Insecticidal activities of garlic substances against adults of grain moth, Sitotroga cerealella (Lepidoptera: Gelechiidae)

The angoumois grain moth, Sitotroga cerealella (Olivier), is one of the most serious stored grain pests around the world. In attempts to reduce the losses caused by the moth and to suppress its populations, the fumigant activities, behavioral influence and ovipositional inhibition of garlic (Allium sativum) essential oil and its two major components, diallyl disulfide and diallyl trisulfide, were investigated against the adult grain moth. Their effects on reduction in survival of first instar larvae to adult emergence were also evaluated. Results showed that these three materials (garlic essential oil, diallyl disulfide and diallyl trisulfide) had significant fumigant activity with 50% lethal concentration values at 1.33, 0.99, and 1.02 mu L/L air space, respectively; meanwhile, the three materials possessed high behavioral deterrent activities against adults in the Y-tube olfactometer. When applied to rice grains, these materials reduced adult longevity and inhibited oviposition, with ovipositional inhibition above 70% at a concentration of 1.5 mu L/25 g in either no-choice or two-choice tests. In short, the study showed that both diallyl disulfide and diallyl trisulfide, like garlic essential oil, acted as fumigants, produced behavioral deterrence and inhibited oviposition against angoumois grain moth. Our work here indicates that diallyl disulfide and diallyl trisulfide may serve as potential alternatives for grain protectants since both of them can be prepared easily from readily available chemicals.