Effect of Cotton leaf curl virus infected plants on the biology of the whitefly,Bemisia tabaci (Hemiptera: Aleyrodidae): Vector–virus mutualism

Cotton leaf curl virus (CLCuV) (Geminiviridae : Begomovirus), the causative agent of leaf curl disease in cotton plants (Gossypium hirsutum), is exclusively transmitted by whitefly species Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). CLCuV transmission occurs in Sriganganagar (Rajasthan), an area endemic with cotton leaf curl disease. The relationships between plant viruses, their herbivore vectors and host plants can be beneficial, neutral, or antagonistic, depending on the species involved. To further understand these relationships, fecundity and life history parameters of an indigenous non- b (Asia II genetic group) biotype whitefly, B. tabaci, were compared on 10, 25, and 40 days post-inoculation (DPI), in CLCuV-infected and healthy cotton plants to determine the effect of virus on its vector. The development time of the immature stages of whiteflies was significantly reduced on CLCuV-infected plants. The development time of the immature stages did not change with severity of symptoms at 25 and 40 DPI (45- and 60-d-old plants). Cotton leaf curl virus infection increased percent egg viability of B. tabaci. Whiteflies deposited significantly fewer eggs on virus-infected plants than on healthy plants. Whiteflies had better egg viability on younger plants than older plants, whereas plant age did not affect the fecundity. Male and female whiteflies had shorter longevity on CLCuV-infected plants than on healthy plants.     

Effects on the aphid parasitoid <Emphasis Type="BoldItalic">Aphidius ervi</Emphasis> of an insecticide (Plenum<Superscript>®</Superscript>, pymetrozine) specific to plant-sucking insects

The use of a selective insecticide is highly recommended for Integrated Pest Management programs. Plenum (a.i.: pymetrozine; Syngenta Agro), a systemic insecticide, is regarded as a good candidate for use in situations where plant-sucking insects have to be controlled and where natural enemies can play a substantial role as biological control agents. In this context, the effects of Plenum on a host–endoparasitoid relationship were investigated. Potato aphids Macrosiphum euphorbiae were reared for 4 days on an artificial diet supplemented with a low concentration of Plenum (sublethal concentration inducing 15% aphid mortality) before parasitization by the endoparasitoid Aphidius ervi. The development of A. ervi larvae was negatively affected, especially during the early stages of development, and the sex ratio of the progeny was strongly male-biased. Moreover, the host-choice experiment showed that A. ervi was not able to discriminate between control and Plenum-contaminated aphids. These results show that Plenum may not be as selective as it was previously thought to be, and the observed effects need to be considered when developing IPM systems.     

Suppressive effect of acetylated glyceride (Bemidetach™EC) on <Emphasis Type="Italic">Tomato yellow leaf curl virus</Emphasis> transmitted by the whitefly <Emphasis Type="Italic">Bemisia tabaci</Emphasis> on greenhouse tomato plants

Acetylated glyceride (Bemidetach?EC)—a food additive—repels adult sweet potato whiteflies (Bemisia tabaci) and inhibits their mating behavior. We evaluated the effects of acetylated glyceride spraying of greenhouse-grown tomato plants on infestation with B. tabaci and the occurrence of Tomato yellow leaf curl virus (TYLCV) disease under commercial-like conditions. The abundance of adult B. tabaci was significantly reduced by three sprayings of acetylated glyceride, and the TYLCV incidence was significantly suppressed to less than 30% of that in the untreated control. These results suggest that acetylated glyceride sprays suppress the secondary spread of TYLCV in greenhouse-grown tomatoes by lessening B. tabaci adult density.