The effect of labiate herbs and white clover on Plutella xylostella oviposition.

Small-scale greenhouse intercrop experiments were carried out, with Brussels sprouts (Brassica oleracea gemmifera L.) as crop plants and the herbs sage (Salvia officinalis L.) and thyme (Thymus vulgaris L.) as intercrops. Significant reductions in diamond-back moth (Plutella xylostella (L.)) oviposition were observed on intercropped brassicas.

Green polyethylene models were shown to simulate the effect of the herbs. Contrast was shown to have no effect on oviposition by the diamond-back moth.

An intercrop of white clover (Trifolium repens L.) vs. an intercrop of thyme, resulted in significantly lower egg-loads on brassicas associated with clover. An olfactory effect is postulated to account for this difference.