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United States Department of Agriculture

Agricultural Research Service

Title: Efficacy of the Ivomec Sr Bolus for Control of Horn Flies (Diptera: Muscidae) on Cattle in South Texas

Authors
item Miller, John
item Davey, Ronald
item Oehler, Delbert - RETIRED - ARS
item Pound, Joe
item George, John

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 10, 2003
Publication Date: October 1, 2003
Citation: MILLER, J.A., DAVEY, R.B., OEHLER, D.D., POUND, J.M., GEORGE, J.E. EFFICACY OF THE IVOMEC SR BOLUS FOR CONTROL OF HORN FLIES (DIPTERA:MUSCIDAE) ON CATTLE IN SOUTH TEXAS. JOURNAL OF ECONOMIC ENTOMOLOGY. 2003. v. 96. p. 1608-1611.

Interpretive Summary: The Ivomec SR Bolus was introduced as a means of long-lasting control of internal parasites in cattle. The bolus also controls of several tick species on cattle. The current study was conducted to determine the efficacy and persistence of the commercial Ivomec SR Bolus on adult horn flies feeding on the blood from treated cattle and on larval horn flies breeding in the manure produced by these cattle. Two groups of 6 Hereford heifers were held on separate, buffel grass pastures at the Cattle Fever Tick Research Laboratory in Mission, TX. Cattle in one pasture were treated with a single Ivomec SR Bolus and those in the second pasture were untreated controls. The concentration of ivermectin in the serum of the treated cattle resulted <10% control of adult horn flies feeding on the blood. Larval horn flies in the manure of treated cattle were unable to develop to adulthood for 19 weeks following treatment. When the trial was repeated using 2 boluses per heifer, the ivermectin concentration in the serum of the treated cattle killed 96.2% and 81.2% of male and female adult horn flies for 17 weeks after treatment, respectively. From these studies, we conclude that a single Ivomec SR Bolus used as an anthelmintic treatment can be expected to provide significant control of immature horn flies in the manure, but not of adults feeding on treated cattle.

Technical Abstract: When Hereford heifers were treated with a single Ivomec SR Bolus, the concentration of ivermectin in the serum of the treated cattle reached a maximum of 8.8 + - 0.9 ppb at 2 wk post-treatment. The single bolus treatment resulted in less than 10% mortality of adult horn flies feeding on the blood of the treated animals over the 21 wk trial. Bioassays of the manure from treated cattle showed complete inhibition of development of immature horn flies through wk 19 post- treatment. When the trial was repeated using 2 Ivomec SR Boluses/heifer, the concentration of ivermectin in the serum of the treated cattle reached a maximum level of 31.2 + - 3.9 ppb at week 13 post-treatment. The use of 2 boluses/heifer resulted in 96.2% and 81.2% mortality of adult male and female horn flies feeding on the blood of the treated animals, respectively. From these studies, we conclude that a single Ivomec SR Bolus used as an anthelmintic treatment can be expected to provide significant control of immature horn flies developing in the manure, but not of adults feeding on the treated cattle.

Last Modified: 11/27/2014
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