Repellent effect of garlic against stored product pests

Intact garlic clove, grated garlic and its Volatile extract applied on brow n rice showed a repellent effect but no insecticidal activity against two s tored product pests, i.e. the maize weevil and the red flour beetle. Neithe r repellency nor insecticidal activity was observed with garlic or its extr act against two agricultural pests, diamondback moth larvae and green peach aphids. In comparative tests, hot pepper and "wasabi" mustard demonstrated only weak repellency, if any, although volatile components of "wasabi" mus tard showed insecticidal activity against these insects. Volatile component s of garlic were trapped and subjected to GC-MS analysis. Four major peaks resolved were sulfide compounds produced by the rapid degradation of allici n and a cyclic compound produced by dehydration. It remains to be determine d whether allicin itself, the degradation products, or the mixture of these are responsible for the repellent effect.