; (b) intensity of the disease through incidence of branches with symptoms of CVC and using a descriptive scale; (c) plant vigor, estimated through measure of height, crown diameter, trunk diameter, canopy volume and of the leaf area index (LAI). The monomolecular model was used to describe the polyetic progress of CVC incidence between 2006 and 2008 for all treatments. From this model it was possible to observe that plants without irrigation present greater incidence of branches with symptoms than the ones irrigated at 100% of ETc, especially when inoculated in an artificial manner. This result was even more evident when the number of fruit with symptoms is evaluated (ø < 50mm) of CVC per treatment. It was also possible to observe that the symptoms in the plants are scattered in an irregular way, presenting a significant decreasing rate from the upper to the lower part. Most of the variables related to the plant vigor did not present any relation to the production in all treatments. In general, the plants from the irrigated treatment at 100%of ETc combined with natural inoculation presented more total yield considering the harvests from 2001 to 2008. The relationship between CVC and damage can be described by the equation (y=114,067*exp(-0,017555)*x) where y is the plant yield in Kg and x is the incidence in percentage of branches with CVC. The descriptive scale did not allow accurate assessment and showed a low correlation between the raters, the opposite was observed performing the assessment of CVC through the incidence of branches with symptoms.

A podridão parda do pessegueiro é uma das principais doenças da cultura no Estado de São Paulo e na maioria das regiões produtoras do mundo. No Brasil, seu agente causal é o fungo Monilinia fructicola (Wint) Honey, que infecta ramos, flores e frutos tanto em pré como em pós-colheita. A compreensão do comportamento epidemiológico da podridão parda do pessegueiro em condições tropicais é fundamental para o estabelecimento de estratégias de controle mais eficientes nos pomares brasileiros. Neste contexto o presente trabalho teve como objetivo caracterizar o progresso temporal e a distribuição espacial da epidemia da podridão parda do pessegueiro, em pomares comerciais sob condições naturais de infecção. O estudo foi realizado em áreas comerciais não tratadas e tratadas com fungicidas, em dois pomares no Estado de São Paulo, em 2005 e 2006. Realizaram-se amostragens quinzenais de frutos durante 3 meses após o florescimento. Foram colhidos, pelo menos, 300 frutos por amostragem, os quais foram tratados com o herbicida gramoxone para detecção da infecção latente. A análise temporal dos dados foi realizada por regressão não-linear entre a incidência da doença e o tempo, enquanto a distribuição espacial de frutos doentes foi avaliada por meio do índice de dispersão (D) e da lei de Taylor modificada, que relacionam variâncias observada e binomial. Nos dois anos e locais estudados, a podridão parda apresentou tendência de crescimento exponencial, com baixa incidência no início das amostragens e aumento expressivo no início da maturação dos frutos. O modelo exponencial apresentou melhor ajuste aos dados, nos dois anos e locais de estudo. Em 2005, a incidência da doença chegou a valores máximos no ponto de colheita, atingindo 70% em frutos de plantas tratadas e 66,4% nos de não tratadas. Nesse ano, a incidência da podridão parda em frutos de plantas sem e com fungicidas não diferiram entre si (P>0,05), tanto nos parâmetros do modelo quanto na área abaixo da curva de progresso da doença (AUDPC). Em 2006, as curvas de progresso da doença, para frutos de plantas não tratadas com fungicidas, foram semelhantes entre si e caracterizaram-se pelo rápido aumento da incidência de infecções a partir da maturação dos frutos, chegando, na última avaliação, a 59,17% em Holambra II e 74,37% em Jarinu. O controle químico foi eficiente em 2006, havendo baixa incidência de podridão parda em frutos de plantas tratadas, durante toda safra e nos dois locais. No pomar avaliado em 2005, a agregação de frutos doentes (4,7The brown rot of peach is one of the main diseases in peach orchards in the State of São Paulo and in most peach producing regions in the world. In Brazil, brown rot is caused by the fungus Monilinia fructicola and it attacks stems, blossoms and fruits in the pre and post harvest periods. The understanding of the brown rot epidemiologic behavior in tropical conditions is essential to the establishment of more efficient control strategies in Brazilian orchards. In this context, the present work aimed to characterize the temporal progress and the spatial distribution of the peach brown rot in commercial orchards under natural infection conditions. The study was carried out in untreated and fungicide-sprayed commercial areas in Paranapanema and Jarinu, SP, in 2005 and 2006. Fruit samplings were performed fortnightly during 3 months after blooming. At least 300 fruits were collected in each sampling and treated with gramoxone herbicide to detect latent infection. Temporal data analysis was done by non-linear regression between disease incidence (y) and time (x). The spatial pattern of diseased fruit was assessed by the dispersion index (D) and the modified Taylor?s power law which relate observed and binomial variances. During these two years in the area studied, brown rot presented a tendency for exponential growth with low incidence in the beginning of the season and expressive increase in the beginning of fruit ripening. The exponential model presented a better fit to the data for the two year study period. In 2005, the brown rot incidence reached maximum values during the harvest: 70% in treated trees and 66,4% in untreated trees. There was no significant difference (P>0.05) in brown rot incidence in trees with or without fungicide treatment in model parameters as well as in the area under the disease progress curve (AUDPC). In 2006, the disease progress curves for treated and untreated trees were not similar. Disease progress curves for untreated trees were characterized by the rapid increase in infections incidence after the ripening of the fruit, reaching in the last evaluation, 59,17% for Holambra II and 74,37% in Jarinu. Chemical control was effective in 2006, with low brown rot incidence in treated trees throughout the harvest in both sites. In the orchard evaluated in 2005, the aggregation of diseased fruit (4,7