|PAUDYAL, S - Oklahoma State University|
|OPIT, G - Oklahoma State University|
|BINGHAM, G - Vestergaard Frandsen Sa|
|GAUTAM, S - Oklahoma State University|
Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/25/2016
Publication Date: 6/7/2016
Publication URL: https://handle.nal.usda.gov/10113/63264
Citation: Paudyal, S., Opit, G.P., Arthur, F.H., Bingham, G.V., Gautam, S.G. 2016. Contact toxicity of deltamethrin against Tribolium castaneum (Coleoptera: Tenebrionidae), Sitophilus oryzae (Coleoptera: Curculionidae), and Rhyzopertha dominica (Coleoptera: Bostrichidae) adults. Journal of Economic Entomology. 109(4):1936-1942. doi:10.1093/jee.tow107.
Interpretive Summary: Insect pests are a major cause of postharvest losses experienced by smallholder farmers in developing countries, 30-80%, and are a major threat to food security. Insecticide impregnated fabric bags have potential to reduce loses by preventing insects from invading the bagged grain. Bags impregnated with the pyrethroid insecticide deltamethrin are commercially available (ZeroFly Storage , but there is little information on the time required for stored product insects to be incapacitated (knocked down) after exposure to deltamethrin, or if insects can recover after they are removed from a treated surface. Knockdown of adult red flour beetles, rice weevils, or lesser grain borers when exposed to different concentrations of deltamethrin was nearly 100% when exposed for 4 hours or less at concentrations greater than 25 ppm. Some recovery from knockdown occurred at concentrations less than 1,000 ppm after the insects were transferred to an untreated surface. Treated bags typically have a much higher concentration of deltamethrin (~3000 ppm), which suggests that the bags should be effective at incapacitating adult insects quickly, before they can penetrate through the bag to feed on the contents. Product managers can use these bags to help deter losses from insect pests in developing countries, and increase food safety and food security.
Technical Abstract: This study was conducted to evaluate deltamethrin-incorporated ZeroFly® Storage Bags for efficacy against stored-product insect pests. We evaluated response to deltamethrin concentrations for adults of three stored-product insects, Tribolium castaneum (Herbst), Sitophilus oryzae (L.), and Rhyzopertha dominica (F.). In insect toxicological studies, knockdown is the state of intoxication and partial paralysis as a result of exposure to an insecticide. Deltamethrin concentrations ranging from 1 to 3,000 ppm were sprayed on glass Petri dishes. After dishes dried, 20 adult insects of each species were placed on the treated dishes to determine the contact toxicity of deltamethrin. Assessments for knockdown were made at 15-min intervals for up to 8 h after initial exposure and then again after 24 or 48 h. Insects were then transferred to clean untreated Petri dishes with diet and observed from 0.5 to 72 h. Mortality was assessed 72 h after transfer to untreated dishes with food material. Deltamethrin was highly effective against all three species tested and achieved 99% knockdown of insects of all species within 4 h after exposure at concentrations = 25 ppm. Although some insects recovered from initial knockdown at concentrations = 1,000 ppm, nearly all the insects were killed at 3,000 ppm when exposed for 48 h. LC95 values for all species tested, for the 48-h exposure period, were ˜ 3,000 ppm, the concentration of deltamethrin present in the new ZeroFly Storage Bag fabric.