Fitopatologia

The aim of this study was to evaluate the infestation of whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) biotype B in 19 soybean cultivars in the Paragominas grain pole, 2017/18 crop year. The cultivars selected for planting are based on those normally planted in the Paragominas grain complex and research institutions. The sampling of the incidence of B. tabaci biotype B started on the 7th day after plant emergence (DAE), and the number of eggs, nymphs and adults was recorded weekly, that is, 10 small leaves of the plant evaluated in each plot, until the end of the crop cycle. The number of eggs and nymphs of B. tabaci type B was recorded in the laboratory with the aid of a stereoscopic microscope and adults made in loco. The values obtained were transformed into (x + 0.5)1/2, for normalization of these and submitted to analysis of variance (ANOVA) by the F test (Fisher). Tukey at 5% probability. The cultivar M 8644 IPRO showed the lowest infestation of eggs of B. tabaci and RK 6813RR was the most infested; for nymphs, the highest infestation was observed in cultivar RK 6813RR while in BRS 9383 IPRO there was less infestation; the highest number of whitefly adults was observed in the cultivar P 99R03, and M 8808 had the lowest average of adult insects and the period of highest incidence of whitefly was in the egg stage, in the first seven days after emergence (DAE); the period of 7 DAE was the most infested by adults and whitefly eggs; 35 and 42 DAE more infested by pest nymphs; meteorological factors mean temperature, rainfall and relative humidity do not showed influence on whitefly infestation, and relative humidity explained only 35.59% for incidence of eggs in soybean and the occurrence of adults explained 81% for the same parameter (eggs).

GM (genetically modified) corn with the CrylAb, mCry3A and Vip3Aa20 protein of Bt (Bacillus thuringiensis) and its respective isoline as control with and without chemical control for corn earworm were used in this research. Fusarium corncob damage was lower on GM corn with (12.5%) and without (25.7%) insecticide treatment as compared with the isoline that had 48.3% and 83.1% of damaged corncobs with and without chemical control, respectively. Corn smut cob damage was also lower on GM corn with (3.2%) and without (6.3%) insect control compared with 15.5% and 49.7% damage with and without insecticide treatment, respectively. Fusarium sp. corncob rot was also lower on GM corn with 5.7% and 9.5% whereas a 24.6% and 63% rot was observed on the isoline with and without insecticide control, respectively. Ustilago maydis severity was also lower on Bt corn finding 0.07% and 0.25% damage on treatments with and without insect control as compared with the isoline that showed an 11.6% and a 41.4% smut rot with and without insecticide treatment, respectively. The authors conclude that GM corn resistant to Helicoverpa zea prevents damage by the pest, eliminating the entrance pathway for Fusarium sp. and Ustilago maydis.

Ensayo: Amarillamiento letal del coco en Honduras Presentado por: Derick Ariel Jiménez sección B El presente documento contiene información sobre la enfermedad del Amarillamiento Letal del Cocotero ocasionado por un fitoplasma. se dice que los primeros registros de una enfermedad con síntomas similares al amarillamiento letal provienen desde inicios del Siglo XIX en las islas occidentales del Caribe. La enfermedad fue examinada como tal en Florida en 1950, en Jamaica en los años 60 y luego en la región de Miami en 1971. La enfermedad actualmente se encuentra esparcida en ciertos países tales como el Caribe (Jamaica, Gran Caimán, Cuba, República Dominicana, Haití, Bahamas), México, Belice, Estados Unidos (Florida y Texas), y que más recientemente en Honduras y Guatemala. La epidemia ha destruido más del 90% de la población de palma de coco (Cocos nucifera) de la variedad alta en la zona atlántica hondureña desde 1995. Este patógeno del Amarillamiento Letal del Cocotero la dispersión ocurre a través de dos formas. Uno es mediante la localización de una palma infectada es decir la enfermedad aparece en una o dos plantas y de ahí se extiende normalmente al azar a las siguientes palmas de una forma contigua. La segunda forma es por salto es de hasta decenas de kilómetros y donde son favorecidos por vientos fuertes como huracanes. Por lo tanto en estudios que se han realizado por algunas organizaciones, universidades tales coso como el zamorano en Honduras demuestran que la enfermedad se puede mover hasta 100 Km cada año, como ha ocurrido en ciertos países como México y Centro América (Honduras). Prosiguiendo con los síntomas que presenta en la variedad del cocotero alto del atlántico, como primer síntoma es normalmente la caída de los frutos en todos los estados de desarrollo. Prosiguiendo con la necrosis en las inflorescencias pero sin cubrirla por completo puede, pero con el transcurso del tiempo toda la inflorescencia aparece necrótica. Luego, las hojas toman una coloración amarillenta que empiezan por las más viejas y prosiguiendo hacia las más jóvenes. De esa forma lleva a que las hojas afectadas se sequen, donde toman una coloración café claro y que permanecen colgando del tronco por algún tiempo. Y como fase final ocasionando daños cerca de lo que es el cogollo dándole muerte y pudrición, ocasionándole la caída de la corana de las hojas, quedando únicamente el tronco en pie. Continuando con el agente causal y vector que es un nematodo (viroide). Estos organismos son localizados principalmente en la sabia (floema) donde ocurren en las áreas del cogollo (zonna meristematica), para retroregibersar estos síntomas en las palmas infectadas con el amarilla miento letal han utilizado lo que son tetraciclinas. En América, el vector del organismo causal ha sido identificado como Myndus crudus, hasta los momentos es el único vector. Este insecto adquiere el viroide durante su alimentación en las palmas infectadas. Para que estos insectos pasen a alimentarse del follaje de las palmas, primero cuando están en su etapa inmadura viven en comunión o asociadas en varias gramíneas hasta alcanzar su madures pasan a alimentarse del follaje de las palmas. El impacto de esta enfermedad en Honduras ha causado aspectos sociales, económicos y ambientales. En diversas comunidades étnicas de la zona costera de Honduras, la pérdida de las palmas de coco han ocasionado un grave problema ya que estos grupos dependen de ellas en gran manera ya sea para subsistencia, alimentación y otros. En Honduras las exportaciones de coco como fruta fresca, y la muerte de estas palmas por Amarillamiento Letal del Cocotero representa una pérdida a las industrias. De la misma forma también se ve afectado nuestro medio ambiente por esta

A produção de couves em geral tem sido severamente impactada pela doença conhecida como hérnia das crucíferas. Este problema se agrava pelas dificuldades encontradas pelos produtores para conseguir manter a produção de brássicas em áreas já contaminadas pelo patógeno, haja vista as dificuldades no controle da doença. Como se trata de patógeno com capacidade de sobrevivência por longos períodos no solo, medidas de caráter preventivo são fundamentais. Em áreas onde o patógeno já está presente, práticas de manejo do solo e das lavouras devem ser adotadas para se reduzir a multiplicação e a dispersão do patógeno e reduzir as perdas causadas pela doença. Maior sucesso pode ser obtido com a adoção coordenada de diferentes práticas de manejo pelo produtor individualmente e pelo conjunto de produtores de uma mesma localidade ou região. As medidas devem se voltar não apenas ao controle da doença, mas também à melhoria da conservação e das condições da fertilidade do solo, bem como do desenvolvimento das plantas.

Citrus Sudden Death (CSD) affects sweet oranges (Citrus sinensis) and some mandarins (Citrus reticulata) grafted on Rangpur lime (Citrus limonia) in the northern region of the State of São Paulo and south of the Triângulo Mineiro, Brazil. The progress of the disease in these groves is of great concern to citrus agribusiness. To characterize and quantify the damage caused by CSD, fruit yield (total weight and fruit number by plant, and fruit size) was assessed in four blocks for each combination of sweet orange varieties ('Hamlin', 'Pêra', 'Natal', and 'Valência') and class of age (three to five years, six to ten years, and 11 to 15 years). In each block, trees were classified according to CSD severity (0 = healthy, 1 = initial symptoms, and 2 = severe symptoms). For each severity level, ten trees were selected at random and harvested. Damage was characterized by reduction of total weight of harvested fruit per plant (28% and 50% for level 1 and 2, respectively), total number of fruit per plant (12% and 26% for level 1 and 2, respectively), and fruit size (22% and 41% for level 1 and 2, respectively). There was no difference in percentage of reduction of all evaluated variables of fruit yield among the tested sweet orange varieties. The youngest plants showed a higher reduction in fruit number per plant, while plants older than five years showed a higher reduction in fruit size. There was no difference in percentage of reduction of total weight of fruit per plant among plants of different age classes.

Los hongos endófitos, son aquellos que colonizan los tejidos vivos internos de las plantas sin causar efecto significativo en el hospedante. Estos hongos, al ejercer en ocasiones, antagonismo frente a patógenos fúngicos a la planta hospedante, pueden ser una solución para el control de muchas de las enfermedades forestales causadas por otros hongos. Este campo ha sido poco evaluado en pruebas in vitro y en pruebas en vivo. Se utilizaron cinco hongos endófitos y seis hongos patógenos que se enfrentaron en medio de cultivo generalista Papa + Dextrosa +Agar (PDA) en condiciones de oscuridad a 25º C por siete días. Durante este periodo se midieron los ejes centrales y laterales de la colonia. Con estos datos se obtuvo el coeficiente de forma del hongo y se calculó el crecimiento directo, el coeficiente de forma del hongo patógeno frente al endófito respectivo, el porcentaje de inhibición del crecimiento radial y el porcentaje de inhibición de la zona de crecimiento. Se establecieron placas únicamente con el hongo patógeno a manera de grupo control. Los datos se analizaron con un Análisis de Varianza y para los casos estadísticamente significativos se aplicó la prueba de Diferencia Mínima Significativa. Los resultados muestran que los endófitos que tienen una mayor inhibición frente a los hongos patógenos. De esta manera se demuestra un efecto controlador de al menos un endófito sobre uno o más patógenos. Esto sugiere su posible utilidad como Agente de Control Biológico (ACB) ante enfermedades forestales. La reducción del crecimiento de los hongos patógenos ante la presencia de los endófitos, puede deberse a los mecanismos de acción de éstos (competencia y secreción de micotoxinas) frente al patógeno. Se deben realizar ensayos in vivo donde los endófitos se inoculen de acuerdo con su ecología y con un tiempo adecuado para la colonización de la planta

To detect the presence of the bacterium Leifsonia xyli subsp. xyli (Lxx) in propagation material is important for the control of the ratoon stunting disease. The objective of this work was to improve a serological method for detection of the pathogen and to evaluate the policlonal antiserum specificity produced against Lxx. The antigen was prepared by resuspending pure culture in PBS and dialyzing it in glutaraldehyde 2% in PBS. The immunization schedule in rabbit constituted of two intramuscularly injections of 1:1 mixture of the antigen: Freund adjuvant (complete and incomplete, with interval of 21 days) and two subcutaneous injections of the antigen, with ten-day intervals. The antiserum was tested by Dot Blot and revealed by peroxidase to determine: (i) title of the antibody, (ii) reaction and specificity against Lxx, Xanthomonas axonopodis pv. vesicatoria and endophytic sugarcane (Saccharum sp.) bacteria (Azospirillum brasilense, A. lipoferum, Hebaspirillum rubrisubalbicans, H. seropedicae, Gluconacetobacter diazotrophicus). The highest dilution of antiserum (1:20.000) presented strong positive reaction and high specificity against Lxx. The purification of the IgG fraction did not improve the antiserum reactivity and specificity. In bacterial cell suspension the level of detection was estimated in 2x106 cells/ml.

Witches' broom has been considered the most important cocoa disease in Brazil since its first outbreak in Bahia in 1989. The objective of this work was to evaluate the disease progress curve and the gradient of witches' broom based on symptoms on flushes and pods of cocoa. The experiment was carried out in Uruçuca, southeast of Bahia State, in an area of grafted cocoa trees with 16 different genotypes, at an age of approximately three years after grafting, from September 2001 to July 2002. Assessments of symptomatic branches and pods were done monthly. Three treatments were used: (i) phytosanitation at six-monthly interval, (ii) monthly phytosanitation and (iii) monthly phytosanitation plus monthly fungicide application (cuprous oxide at a dose of 3g of a.i./plant/application). An adjacent area with abandoned cocoa trees showing high disease incidence was considered the main source of inoculum. In the temporal analysis, the monomolecular growth model was fitted to data and disease progress rates and determination coefficients were compared. A good fit for vegetative brooms and diseased pods was obtained with the monomolecular model. The final disease incidence in vegetative brooms and pods in the treatment that included the fungicide application was approximately five times lower than in the other treatments. Spatial analysis showed no evidence for a disease gradient. These results showed that the integration of cultural, chemical and genetic control methods allows a slower disease progress and lower final incidence of the disease.

Introduction Lettuce (Lactuca sativa) is an Asian vegetable introduced into Brazil through the Portuguese. Nowadays, it is the most appreciated vegetable in the country where its cultivation reaches a high level of technology, comprising green house, hydroponic and organic cultivation (Filgueira, 2000). Hydroponics is an alternative growing method that allows a relatively high number of plants per area at short time intervals. Although a reduction of disease incidence was thought to be expected on hydroponic lettuce, the presence of virus-like diseases has also been noted in several growing regions in São Paulo State. Lettuce diseases constitute a great problem, since they usually affect leaves, and viruses are especially harmful to commercial lettuce. In Brazil, the first report of Tospovirus in lettuce was made by Costa and Forster (1938), and later by Chagas (1970). At that time, this disease was known as Tomato spotted wilt virus (Ie, 1970) and sporadically found on lettuce. But...