Fumigation toxicity of allicin against three stored product pests

•The potential of allicin as a grain fumigant was investigated.•Higher allicin concentration reduced fumigation time and vice versa.•The presence of wheat affected allicin toxicity against several grain insects.•A constant percentage of allicin was sorbed by the fumigated wheat daily.

The fumigant toxicity of allicin against the adults, larvae and pupae of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae) and Cryptolestes ferrugineus (Stephens) (Coleoptera: Cucujidae) was investigated under laboratory conditions. Results showed that for 6 d exposure of adults of these three species to allicin, the LC50 was 0.38, 0.51 and 0.51 μL/L of air, respectively, and the corresponding LC99 values were 1.11, 8.40 and 2.18 μL/L of air, respectively. The LC50 for larvae was 0.11, 0.12 and 0.36 μL/L of air after only 3 d exposure, respectively, indicating that the larvae were much more sensitive to allicin than adults. The pupal emergence of T. castaneum, O. surinamensis and C. ferrugineus was reduced to 85.6, 94.4 and 100%, respectively, after allicin treatment with a concentration of 5 μL/L of air. Trials using allicin in containers filled to 50% of capacity with wheat to imitate commercial conditions resulted in LC99 values for 6 day exposure of 19.7, 32.1 and 26.9 μL/L of air for adults of the three species, respectively. Head space solid phase microextraction (HS-SPME) combined with gas chromatograph (GC) analysis indicated that the concentration of allicin (615 μL/L) in the sealed fumigation vessels decreased to 6.21 μL/L of air after 1 d fumigation and 1.54 μL/L of air after 6 d of fumigation in sealed bottles, respectively. The concentration of allicin decreased quickly as aeration times increased, with less than 0.05 μL/L of air after 16 d aeration regardless of the fumigation time. These results suggest that allicin may be suitable as an active ingredient in a botanical fumigant.