Altered Behavioural Response of Whitefly (Bemisia tabaci) on Tomato Associated with Biocontrol Plants.

The whitefly, Bemisia tabaci, is a significant pest in tomato production, causing extensive damage and economic losses. In pursuing sustainable pest management strategies, this study investigates the deterrent effects of Tagetes species (T. erecta, T. patula, and T. minuta) and Crotalaria juncea on B. tabaci settlement and oviposition on tomato plants. Two free dual-choice experimental setups were conducted in a climate-controlled chamber. The study confirmed the efficacy of the experimental setup, with similar B. tabaci dispersion and oviposition on the sides with tomato plants alone. When Tagetes or C. juncea was introduced, a significant reduction in B. tabaci settlement and oviposition was observed compared to the tomato control side. To identify the modes of action of the companion plants on B. tabaci, a follow-up experiment, modifying the spatial arrangement of the plants, was set up to discriminate between physical barrier and chemical repellent effects. The findings suggest a potential crossing between repellence and barrier effects for Tagetes species when C. juncea acted as a sinkhole, trapping the whiteflies. A DHS-ATD-GC-MS analysis revealed that the repellent effect seems more associated with the composition than the intensity of the blend. Some already known repellent volatile compounds of Tagetes, such as limonene, were identified, but the major ketone compounds must also be tested. This study demonstrates the effectiveness of Tagetes and Crotalaria species as biocontrol plants in pest management for tomato production. These plants reduce pest pressure and support sustainable agriculture, offering an alternative to chemical pesticides. Further research should investigate mechanisms, field applications, and broader agroecological benefits.