Animals bunching in the summer months due to fly pressure goes beyond making cattle uncomfortable, it can lead to economic losses due to decreased gains, milk production, and weaning weights. Making control difficult, 3 fly species are the main culprits when it comes to pestering our animals.
Face Flies
Face flies look like house flies but are slightly larger and darker. They feed on animal secretions, nectar, and dung liquids. They’re most common near water and moist, shaded areas. Numbers peak in late July and August. Face flies cluster around the eyes, mouth, and muzzle of cattle, causing extreme annoyance. Additionally, female fly feeding damages eye tissues, increases susceptibility to the eye pathogens that cause pink eye and spreading the infection around. Controlling face flies is essential in reducing most pinkeye problems.
Daily insecticide applications through dust bags, oilers, sprays, or insecticide-impregnated ear tags can control face flies, but both cows and calves must be treated. It is also important to rotate modes of action to prevent resistance.
Horn Flies
Next up are horn flies. These small flies take over 30 blood meals a day, often found on the backs, sides, and poll area of cattle. Horn fly feeding causes irritation, blood loss, decreased grazing efficiency, reduced weight gain, and lower milk production. Research from Nebraska shows that controlling horn flies can increase calf weaning weights by 10-20 pounds, and yearlings gains by 18% with treatment.
The economic injury level for horn fly treatment is 200 flies per animal. Like face flies, effective control methods include dust bags, oilers, sprays, and ear tags. Because horn fly eggs are laid in manure pats, oral larvicides can be effective control options by preventing larvae from developing into adults, though migration from neighboring untreated herds can impact effectiveness. Be mindful that other manure-utilizing insects, like dung beetles, can be affected as well.
Stable Flies
Stable flies are another serious pest, especially in feedlots and dairies. They primarily bite the front legs of cattle, causing painful reactions and weight gain losses. These flies breed in spoiled organic matter mixed with manure, often around feed bunks, hay stacks and winter feeding sites.
Studies from UNL have shown a 0.44 lb. per head decrease in average daily gain for untreated animals. Weekly sprays are currently the most effective control for stable flies on cattle. On warm days, targeting resting sites can also be beneficial. Cleaning waste feed and using larvicides at winter feeding sites can help reduce their numbers. Additionally, UNL is evaluating stable fly traps, with promising options available on the market.
Managing fly pests can be challenging, but it's crucial to figure out whether face flies, horn flies, or stable flies are your main problem to apply the right control methods. Your cattle will thank you for it, and so will your bottom line.
-Ben Beckman is a beef systems Extension Educator serving the counties of Antelope, Cedar, Knox, Madison and Pierce. He is based out of the Cedar County Extension office in Hartington. You can reach him by phone: (402) 254-6821 or email: ben.beckman@unl.edu