Reducing whiteflies on cucumber using intercropping with less preferred vegetables

The effectiveness of four less preferred vegetables - celery, asparagus lettuce, Malabar spinach, and edible amaranth - were investigated for suppression of two biotypes of sweet potato whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) on cucumber, Cucumis sativus L. (Cucurbitaceae). Intercropping celery and Malabar spinach with cucumber significantly reduced whitefly numbers on cucumber. Y-tube olfactometer behavioral assays revealed that whiteflies were strongly repelled from the aqueous extracts of the less preferred vegetables. The level of whitefly repellency varied with combinations of intercropped vegetables, and also differed between the two whitefly biotypes. For whitefly biotype B, the greatest repellency was observed with asparagus lettuce extract, whereas celery and Malabar spinach extracts were more repellent to whitefly biotype Q. Two major volatile constituent compounds were identified, D-limonene from celery and geranyl nitrile from Malabar spinach. Sprayable 1% formulations of these compounds significantly reduced whitefly colonization on cucumber under field conditions.