CEFS Dairy Unit Develops “CowVac” to Control Horn Flies Without Insecticides

The horn fly is the southern US’ most serious cattle pest. This small biting fly takes about 10 to 12 bloodmeals per day; blood loss can be significant because infested cattle may carry several hundred to thousands of flies. Traditionally, cattle producers have relied upon insecticides to control these flies. However, fly populations have developed resistance to most insecticides approved for use on cattle.

Organic dairy farmers have fewer options to protect their cattle from these pests. When the CEFS Dairy Unit began to study the feasibility of producing organic milk, it became imperative to develop an alternative fly management system. To address the horn fly problem, NCSU Entomologist Steve Denning designed a unique vacuum-powered walk-through fly-trap to remove flies from cattle as they pass through the trap (Figure 1).

Mean horn fly densities were above 700 per cow when the study began on May 29, 2007. Within one week of operation the device removed 410,000 horn flies from the cattle passing through, and during the second week an additional 457,000 horn flies were trapped (Figure 2). 

Mean horn fly densities were reduced from 775 to 263 per cow the first week, and by the third week fly densities were reduced to 150 flies per cow. The number of flies trapped by the third week had dropped to 216,000 and there was a 70% reduction in horn flies compared to a control group. By Sept. 26, 2007 over 2.4 million flies had been removed from 180 cows using the trap.

This innovative solution is now part of routine cattle management at the CEFS Dairy Unit and has allowed the herd to be insecticide-free for 5 years.

To learn more about the Pasture-Based Dairy Unit, visit the CEFS website.

From the August 2012 E-Newsletter