Vegetable oils have significant effects on several insect
pests of horticultural crops. Liu and Stansly (2000) showed
that cottonseed oil applied at 5 and 10 mL/L in a leaf-dipping
test produced toxic effects on second and third instars of the
silverleaf whitefly Bemisia argentifolii Bellows & Perring.
Martin-Lopez et al. (2006) also reported that vegetable oils
(rapeseed and soybean) sprayed at 10 mL/L on aphids Myzus
persicae (Sulzer) on pepper plants resulted in a high mortality
rate, about 70%. They suggested that the main mode of action
of the two vegetable oils against aphids was asphyxia, which
was caused by the covering of the insect body with a thin film
of oil. In addition, vegetable oils (peanut, cottonseed, castor,
soybean and sunflower) had a residual effect against the sweet
potato whitefly Bemisia tabaci (Gennadius), reducing adult
settling and oviposition (Fenigstein et al. 2001). Settling and
oviposition of the common greenhouse whitefly (Trialeurodes
vaporariorum Westwood) were also reduced by the application of pongam oil (Pavela & Herda 2007).