The whitefly Bemisia tabaci transmits the Pepper yellow leaf curl Indonesia virus to chili plants treated with low-risk insecticides

Abstract

Pepper yellow leaf curl Indovnesia virus (PepYLCIV) is a damaging disease of chili that can cause total yield loss. The sweet potato whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae), persistently transmits the virus. The insect can also directly damage chili plants by sucking their sap. The study was conducted to determine the effects of inoculation pressure, insecticide dosage, and application timing on whitefly populations and the incidence and severity of PepYLCIV. The results showed that higher inoculation pressures caused increased whitefly survival rates and viral disease transmission. The efficacy of azadirachtin was found to be dose-dependent, with higher concentrations being more effective in reducing both whitefly survival and virus transmission. In contrast, imidacloprid demonstrated higher efficacy across all tested concentrations, eliminating whiteflies and preventing virus transmission. The timing of insecticide application is a crucial factor influencing vector survival and disease incidence. Longer intervals between application and the inoculation access period (IAP) resulted in diminished efficacy of the insecticides. Azadirachtin and imidacloprid provided effective protection against PepYLCIV for up to 2 and 10 days post-application, respectively. Imidacloprid was effective for immediate vector control, while azadirachtin is effective at higher concentrations. Applying imidacloprid at the action threshold level could rapidly reduce the insect population, followed by azadirachtin application to maintain low population levels. The study results could be incorporated into an integrated management strategy to extend imidacloprid's efficacy against B. tabaci and concomitantly reduce its potential impacts on the environment and non-target organisms.