Title: The biological effect of cage design corrected for reductions in spray penetration Authors
Submitted to: Journal of Plant Protection Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 7, 2014
Publication Date: December 20, 2014
Citation: Fritz, B.K., Hoffmann, W.C., Bonds, J., Haas, K., Zbigniew, C. 2014. The biological effect of cage design corrected for reductions in spray penetration. Journal of Plant Protection Research. 54(4):395-400. Interpretive Summary: Assessing the effectiveness of adult mosquito control applications often depends on the observed impact of caged insects in the field. However, these cages act as filters for spray material being presented to the mosquito which result in overestimating actual exposure levels. A series of controlled wind tunnel studies were conducted to examine the effects of the bioassay cage on mortality with correction factors developed to estimate actual spray dosage levels impacting mosquitos. Estimated actual spray dosage levels were highly correlated to mosquito mortalities with actual toxic dosage levels being half that seen from uncorrected data. The developed methodology greatly enhances field assessment data which will result in better operational guidance to applicators and mosquito control districts.
Technical Abstract: In-field measures of physical spray concentration do not tend to correlate well with caged insect mortality data. It is postulated that filtration of the spray due to the structure of the cage is one of the causes of this inconsistency. Wind tunnel studies were conducted to investigate the accuracy of calculations developed to correct for filtration levels in cage mosquito bioassays. Zenivex E20 (Etofenprox) was applied at rates ranging from an LD 10 to an LD 90 to three cage types with significantly different filtration levels. The dose approaching the cage was converted to a dose entering the cage using cage penetration data from previous research. The filtration conversion factor returned a data set that directly correlated dose with mosquito mortality (R2 0.918). The percent mortality was a function of dose within the cage which was regulated by mesh type. Although the conversion factor was effective, the differences between cages was not always significant due the within group variation.