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Residual efficacy of deltamethrin and β–cyfluthrin against Trogoderma variabile and Trogoderma inclusum (Coleoptera: Dermestidae)

Mukti N. Ghimire, Frank H. Arthur, Scott W. Myers, Thomas W. Phillips
Journal of stored products research 2016 v.66 pp. 6-11
Trogoderma granarium, Trogoderma variabile, active ingredients, adults, bioassays, concrete, cyfluthrin, deltamethrin, exposure duration, insect control, insecticide residues, insecticide resistance, larvae, mortality, pyrethrins, storage pests, stored products, toxicity
Trogroderma variabile Ballion, warehouse beetle, and Trogoderma inclusum LeConte, larger cabinet beetle, are dermestid pests of stored products. A series of laboratory bioassays were conducted to evaluate residual toxicity of the pyrethroids β-cyfluthrin and deltamethrin, applied on a concrete surface substrate for control of adults and larvae and adults of both species, to provide initial baseline susceptibility data for dermestids. Commercial formulations were applied at calculated deposition rates of 8, 16, and 24 mg active ingredient [AI] m(2) for deltamethrin and 10 and 20 mg active ingredient [AI] per m(2) for β-cyfluthrin. Ten adults or larvae of either species were introduced to an individual untreated and treated arenas at 0, 0.5, 1, 2, and 3 mo. post-treatment. Adult mortality was evaluated after 4 d of exposure with no food provided, and larval mortality was assessed 30 d after exposure with provision of food. Adult mortality of both species exposed to both insecticides ranged from 72.4 ± 6.9 to 100% depending on exposure interval. Larval mortality ranged from 18.3 ± 5.4 to 96.7 ± 2.1% on arenas treated with deltamethrin, and was significantly lower than adult mortality (P < 0.001) at bioassays conducted at 2 and 3 mo. post-treatment for both species at all three rates. Larval mortality on arenas treated with for β-cyfluthrin ranged from 20.0 ± 4.5 to 71.7 ± 4.8%, and was always lower (P < 0.001) at all exposure times at both rates for both species. There were only 4 out of a possible 20 comparisons with a significant difference (P < 0.05) between the three rates of deltamethrin and no occasions where there was a significant difference in mortality between the two rates of β-cyfluthrin. There were 3 occasions where mortality of T. inclusum adults or larvae was greater than T. variabile, and 1 occasion with the reverse, for exposures with deltamethrin. Results show larvae of both species were more tolerant than adults, and larvae could be used as an indicator stage for future studies of insecticidal susceptibility of Dermestids.