Effect of allylisothiocyanate on Sitophilus oryzae, Tribolium confusum and Plodia interpunctella: Toxicity and effect on insect mitochondria

Allylisothiocyanate is a volatile chemical used for insect fumigation. Because its mode of action is not fully understood, the insecticidal efficacy of AITC was investigated using dry and wet-table applications on the major stored-product insects Sitophilus oryzae (L), Plodia interpunctella (Hubner), and Tribolium confusum Jacquelin Du Val. The LC50 values 72 h after fumigation with AITC against S. oryzae adults, P. interpunctella larvae, T. confusum adults and T. confusum larvae were 2.0, 2.2, 3.7, and 4.7[mu]l L-1 air, respectively. The complete mortality (100%) of all four insect pests was recorded after a 72-h exposure to AITC fumes at an atmospheric concentration of 11.5 [mu]l L-1 air, with results similar to those found with insects exposed to a recommended 5 mg L-1 dose of phosphine. No differences were detected between the effects of AITC and PH3 on the morphology of mitochondria taken from the midgut and integument epithelial cells of treated T confusum 3rd instar larvae. Rarefaction and vacuolization of the mitochondrial matrix were evident. The quantity of cristae and density of the electron matrix were also reduced. AITC has potential as a biodegradable and safe insect fumigant. The mitochondria alteration confirms the insecticidal effect of AITC, which may act on the respiratory system. (C) 2011 Elsevier Ltd. All rights reserved.