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ARS Home » Plains Area » Manhattan, Kansas » Center for Grain and Animal Health Research » Stored Product Insect and Engineering Research » Research » Publications at this Location » Publication #307046
Title: Susceptibility of Tribolium confusum (Coleoptera: Tenebrionidae) to pyrethrin aerosol: effects of aerosol particle size, concentration, and exposure conditions

Author
item Arthur, Franklin
item Campbell, James - Jim
item DUCATTE, GERALD - Mri Global

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/22/2014
Publication Date: 12/1/2014
Citation: Arthur, F.H., Campbell, J.F., Ducatte, G.R. 2014. Susceptibility of Tribolium confusum (Coleoptera: Tenebrionidae) to pyrethrin aerosol: effects of aerosol particle size, concentration, and exposure conditions. Journal of Economic Entomology. 107(6):2239-2251. DOI: http://dx.doi.org/10.1603/ECI4296.

Interpretive Summary: Aerosol insecticides are being used as an alternative to the fumigant methyl bromide to control insects inside flour mills, but there is little information available on effectiveness of those aerosols when they are applied at different particle sizes. We conducted tests by exposing adult confused flour beetles for different time periods to pyrethrin aerosol applied at either 2 or 16 microns. After exposure, beetles were held in the arenas in which they were exposed or transferred to new arenas with and without flour. At 16 microns, all adults were knocked down by the aerosol and there was an effect of exposure time and transfer to untreated dishes with food on subsequent mortality. At 2 microns, there was no mortality due to the aerosol, even when concentration was increased by a factor of four. Results show that as the actual particle size applied decreases the effectiveness of aerosols may also decrease as well. Our results will enable industrial personnel who apply aerosols to adjust particle size of aerosols so that particles are dispensed at the size necessary to give maximum control of flour beetles inside mills.

Technical Abstract: A series of laboratory studies were conducted to assess effect of droplet size on efficacy of pyrethrin aerosol against adults of Tribolium confusum Jacqueline DuVal, the confused flour beetle. A vertical flow aerosol exposure chamber that generated a standardized particle size diameter was used for these trials. In the first experiments, adults were exposed in chamber for 2.5 to 45 min to aerosol dispensed at a volumetric median particle size diameter (VMD) of 16 µm, and then held in the arenas in which they were exposed or transferred to new arenas with or without a flour food source. All adults were initially knocked down when removed from the chamber. Recovery from knockdown decreased as exposure interval increased, but the presence of a food source enhanced recovery at the lower exposure intervals. In the second experiment, the aerosol was applied at a VMD of 2 µm and adults were exposed for between 5 to 75 min. Knockdown of adults was 10% or less when adults were removed from the chamber regardless of exposure time and afterward there was essentially complete recovery of adults. In the third and final experiment, the same 2-um VMD particle size and exposure times were used, but the concentration of aerosol was increased by about 4x compared to the previous experiment. In this test, initial knockdown was greater at the higher exposure intervals, but by 3 and 4 days post-treatment recovery was again essentially 100%. This is the first published test assessing the efficacy of specific aerosol particle sizes on a stored product insect. Results indicate that particle size was a more important factor in conferring toxicity than the actual concentration or number of aerosol particles.