The presence of flour affects the efficacy of aerosolized insecticides used to treat the red flour beetle, Tribolium castaneum

Authors: TOEWS, MICHAEL - University Of Georgia; Campbell, James - Jim; Arthur, Franklin

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2010
Publication Date: 11/10/2010
Citation: Toews, M.D., Campbell, J.F., Arthur, F.H. 2010. The presence of flour affects the efficacy of aerosolized insecticides used to treat the red flour beetle, Tribolium castaneum. Journal of Insect Science. 10:196. Available online: www.insectscience.org\10.196.

Interpretive Summary: Stored product insect infestation in food processing facilities and storage warehouses is a serious problem and pest management professionals have begun using aerosolized insecticide applications more frequently to mitigate these infestations, although limited information is available on their efficacy. Pilot-scale tests were conducted to determine the effects of two aerosolized insecticides (pyrethrins and esfenvalerate), presence of food, and whether insects were out in the open or sheltered under pallets on all life stages of the red flour beetle. Insect mortality generally decreased as the amount of food (flour) increased, but mortality did not exceed 60% regardless of life stage with 2 grams of flour present. Mortality never exceeded 75% when insects were under pallets, but was never less than 80% when insects were in the open. Because differences in beetle mortality between insecticides were considerably less than differences attributed to amount of food present, this study suggests that sanitation and removal of obstructions prior to aerosol insecticide treatments was more important than choice of a particular insecticide.

Technical Abstract: Experiments were conducted in tightly sealed pilot-scale warehouses to assess the efficacy of common aerosolized insecticides on all life stages of Tribolium castaneum when exposed in dishes containing 0 to 2 g of wheat flour either under pallets or out in the open. Petri dishes containing 0, 0.1, 1, or 2 g of flour were prepared with 25 eggs, 3rd instars, pupae, or adults and then immediately treated with aerosolized solvent, pyrethrins, or esfenvalerate. Twenty-four h after insecticide exposure, the dishes were brought to the laboratory and placed in a growth chamber and held for a 3 d moribund (knockdown) assessment and a 21 d mortality assessment. Mortality in untreated controls was generally less than 10%, with the exception of the 21-d counts of adults and eggs. Solvent-treated replications followed similar trends, except that additional mortality was observed in exposed larvae and pupae. In the insecticide-treated dishes, mortality of T. castaneum provisioned with flour generally showed a linear decrease with increasing flour deposits. Regardless of life stage, mortality did not exceed 60% when individuals were exposed in petri dishes containing 2 g of flour. Exposure location also made a significant difference in observed mortality. While mortality never exceeded 75% in dishes positioned under pallets, there was never less than 80% mortality in dishes exposed in the open. Although there was a perceptible increase in mortality with esfenvalerate compared to pyrethrins, these differences were considerably less than the variation observed among flour deposits. The study suggests that sanitation and preparation prior to aerosol insecticide treatments were more important than choice of a particular insecticide.