Abstract
In recent years, there has been an increasing interest and need for alternatives to structural fumigations, and one alternative that has been used across the industry is aerosol insecticides. Previous tests inside a pilot-scale mill demonstrated that aerosol particle size, delivery method, and the spatial configuration of the mill all influenced effectiveness. However, there is no research conducted inside large commercial facilities. The objective of this research was to evaluate a pyrethrin-plus-methoprene aerosol application inside a commercial mill on adult Tribolium confusum Jacquelin duVal, confused flour beetle, directly exposed to the aerosol and residual effects on larvae. Additionally, five aerodynamic particle sizer spectrometers were placed in the facility and recorded instantaneous spray concentration and estimated aerosol deposition. Adult T. confusum exposed nearest to the aerosol application points had the highest percentage of affected adults (>60%). The aerosol also had vertical movement when released at the top of a three-story open room; instantaneous concentrations were recorded on the ground floor. The aerosol residual was highly effective after 6-weeks post aerosol exposure, as 80% of the bioassays did not have any adult emergence from exposed larvae. This research demonstrates a practical use of aerosol insecticides and their potential to be an effective alternative to structural fumigations.
Highlights
Methyl bromide has been used worldwide as a fumigant since the 1930s, but has been identified as an ozone-depleting agent under the Montreal Protocol, and its use as a structural fumigant for mills, processing plants, and warehouses is being phased out worldwide [1]
As the aerosol applications progressed from the first application to the last application, the number of affected T. confusum adults was reduced
This could indicate the amount of insecticide released differed between the first and last application point, either because the applicator opened the valve and released more product at the different locations, or that the tank was getting low and the release time was sufficient the amount of active ingredient left in the cylinder was insufficient to cause efficacy
Summary
Methyl bromide has been used worldwide as a fumigant since the 1930s, but has been identified as an ozone-depleting agent under the Montreal Protocol, and its use as a structural fumigant for mills, processing plants, and warehouses is being phased out worldwide [1]. There is an increased interest and need for alternatives to methyl bromide fumigations to manage stored product insects inside structures. Alternatives to methyl bromide include but are not limited to physical control methods, including heat or cold treatments; fumigant replacements such as phosphine or sulfuryl fluoride; contact insecticides such as cyfluthrin or deltamethrin; or aerosols insecticides such as pyrethrin with pyriproxyfen insect growth regulator (IGR) or pyrethrin with methoprene-IGR. Aerosol insecticides are a suspension of a liquid chemical compound held under pressure, and when the pressure is relieved the released particles become atomized and disperse throughout a space before settling onto surfaces. Insecticides applied as aerosols are dispensed into the air as particles that commonly range from 5–50 μm [2]. Aerosols are released from either a fixed dispensing system from overhead locations or from a portable cylinder or fogger and applied by Insects 2019, 10, 150; doi:10.3390/insects10050150 www.mdpi.com/journal/insects
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