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Title: Treatment of pastures with diflubenzuron suppresses Horn Fly, Haematobia irritans (L.) (Diptera: Muscidae) development

item Lohmeyer, Kimberly - Kim

Submitted to: Journal of Agricultural and Urban Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2008
Publication Date: 4/1/2007
Citation: Tomberlin, J.K., Lohmeyer, K.H., Kattes, D. 2007. Treatment of pastures with diflubenzuron suppresses Horn Fly, Haematobia irritans (L.) (Diptera: Muscidae) development. Journal of Agricultural and Urban Entomology. 24(2): 95-101.

Interpretive Summary: Diflubenzuron is an insecticide commonly used in cattle pastures and rangelands to control grasshoppers and armyworms. There is no waiting period required before cattle can re-enter and feed on the treated pastures. Diflubenzuron has also been shown to be effective at controlling horn fly larvae in cattle manure. Studies over two years were conducted to determine if pastures treated with diflubenzuron for grasshopper control also showed significant impact on horn fly populations. The number of adult flies that emerged from manure in the treated pastures was significantly less than the number that emerged from manure from the control pastures at three days after treatment. In addition, pupae recovered from manure from the treated pastures had a higher percentage of deformity when compared to pupae from the control pastures for up to 17 days after treatment. Diflubenzuron used as a pasture spray does not appear to be a long lasting control measure for horn flies. However, if it is already being used for grasshopper control, a few days of horn fly reduction may be an additional benefit.

Technical Abstract: Diflubenzuron is an insect growth regulator labeled for application to pastures and rangeland to suppress grasshopper (Orthoptera: Acrididae) populations. Livestock are permitted access to land immediately after treatment. We hypothesized that the development and survivorship of horn fly Haematobia irritans (L.) larvae feeding on manure resulting from these animals would not be impacted due to the presence of diflubenzuron residue. Survivorship to the adult stage and percent pupae deformed were recorded for horn flies developing on manure samples from pastures treated with 59 ml/0.4 hectares. Samples ranged in age from three to 31 d post treatment. This study was replicated in 2004 and 2005. Results were highly variable between site and year. Adult emergence was significantly lower for manure from the treated versus the control sites for one sample taken from one site 3 d post treatment. Horn fly survivorship for treated and control sites for remaining samples were not significantly different; however, horn fly survivorship to the adult stage in 11 of 15 sample dates taken was lower in treated than the control manure samples. Accordingly, a significantly greater percentage of deformed pupae was recorded for samples from the treated than the control sites <17 d post treatment. Based on this study, our null hypothesis can be rejected. Using diflubenzeron to suppress pasture and range land pests can also have an impact on horn fly populations associated with cattle feeding in these pastures. However, care should be taken to apply adequate coverage of land to ensure appropriate diflubenzuron levels are consumed resulting in the suppression associated horn flies.