URBANA, Ill.-(UI Extension)--Late-January and early-February seem "a world" away from fly problems, but for cattlemen, fly problems are only three short months away. Face flies, accidentally introduced to the United States only about forty to fifty years ago, are one of those pests that will be around in less than ninety days.
Primarily a pasture pest, face flies tend to avoid livestock in confined areas except in cool weather. Often they will leave an animal as it enters a building, only to sit in wait on fences or vegetation for the next one that exits. They first emerge in the pasture during April after spending the winter months in protected areas, such as woodland trees or cracks and crevices within buildings. Following emergence they mate and lay eggs in the "cow patties" dotting the pasture.
The eggs take a while to hatch during those cooler days of April, but as the season progresses, those eggs may hatch within the span of a day. The emerging larvae feed and mature within the dung for more than a week after which they crawl into the ground to pupate. The entire lifecycle, from egg to adult, may take two to three weeks depending upon the temperature.
Upon first glance, the emerging adults resemble houseflies, and while the face fly is slightly larger, the two species are very difficult to distinguish between. Face flies are most commonly found around the eyes or nostrils where they consume the mucus released by the eyes and nostrils. Sometimes they may be found in other areas, such as around the mouth, where saliva is more prevalent. While houseflies may occasionally develop this behavior (in the driest of circumstances), face flies always frequent these areas regardless of environmental conditions. Only the female annoys the animal in this way. The male feeds on nectar.
During August, face fly populations swell, and during the daytime, face flies are most prevalent between the hours of 10 a.m. and 4 p.m.. As temperatures begin to drop below 50 degrees, the insect becomes less of a problem.
As far as rate of gain numbers are concerned, face flies are usually a "non-event" and hardly ever cause problems. However, their feeding is known to transmit the organism responsible for pink eye from infected animal to infected animal. This happens as livestock, plagued by this pest, bunch together in an effort to avoid the fly problem.
Few management options actually exist for the producer. While chemical treatments do exist, neighboring flies from untreated areas will often reinfest a pasture. Ear tags, prone to the development of insecticide resistance, can be used with limited success along with feed treatments, but all too often these pests are a common and difficult nuisance to manage.
