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.

Silverleaf whitefly (SLW, Bemisia tabaci MEAM1) and aphids are sap-sucking insects, which pose a serious threat to Australian cucurbit crops and the horticulture industry. Traditional chemical control for these insect pests is becoming less effective, and there is a need to search for alternative or supplementary methods. This study aimed to manipulate the habitat of pumpkin crops in a tropical setting (Queensland, Australia), by growing pumpkins (var. Japanese pumpkin) alone and between lablab (Lablab purpureus L. Sweet). It was hypothesized that the presence of lablab will increase the populations of natural enemies, and through their control of insect pests such as SLW and aphids, will affect pumpkin yield. The population of arthropods (natural enemies and pests of pumpkin), with a focus on SLW and aphids, were sampled weekly on both lablab and pumpkin crop for a total of 21 weeks. Results showed that lablab hosted more enemies of SLW per plant than pumpkin in either treatment. In addition, adult SLW numbers were significantly higher in the pumpkin-only crop compared with the pumpkin grown between lablab, while pumpkin in the mixed plantings had significantly more ladybirds and lacewing larvae (P < 0.05). While there was no significant difference in the average fruit weight between treatments, the total weight (kg) and number of marketable pumpkins per hectare was greater (P < 0.05) for the pumpkin/lablab treatment than the pumpkin-only treatment. This study shows that growing lablab alongside a pumpkin crop may enhance natural enemies of SLW and could significantly increase the yield.