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A antracnose foliar do milho (Zea mays) (Colletotrichum graminicola) é considerada uma das principais doenças foliares da cultura. Dentre as estratégias de controle, a utilização de materiais genéticos resistentes é uma das mais eficientes, contudo, para a identificação de novas fontes de resistência, torna-se necessário o desenvolvimento e a padronização de metodologias que permitam a determinação precisa da reação dos genótipos que são avaliados. Considerando a inexistência de métodos padronizados para a reprodução dos sintomas de antracnose foliar, este trabalho teve como objetivo determinar o método mais eficiente e prático para a inoculação de C. graminicola em folhas de milho. Para tanto, foi conduzido um experimento em câmara de crescimento, utilizando a linhagem endogâmica (L95-1), considerada suscetível à antracnose foliar e pertencente ao Programa de Melhoramento Genético de milho da Universidade Estadual de Ponta Grossa. As plantas foram cultivadas em vasos individuais, os quais foram dispostos em delineamento inteiramente casualizado, composto por três repetições. A inoculação foi realizada no estádio vegetativo V7, com suspensão de esporos na concentração de 3,2 x 106 conídios mL-1. Os métodos de inoculação testados foram: pulverização da suspensão de conídios sobre as folhas do cartucho até o ponto de escorrimento; pulverização da suspensão de conídios até o ponto de escorrimento, sobre as folhas do cartucho feridas com lâmina; deposição de 5 mL da suspensão de conídios no cartucho, e plantas sem inoculação (testemunha). A avaliação da severidade da doença foi realizada no estádio vegetativo V13, a partir da comparação dos sintomas com escala de notas de 0 (lesões necróticas de até 1 mm) a 5 (lesões necróticas de 60 a 150 mm). A partir dos dados de severidade, foi determinado os índices de doença (ID), os quais foram submetidos a análise de variância, e as médias comparadas pelo teste de Tukey (p < 0,05). Os resultados mostraram que houve diferença significativa entre os métodos de inoculação testados. A pulverização da suspensão de conídios sobre as folhas do cartucho até o ponto de escorrimento não diferiu significativamente da pulverização da suspensão de conídios até o ponto de escorrimento, sobre as folhas do cartucho feridas com lâmina, com ID de 29,99 e 28,89%, respectivamente. Conclui-se que o melhor método de inoculação de C. graminicola em folhas de milho foi através da deposição da suspensão de conídios no cartucho (ID de 42,22%), pois além de ter culminado numa maior severidade da doença, apresentou maior facilidade, praticidade e rapidez na execução da inoculação

No atual cenario da agricultura, o controle biologico de doencas vem ganhando importância. O controle biologico nao e so a interacao entre patogeno, hospedeiro e ambiente, mas o resultado desta interacao. Os mecanismos das interacoes antagonistas podem ser: antibiose, competicao, parasitismo, predacao e inducao de defesa do hospedeiro. O objetivo deste trabalho foi avaliar o efeito de agentes antagonistas no crescimento de fitopatogenos in vitro . O experimento foi conduzido no delineamento inteiramente ao acaso, com seis repeticoes. Os antagonistas testados foram Trichoderma asperellum e Bacillus subtilis e os fitopatogenos: Sclerotium rolfsii , Sclerotinia sclerotiorum , Rhizoctonia solani , e Colletotrichum dematium var. truncata . Para determinar o antagonismo foi utilizado o metodo do pareamento de colonias e para avaliar os efeitos dos produtos metabolicos toxicos volateis dos antagonistas sobre os fungos fitopatogenicos, foi utilizado o metodo de Gibbs. Pelo teste de culturas pareadas, T. asperellum colonizou e produziu esporos sobre S. rolfsii , S. sclerotiorum e C. dematium var truncata e houve formacao do halo de inibicao apenas para R. solani . T. asperellum mostrou potencial para antagonizar S. rolfsii , R. solani e C. dematium var truncata pelo metodo de producao de metabolitos toxicos. Nao houve formacao de esclerodios. B. subtilis mostrou-se eficiente no controle de S. sclerotiorum e S. rolfsii , mas nao impediu que formassem esclerodios. T. asperellum mostrou-se mais eficiente que B. subtilis no controle biologico dos fitopatogenos S. rolfsii , S. sclerotiorum e R. solani .

O feijao e uma cultura de extrema importância economica e alimentar para a populacao brasileira. A incidencia e severidade de doencas podem causar declinio na produtividade e qualidade do produto final. Uma das principais doencas da cultura e a antracnose (Colletotrichum lindemuthianum) que, caso nao haja controle, pode ocasionar em danos de ate 100% na producao. O objetivo deste trabalho foi avaliar a viablidade de fungos endofiticos, acido salicilico, fosfito de cobre, acibenzolar-S-metilico e fungicida (azoxistrobina + difenoconazol) no controle da antracnose. Os experimentos foram conduzidos em casa de vegetacao, com as cultivares de feijao IPR Tuiuiu, IPR Uirapuru, IPR Quero-quero e BRS Esteio. O delineamento experimental utilizado foi em blocos aleatorizados, com sete tratamentos e quatro repeticoes. Com os dados de severidade calculou-se a area abaixo da curva de progresso da doenca. Os produtos alternativos nao foram eficazes para reduzir o progresso da antracnose nas plantas de feijao das cultivares avaliadas. A aplicacao dos fungos T. viride e T. tomentosum resultou em comportamento similar ao fungicida azoxistrobina + difenoconazol em todas as cultivares avaliadas, podendo ser alternativa ao controle quimico. A aplicacao de fosfito de cobre resultou em maior severidade da antracnose.

O metodo da folha destacada apresenta as vantagens de economia de espaco, facilidade e exatidao das observacoes, menor risco de contaminacoes e uniformidade da unidade experimental. Esse metodo tem sido usado para testes rapidos de inducao de resistencia. Assim, o objetivo deste trabalho foi avaliar diferentes produtos na inducao de resistencia em folhas de soja para Phakopsora pachyrhizi , Sclerotinia sclerotiorum e Rhizoctonia solani pelo metodo da folha destacada modificado. O delineamento experimental foi o inteiramente casualizado em esquema fatorial 7 (tratamentos) x 2 (aplicacao ou nao do produto em metade da mesma folha), com cinco repeticoes. Os tratamentos foram: 1 – testemunha, agua; 2 - acibenzolar-S-metilico; 3 - calcio; 4 - micronutrientes: cobre, manganes e zinco; 5 -micronutrientes: manganes, zinco e molibdenio; 6 - adubo NK e 7 - Ascophyllum nodosum . Nao houve diferenca dos tratamentos para P. pachyrhizi nos dois experimentos. Os micronutrientes manganes, zinco e molibdenio e a alga A. nodosum apresentam potencial de inducao de resistencia sistemica a S. sclerotiorum em folhas de soja nos dois experimentos. Para R. solani destacaram-se os tratamentos com os micronutrientes: cobre, manganes e zinco e manganes, zinco e molibdenio, respectivamente, com reducao da AACPD apenas no local onde foram aplicados nos dois experimentos.

Beans (Phaseolus vulgaris) are extremely important because it is included daily in the diet of themajority of the Brazilian population. Several factors negatively affect the productivity of this crop, especially diseases.One of the main ones is anthracnose (Colletotrichum lindemuthianum), which can cause total production damage and depreciation of the final product. The study and development of new strategies for integrated anthracnose management can reduce the cost of production and consequently reduce environmental impacts. The objective of this work was to evaluate the efficiency of Trichoderma fungi in in vitro tests (antagonism, production of volatile and non-volatile compounds) for control of C. lindemuthianum and to evaluate the efficiency of endophytic fungi, salicylic acid, copper phosphite, acibenzolar-S-methyl (ASM) and fungicide for anthracnose control in greenhouse bean plants. Anthracnose was controlled in bean plants with the use of alternative products. The endophytic fungi Trichoderma viride and Trichoderma tomentosum inhibited C. lindemuthianum mycelial growth in the three in vitro tests. In greenhouse, T. viride, T. tomentosum, salicylic acid, ASM and fungicide were effective, but copper phosphite was not efficient in controlling anthracnose.

Beans (Phaseolus vulgaris) are one of the most important crops in human food, but the occurrence of disease can greatly reduce their productivity. The objective of this work was to evaluate the use of biotic and abiotic products to control angular spot (Pseudocercosporagriseola) in bean crop. Hight Roots® treatments; V6®; Wert Plus®, potassium phosphite; manganese phosphite; Copper phosphite, manganese, fungicide (fentin hydroxide), Ascophyllum nodosum, Bacillus subtilis and Bacillus thuringiensis, acibenzolar-S-methylic (ASM) and Trichoderma asperallum were used in greenhouse and field experiments with IPR Uirapuru cultivar. Biotic to abiotic products controlled angular leaf spot in bean plants. In greenhouse, the lowest values of Area Under the Disease Progress Curve (AUDPC) were obtained with fungicide application, A. nodosum, T. asperellum and copper phosphite, B. subtillis, acibenzolar-S-methyl, potassium phosphite, Hight Roots®, V6® and Wert Plus®. In field, in the first sowing season the treatments with fungicide, A. nodosum, B. thuringiensis and manganese resulted in lower AUDPC in relation to the other products. In the second sowing season, the tested products did not reduce the severity of the angular spot, since the productivity was higher for fungicide treatment. In the health quality of seeds, potentially pathogenic fungi such as Fusarium sp., Colletotrichum truncatum and Phomopsis sp., as well as the saprophytic fungus Aspergillus sp.

The occurrence of powdery mildew (Microsphaera diffusa) in soybean (Glycine max L.) has increased in the last harvests. In order to study the efficiency of powdery mildew control due to the application of alternative products and conventional fungicide, trials were conducted in Ponta Grossa, PR, Brazil, during the 2013/2014 and 2014/2015 growing seasons. The design used was randomized blocks with four replications. The treatments for the experiments were: 1 - control; 2 - acibenzolar-S-methyl (Bion 500 WG®); 3 - calcium (Max Fruit®); 4 - Micronutrients: copper, manganese and zinc (Wert Plus®); 5 - Micronutrients: manganese, zinc and molybdenum (V6®); 6 - NK fertilizer (Hight Roots®); 7 - Ascophyllum nodosum (Acadian®) and 8 - fungicide (azoxystrobin + cyproconazole) (Priori XTRA®) with the addition of the adjuvant. Four applications of alternative products (phenological stages V3, V6, R1 and R5.1) and two of fungicide (phenological stages R1 and R5.1) were carried out. The parameters evaluated were powdery mildew severity and productivity. The severity data made it possible to calculate the area under the disease progress curve (AUDPG). Alternative products didn’t reduce powdery mildew in the two harvests. The conventional fungicide treatment was the only one that controlled powdery mildew and didn’t reduce the productivity in both experiments.

Soybean mildew caused by Oomycota Peronospora manshurica, is a disease widely spread in Brazil. In order to study the efficiency of soybean mildew control due to the application of alternative products and fungicide in the field, experiments were conducted in Ponta Grossa, PR, Brazil, during the 2013/2014 and 2014/2015 growing seasons. The design used was randomized blocks with four replications. The treatments were: 1-witness; 2-acibenzolar-S-methyl; 3-calcium; 4-micronutrients: copper, manganese and zinc; 5-micronutrients: manganese, zinc and molybdenum; 6-NK fertilizer; 7-Ascophyllum nodosum and 8-azoxystrobin + cyproconazole with the addition of Nimbus adjuvant. Four applications of alternative products (phenological stages V3, V6, R1 and R5.1) and two of fungicide (phenological stages R1 and R5.1) were performed. The mildew severity was estimated using a diagrammatic scale. The severity data made it possible to calculate the area under the disease progress curve (AUDPC). In the 2014/2015 harvest the disease was more severe. The control of downy mildew by the use of fungicide did not reduce the epidemic. The fungicide was not efficient in the two evaluated seasons. All tested alternative products reduced the disease severity and AUDPC in both seasons. The best results in reducing downy mildew were found with the application of acibenzolar-S-methyl, micronutrients (Cu, Mn, Zn) and A. nodosum.

This study aimed to find an efficient method of inoculation of Stenocarpella maydis to produce white ear rot (WER) and estimate pathogen damage on maize grain yield components. Measured components were ear mass, grain mass per ear, and thousand grain weight. The experiments were performed in Ponta Grossa, PR, Brazil in a randomized block design with treatments arranged in a split plot with three replications. Three hybrids were studied. For each, five methods of inoculation in the ear at the soft dough stage were compared to un-inoculated controls. The ears were inoculated with 1 mL of the spore suspension (104 conidia/ml). Evaluations of the disease index (%), severity (%) and lesion area were performed in three (1st experiment) and four periods (2nd experiment), and the area under the disease progression curve was calculated for each of these periods. The area under the disease progression curve was calculated for each period. Inoculation at the center of the ear resulted in the best growth and development of the pathogen in both experiments. Inoculation at the base and center of the ears resulted in greater reductions in yield components, with degrees of damage varying from 27.8 to 43.1%. The inoculation of S. maydis in the center of the ear can be considered an appropriate method for resistance screening to WER in maize breeding programs. Key words: White ear rot, disease progress curve, severity, yield components.

Asian soybean rust (ASR) caused by Phakopsora pachyrhizi is the main soybean leaf disease in Brazil. Downy mildew (Peronospora manshurica) and powdery mildew (Microsphaera diffusa) are important soybean foliar diseases of occurrence in Paraná state. To reduce severity and yield losses caused by soybean foliar diseases, this work aimed to verify the efficacy of different application doses of the commercial product Dipel® Bacillus thuringiensis (Bt), which is a biological insect controller, combined with number of Opera® fungicide (pyraclostrobin + epoxiconazole) intercalated applications, and to investigate the effect of the Bt Dipel® in the resistance induction of soybean. For this study, different methodologies were used, including in vitro, in vivo and field assays. The results showed that Bt Dipel® can reduce soybean foliar diseases by inducing β-1,3 glucanase enzime and phytoalexin gliceolin. The fungicide application in the experiment condition reduced yield losses.

The goal of this study was to evaluate commercial sources of phosphite and acibenzolar-S-methyl (ASM) followed by one fungicide application on the control of downy mildew, powdery mildew and asian soybean rust, reducing the number of fungicide applications and increasing the control spectrum of these soybean diseases. Two field experiments were carried out in Ponta Grossa, Parana state, Brazil, during the 2006/07 and 2007/08 growing seasons. The experimental design was of randomized blocks with four replications. Treatments consisted on five sources of potassium phosphite and one of manganese (450 g P2O5 ha-1) and ASM (12.5 g a.i. ha-1) sprayed at the V7 and R2 stages. Phosphite- and ASM-treated plants received one application of the fungicide piraclostrobine + epoxiconazol (66.5 + 25 g i.a. ha-1) at the R3 stage and were compared to plants which received two fungicide applications at the R2 and R5.1 stages, as well as to untreated plants. The use of phosphite and ASM significantly reduced the AUDPC for downy mildew. No effects were observed for powdery mildew and Asian rust. The higher number of fungicide application increased the control of biotrophic fungi under higher disease pressure.

The objective of this study was to evaluate the effect of different sources of phosphite to control leaf rust, powdery mildew, yellow and brown spot in the wheat crop in Palmeira, Parana state, Brazil. The treatments were: four commercial sources of phosphites (A, B, C and D), applied at 1500 mL ha -1 , (applied in rate of active product) acibenzolar-S-methyl (ASM) at 500 mL ha -1 (isolad or association), pyraclostrobin + epoxiconazole (fungicide) at 400 mL ha -1 ) and phosphite A with pyraclostrobin + epoxiconazole (at 300 mL ha -1 ), phosphite A with pyraclostrobin + epoxiconazole (400 mL ha -1 ), acibenzolar-S-methyl with pyraclostrobin + epoxiconazole (400 mL ha -1 ) and control (water), . The experimental design adopted was complete randomized blocks with four replications. Regarding diseases, evaluations were done on the determination of severity and the calculation of the area below the curve of the disease progress in the flag leaf and entire plant. Leaf area index, thousand seeds weight, hectoliter weight and yield were also evaluated. Phosphite, independently source, did not act on leaf rust, powdery mildew, yellow and brown spot. The resistance inducer acibenzolar-S-methyl either isolated or associated to other fungicides affected leaf rust and powdery mildew of the wheat. Only phosphites associated to the fungicide controlled diseases, however there was no additional increase in yield whether compared to the control promoted by the fungicide.

O estado do Paraná contribui significativamente para o abastecimento de cebola no Brasil. Apesar disso, ainda não ocorre produção de sementes, o que demanda necessidade de pesquisa nessa área. Avaliou-se épocas de colheita e presença ou não de haste floral nas umbelas sobre o rendimento e potencial fisiológico de sementes de cebola. Os tratamentos resultaram da combinação de três épocas de colheita (com cápsulas ainda verdes, no início de abertura das cápsulas e com 10% de sementes expostas), combinadas com umbelas de haste floral com comprimento de 15 cm ou sem haste floral, arranjados em esquema fatorial 3x2. O delineamento experimental foi de blocos casualizados, com quatro repetições. Os bulbos da cultivar Crioula foram provenientes da EPAGRI (SC) e plantados em julho/2002, em Imbituva (PR), sob cultivo protegido de plástico de polietileno, usando estrutura modelo Londrina. Na fase de florescimento, quatro umbelas por parcela foram etiquetadas para as avaliações. Em cada uma das umbelas colhidas, foram separados e contados o número total de flores fecundadas (cápsulas) e de flores não fecundadas. As sementes foram retiradas das cápsulas e posteriormente contadas, obtendo-se o número total de sementes e de sementes por cápsula. Foram avaliadas a massa total de sementes por umbela, massa de 100 sementes e conduzidos os testes de germinação e vigor. A colheita das umbelas com haste de 15 cm não influiu no rendimento nem no potencial fisiológico das sementes. A época de colheita das umbelas influiu na quantidade e na qualidade das sementes. A colheita realizada no início de abertura das cápsulas ou com 10% de sementes expostas resultou em maior número de sementes por umbela, mais semente por cápsula, maior rendimento por umbela e maior massa de sementes. O rendimento médio foi de 2,9 g/umbela. Além disso, resultou em maior vigor e germinação (90,25% e 85,25%, respectivamente). Na prática, é desejável proceder-se à colheita das umbelas no início da abertura das cápsulas, para evitar perdas por degrana ou doenças. The Paraná State (Brazil) contributes significantly to the Brazilian onion production. However, this State imports all needed onion seeds. The effect of umbel's harvest period, and harvesting with or without the seed stalk were evaluated. Treatments resulted from the combination of three harvesting periods (with green capsules, at the beginning of capsule opening and with 10% opened capsules), combined with umbels on 15 cm long stalks or without stalks, arranged in a factorial scheme 3x2. The experimental design was a randomized blocks, with four replications. The bulbs of Crioula cultivar proceeded from EPAGRI, Santa Catarina State, and were planted on July/2002, in Imbituva, Paraná State, under protected cultivation. At flowering, four umbels per plot were marked to future use in the evaluations. The number of total of fertile flowers (capsules) and unfertile flowers were counted on each harvested umbel. Seeds were detached from capsules and the number of seeds per capsule obtained, besides the yield per umbel, weight of 100 seeds, germination and vigor of the seeds. Harvesting umbels with the seed stalk had no effect on the seed yield and on seed physiological potential. The harvesting period presented significant effect on the amount and quality of the harvested seeds. The best harvesting period was at the beginning of capsule opening or when 10% of capsules were opened, resulting in higher number of seeds/umbel, higher seed yield/umbel and higher seed weight per capsule. The average yield was 2.9 g/umbel besides higher vigor (90.25%) and germinability (85.25%). Harvesting at the beginning of capsule opening helps to avoid the lost of seeds by thresh or diseases.

Foram realizados experimentos em ambiente controlado, em câmaras de crescimento, com duas cultivares de feijoeiro (Phaseolus vulgaris), Rosinha e Carioca, para a quantificação de componentes monocíclicos da mancha angular. Os componentes monocíclicos avaliados foram: período de incubação, severidade da doença e taxa de crescimento das lesões, sob as temperaturas de 6, 10, 14, 17, 21, 25, 29 e 33 ºC. Nenhum sintoma da mancha angular ocorreu em 6 e 33 ºC. A severidade da mancha angular foi elevada na faixa de temperatura entre 20 e 25 ºC e o período de incubação foi favorecido pela temperatura de 25 ºC, para as duas cultivares testadas. Esta temperatura também proporcionou a maior taxa de crescimento das lesões e estes dados foram ajustados, em função da temperatura por uma equação do primeiro grau. O efeito do período de molhamento foliar (5, 6, 12, 18, 24, 30, 36, 42, 48 e 54 h) na severidade da doença também foi avaliado. A severidade da mancha angular do feijoeiro aumentou com o aumento da duração do molhamento foliar até o máximo de 54 h. As variações de severidade da mancha angular do feijoeiro, em relação ao número de horas de molhamento foliar, foram explicadas pelo modelo de Richards. A função Beta-Richards explicou o efeito combinado da temperatura e da duração do molhamento foliar na severidade da mancha angular do feijoeiro para ambas as cultivares. Monocyclic components of angular leaf spot, were quantified on two bean (Phaseolus vulgaris) cultivars Rosinha and Carioca in growth chambers. Incubation period, disease severity and lesion growth rate were assessed, at temperatures of 6, 10, 14, 17, 21, 25, 29 and 33 ºC. No angular leaf spot symptoms occurred at 6 and 29 ºC. Severity for angular leaf spot was high between temperatures of 20 and 25 ºC, and the incubation period for both varieties tested was favoured at a temperature of 25 ºC. This temperature also provided the greatest lesion growth rate and these data were adjusted by a first grade equation in function of the temperature. The effect of the leaf wetness duration (5, 6, 12, 18, 24, 30, 36, 42, 48 and 54 h) in the severity of disease symptoms was studied as well. Severity for the angular leaf spot increased with the wetness duration period to the maximum of 54 h tested. The variations of angular leaf spot in relation to the number of hours of leaf wetness were explained by the Richards model. The Beta-Richards function explained the combined effects of the temperature and leaf wetness duration in the severity of angular leaf spot, for both varieties.

O cultivo protegido com polipropileno ou agrotêxtil tem confirmado os seus benefícios no aumento do rendimento de várias hortaliças, quando utilizado como mecanismo de proteção de plantas, ou como na técnica de cobertura de solo. No entanto, pouco se conhece sobre a intensidade de doenças nos sistemas de cultivo utilizando estas técnicas. Nesse contexto, o presente trabalho buscou avaliar o efeito da cobertura do solo com polipropileno preto (gramatura de 40 g m-2) e de cobertura de plantas com polipropileno branco (gramatura de 25 g m-2) na intensidade de doenças no cultivo de “pak choi”. O polipropileno preto foi fixado sobre o solo antes do transplante das mudas e o branco, colocado sobre as plantas, como uma manta flutuante, após o transplante e fixado nas laterais com o próprio solo do canteiro. Cada parcela teve 24 plantas no espaçamento 0,25 x 0,25 m com mudas que foram transplantadas no estádio 4-5 folhas definitivas, obtidas de bandejas. Na colheita, avaliou-se a mancha de Alternaria, a podridão mole e a massa fresca da planta. O polipropileno branco na cobertura de plantas reduziu a porcentagem de folhas doentes e a severidade da mancha de Alternaria. Ademais, promoveu aumento na produtividade da variedade ‘Canton’, obtendo-se plantas com maior massa fresca. Não houve resposta significativa da cobertura do solo com polipropileno preto nas características de produção; no entanto, essa técnica deve ser considerada no manejo da cultura, propiciando menor incidência da podridão mole.

Th e downy mildew, caused by Peronospora manshurica , is a secondary disease in soybean culture, however in humid cold regions has occurred with more frequency. In this study a diagrammatic scale was developed and valided a diagramatic scale for to quantify the severity of the disease Peronospora manshurica in soybean. Of the 200 collected leaves in Castro (PR), were selected 100 leaves dissected dried herbarium in better conservation’s state with different levels of severity and after were numbered to determinate the lesion and leaf area to calculate the severity percentage per each leaf. The scale considered the minimum and maximum limits of severity observed in the field and the intermediate values followed logarithmic increments, obtaining eight levels: 0,08; 0,30; 1,10; 3,39; 12,85; 34,92; 66,13 e 87,65%. In validation seven appraisers raters , with and without previous practice estimated the lesion area before and after the use of the scale. Accuracy and precision were determined by linear regression, the results of accuracy and precision were satisfactory. The coefficient of determination values after the use of the scale demonstrated increase getting levels of 0,97, in relation to the error dispersion graphic, improved 100% of the cases, decreasing the number of the notes more then 10% of error of 16 for 8,2. With the Test F (Assistat program) was observed the statistic difference in R 2 when it was used the scale, which provided adequate and it will can be utilized to validated the severity in others experiments.

O cancro cítrico, causado por Xanthomonas axonopodis pv. citri (Xac), é um dos mais graves problemas fitossanitário da citricultura brasileira. Com a introdução da lagarta minadora dos citros (Phyllocnistis citrella [LMC]), houve um aumento drástico do número de focos do cancro cítrico, além da mudança do padrão espacial de fortemente agregado para moderadamente agregado e ao acaso. Foram avaliados: (1) suscetibilidade de três condições foliares: folha intacta, ferimento mecânico e injúria de LMC nas fases ovo, 1º ínstar, 3º ínstar e pupa, inoculados em diferentes concentrações de Xac (101, 102, 104 e 106 ufc/ml); (2) período de suscetibilidade da folha intacta, do ferimento mecânico e injúria de LMC inoculados a 106 ufc/ml; e (3) efeito da temperatura (12, 15, 20, 25, 30, 35, 40 e 42°C) e duração do molhamento foliar (0, 4, 8, 12, 16, 20 e 24 h) em folhas sem ferimento inoculadas a 106 ufc/ml. A concentração mínima de inóculo para causar sintomas da doença em folha intacta, injúria de LMC fase ovo e 1º ínstar foi de 104 ufc/ml; em ferimento mecânico e injúria de LMC fase 3º ínstar e pupa, 102 ufc/ml. Injúria da fase pupa resultou em grande severidade do que nos demais tratamentos a 106 ufc/ml (2 vezes maior do que em folha intacta).O período de suscetibilidade da injúria de LMC foi seis vezes mais longo do que do ferimento mecânico e a máxima suscetibilidade foi três vezes maior que em folha intacta. A LMC está relacionada com o aumento do dano que expõem mesofilo foliar à infecção direta de Xac, aumentando a suscetibilidade da folha por longo período. A faixa de temperatura ótima para o desenvolvimento do cancro cítrico foi de 25-35ºC. Entretanto, a severidade foi mais alta entre 30-35ºC. Sintomas de cancro não desenvolveram a 42ºC e na ausência de molhamento foliar. O efeito da temperatura foi maior do que a duração do molhamento foliar. A mínima duração de molhamento para infecção de Xac foi menor que 4 horas. Asiatic citrus canker, caused by X. axonopodispv.citri (Xac), is one of the most serious phytosanitary problems in Brazilian citrus crops.The introduction of the citrus leafminer (Phyllocnistis citrella [CLM]), has resulted in an increase in the number of disease foci and has changed the spatial pattern of citrus canker symptomatic trees from strong aggregation to intermediate aggregation and random patterns. We evaluated: (1) susceptibility of three distinct leaf condition: intact leaves, mechanical wounding, and injury caused by CLM at the egg stage, 1st instar, 3rd instar, and pupal stage, inoculated at different concentration of Xac (101, 102, 104, and 106 cfu/ml); (2) susceptibility period of intact leaves, mechanical wounding, and CLM injury inoculated at 106 ufc/ml; and (3) effect of temperature (12, 15, 20, 25, 30, 35, 40 and 42°C) and leaf wetness durations (0, 4, 8, 12, 16, 20, and 24 h) on unwounded leaves inoculated at 106 ufc/ml. The minimum inoculum concentration to cause symptom development in intact leaves, CLM injury at the egg stage and 1st instar was 104 cfu/ml; in mechanically wounded leaves and CLM injuries at the 3rd instar and pupa stage, 102 cfu/ml. The injuries from pupa stage resulted in greater disease severity than other treatments at 106 cfu/ml (two times higher than in the intact leaf). Susceptibility period of CLM injury was six time longer than mechanical wounding and maximum observed susceptibility was three times higher than intact leaf. CLM is related to the amount of damage that exposes mesophyll cells to direct Xac infection, increasing the susceptibility of leaf for long period. Optimal temperature for development of citrus canker was 25-35°C. However, disease severity was highest in the range 30-35°C. Symptoms did not develop at 42°C and zero hour of leaf wetness duration. Effect of temperature was .greater than leaf wetness duration. The minimum wetness duration for Xac infection was as short as 4 h.