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Stark-Billings County |
Extension Spotlites
July 3, 2008
Cattle Fly Control
As the grazing season progresses, fly control will begin. The easiest answer is to do nothing and hope that horn fly populations remain less than 100 per side of the animal. Several research studies, including those conducted in North Dakota, indicate that economic losses in cow and calf productivity occur when the biting horn fly population is greater than 200 flies per animal.
Several methods can be used alone in combination to control fly populations. However, since flies can migrate, attempts to control flies on your herd but not on the adjoining pasture will provide only partial effectiveness.
Ear tags can be installed that contain insecticides. These insecticides can be very helpful in reducing horn fly numbers as long as resistance is not developed. Rotating use of insecticide type from pyrethroid to organophosphate will help reduce insecticide resistant flies.
Since peak fly populations occur during July and August, applying insecticides just before and during will provide the most control. Since insecticide ear tags lose their effectiveness over time, the best time to install or reinstall tags would be late June- just prior to rapid fly population increases.
Horn flies have a life cycle that starts when the female fly lays eggs on cattle manure. The larvae hatch in one day and then develop on the pupae for 2-4 weeks before emerging into adults. Several generations can be completed during the summer.
Feed additives provide another form of insect control via the manure. Rabon is a larvicide that affects the larva in the manure. IGR- insect growth regulator is an insect hormone that controls larva growth. The beef cow eating a supplement or mineral mix containing Rabon or IGR will provide good control of future fly populations. These products need to be fed early and through out the grazing season for good control. Adequate intake as specified by the manufacturer is required for success.
Dusts, oilers, and sprays work very well as long as cattle are treated regularly throughout the season to maintain control. The high labor effort required to provide continual applications and the need to treat all animals lead herd managers to consider alternatives. ‘Pour-on’ parasite products can also control fly populations. In general, the longer the product residual, the longer the horn fly control. Multiple applications may be needed for season long control. An alternative may be a one application of long residual ivermectin in late June.
For more information contact:
Kurt Froelich,
Extension Agent
NDSU Extension Service
Stark-Billings County
1340 W. Villard St.
Dickinson ND 58601-4646
(701) 456-7665