|Subramanyam, Bhadriraju -|
|Boina, Dhana Raj -|
Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 26, 2014
Publication Date: N/A
Interpretive Summary: Recently there has been increasing use of the insecticide dichlorvos as an aerosol to control stored-product insects inside mills, warehouses, and processing plants, but there is little new research regarding distribution and efficacy of dichlorvos in field sites. We conducted a study by placing test dishes of adult confused flour beetle and the pupal stage of the red flour beetle in open, obstructed, and concealed sites inside a flour mill. Dichlorvos dispersed throughout the individual floors of the mill killed almost all insects in the open and obstructed sites, and killed most of the insects in the concealed sites. However, dichlovos dissipated rapidly and gave little residual control. Results show that this insecticide will give immediate kill, but other insecticides may be needed for residual control.
Technical Abstract: The distribution, efficacy, and residual activity of dichlorvos applied as an aerosol to each of five floors of the Kansas State University pilot flour mill (9,968.8 m3 total volume) were evaluated based on responses of adults of the confused flour beetle, Tribolium confusum (Jacquelin du Val), and pupae of the red flour beetle, Tribolium castaneum (Herbst), during and after application. Dichlorvos was applied at the highest labeled rate of 0.35 g/m3 on each floor. Concrete treatment arenas with or without different life stages of the two species were placed in open, obstructed, and concealed mill locations during aerosol application. The latter two locations included arenas placed underneath pieces of equipment and within equipment, respectively. These arenas were brought to the laboratory after 24 h in the mill, and insects were immediately exposed on the arenas or on arenas aged for 24-h in a laboratory growth chamber at 28 ± 1 °C and 65 ± 5% r.h. Knockdown and mortality of T. confusum adults was 99-100% and mortality of T. castaneum pupae was 97-100% in open and obstructed mill locations, indicating uniform distribution of dichlorvos on each floor. In concealed locations, knockdown and mortality of T. confusum and T. castaneum was 85-94%, indicating effective dispersion of dichlorvos. Holding insects directly exposed to dichlorvos for an additional 24 h in the same arenas did not increase knockdown or mortality. Exposure to aged dichlorvos residues on concrete resulted in moderate to poor knockdown and/or mortality of Tribolium spp. suggesting loss of residual activity. Results show dichlorvos will give immediate kill of exposed insects but will not offer effective residual control.