Herd Health

HERD HEALTH New Ways to Treat Horn and Face Flies in Cattle

Producers know that Horn and Face Flies can irritate cattle and cause weight loss. Fortunately, they have a broad arsenal of products to combat them, with more fly treatments than ever before. This article will highlight the many options producers have to combat these production-limiting insects. Keep in mind timing is critical and we can save dollars by not overtreating a common mistake.

Horn flies are the ones producers see over the cattle’s backs in the summer. They spend most of their time biting through the hide (20-40 times daily) and drawing blood. This biting and irritation makes cattle nervous, resulting in less milk production. Milk production can be reduced so much that weaning weights may be reduced up to 14% on calves. The calves are doubly affected—they have less milk to drink, and the flies irritate and bite them as well.

Face flies feed on animal secretions such as eye discharge and are very bothersome to cattle, and this may result in up to one hour less grazing per day, leading to less weight gain. Face flies also play a significant role in spreading diseases such as pinkeye, which also decreases production and may result in the permanent eye scars we see, if the infection gets bad enough.

Both the Face fly and Horn fly life cycles involve eggs being laid in cattle manure. With the entire life cycle lasting two to three weeks, up to five lifecycles can occur in the summer. We should only treat when the numbers get high enough (see chart). We want numbers on average approaching 150200 before we initiate treatment or fire up our oilers.

With these flies, herd sires are the ones to closely watch— producers know that they can scrape them off the backs of bulls by the handful when infestations get bad. For a lot

Roy Lewis DVM

of producers, timing of infestations is highest in the peak of the summer when many bulls are breeding. For those that calve early, the breeding season gets ahead of the fly season, which is a great thing.

Producers should think about fly control whenever they are processing cattle in the summer or are transporting cattle to summer pasture. Fly control products can help make it easier to manage the pesky insects and can help producers achieve the economic and emotional returns that come from weight gain and healthy cattle.

There are several fly control options available and one should start off with one treatment, only when fly numbers get high enough. The ideal time may vary from time to time. Options available may even need to be changed from time to time.

Ivermectin products treat infections and infestations due to gastrointestinal roundworms, eyeworms, lungworms, grubs, sucking lice and mites in cattle, and although producers and veterinarians may not think of them for fly treatment, they also provide control of Horn flies and Face flies. Consider though, that in fly control season, internal parasites may be worthy of treatment but lice really don’t show up until fall, so most producers may save this for a fall treatment of their

A single small patch of flies = 25-50 A, B, C each being single patch = 75 flies

A patch covering 2 areas = 100-125 flies A & B, or B & C patch

A large patch covering all areas = 200-350 flies Covering A, B, & C