Infection by the semi-persistently transmitted Tomato chlorosis virus alters the biology and behaviour of Bemisia tabaci on two potato clones.

Insect-borne plant viruses usually alter the interactions between host plant and insect vector in ways conducive to their transmission ('host manipulation hypothesis'). Most studies have tested this hypothesis with persistently and non-persistently transmitted viruses, while few have examined semi-persistently transmitted viruses. The crinivirus Tomato chlorosis virus (ToCV) is semi-persistently transmitted virus by whiteflies, and has been recently reported infecting potato plants in Brazil, where Bemisia tabaci Middle East Asia Minor 1 (MEAM1) is a competent vector. We investigated how ToCV infection modifies the interaction between potato plants and B. tabaci in ways that increase the likelihood of ToCV transmission, in two clones, one susceptible ('Agata') and the other moderately resistant (Bach-4) to B. tabaci. Whiteflies alighted and laid more eggs on ToCV-infected plants than mock-inoculated plants of Bach-4. When non-viruliferous whiteflies were released on ToCV-infected plants near mock-inoculated plants, adults moved more intensely towards non-infected plants than in the reverse condition for both clones. Feeding on ToCV-infected plants reduced egg-incubation period in both clones, but the egg-adult cycle was similar for whiteflies fed on ToCV-infected and mock-inoculated plants. Our results demonstrated that ToCV infection in potato plants alters B. tabaci behaviour and development in distinct ways depending on the host clone, with potential implications for ToCV spread.

Influence of Trichomes in Strawberry Cultivars on the Feeding Behavior of Chaetosiphon fragaefolii (Cockerell) (Hemiptera: Aphididae).

Chaetosiphon fragaefolii (Cockerell) (Hemiptera: Aphididae) is the predominant aphid in strawberry (Fragaria × ananassa Duchesne) production systems in Brazil. This pest species directly damages the plants and is also responsible for spreading viruses. Further, C. fragaefolii often renders strawberry cultivation unviable, because of its high reproductive rate, as well as the large number of individuals generated through parthenogenesis. The present study aimed to (1) evaluate the feeding behavior of C. fragaefolii in four strawberry cultivars (Albion, Aromas, Camarosa, and San Andreas) and (2) identify the resistance factors associated with the number and type of trichomes in the cultivars, and also its effect on the feeding behavior of C. fragaefolii, using the electrical penetration graph (EPG) technique. The results revealed an intrinsic relationship between the number of trichomes on the cultivar and feeding behavior of C. fragaefolii. A higher number of trichomes, both tector and glandular, was observed in Albion compared to that of other cultivars, resulting in a longer no probing (Np) period per insect, and a longer Np phase. A relatively short phloem phase and ingestion time of the phloem sieve elements were also observed in Albion. These results suggest that the trichomes act as a physical barrier creating difficulties for C. fragaefolii to feed, thereby altering its feeding behavior in the four cultivars studied.

Evaluación del cultivo protegido por agrotextil en la cultura de lechuga y su desempeño en diferentes tipos de aplicaciones

RESUMEN El uso de cultivos protegidos con agrotextil es una técnica que se ha ido destacando a lo largo del tiempo, por su eficacia y facilidad de aplicación, principalmente en forma de cubiertas flotantes. El objetivo de este trabajo fue evaluar los diferentes métodos de aplicación del agrotextil blanco (17 g / m2) aplicado en forma de coberturas flotantes, asociadas a cubierturas de suelo utilizando agrotextil negro (45 g / m2) y mulching plástico negro (MP 25 µm) en el cultivo de lechuga. Los resultados mostraron variaciones significativas para masa fresca, lo que indica que el mejor método de aplicación fue en mulching plástico asociado al agrotextil en forma de cubierta flotante. El cultivo de lechuga mantenida sobre el agrotextil mostró un desarrollo vegetativo superior cuando se comparó en la parte aérea el número de hojas / planta y la altura, mostrando mejores resultados cuando se utilizó, en el tratamiento, la cobertura directamente sobre el cultivo o utilizando una guía de hilo de nylon como guía en comparación con el tratamiento sin cobertura agrotextil. Otro factor positivo fue el efecto de agrotextil como barrera física contra insectos plaga, reduciendo significativamente la infestación.

RESUMO A utilização do cultivo protegido com agrotextil é uma técnica que vem se destacando ao longo do tempo, por sua eficiência e facilidade de manejo, principalmente na forma de cobertura flutuante. O objetivo do presente trabalho foi avaliar os diferentes métodos de aplicação do agrotextil branco (17 g/m2) aplicado na forma de cobertas flutuantes, associado a coberturas de solo utilizando o agrotextil negro (45 g/m2) e o mulching plástico preto (MP 25 µm) na cultura de alface. Os resultados mostraram variações significativas quanto à massa fresca, indicando que o melhor método de aplicação se constituiu no mulching plástico associado ao agrotextil na forma de coberta flutuante. A cultura da alface mantida sobre o agrotextil mostrou um desenvolvimento vegetativo superior quando se comparou o número de folhas/planta e a altura da parte aérea, apresentando melhores resultados quando se utilizou, no tratamento, a cobertura diretamente sobre o cultivo ou empregando um fio guia quando comparados ao tratamento sem cobertura de agrotextil. Outro fator positivo foi o efeito do agrotextil como barreira física contra insetos-praga reduzindo significativamente a infestação.