Face Fly Numbers Will Continue To Climb

LEXINGTON, KY.
   Face flies overwinter as adults in a variety of protected places: hollow tree trunks, barns, and attics to name just a few. That makes a fair number of them susceptible to being killed by normal winter temperatures. Survival is greater over a mild winter, resulting in higher populations to start the summer. Undoubtedly, we started the year with a lot more face flies than normal and are seeing the consequences.
   After leaving their winter shelter, female face flies soon begin to lay eggs in fresh cow manure. Development from egg to adult takes 2 to 3 weeks with the first generation of summer flies emerging in early June; this causes a noticeable increase in fly numbers on cattle. Face fly numbers continue to climb until August when a natural decline begins.
   Face flies are a real control challenge for three reasons: 1) they almost exclusively visit the face, which is difficult to keep treated; 2) they spend a very short time on cattle so there is little exposure to insecticides; 3) they are strong fliers that may move in from herds that are several miles away. This puts extra pressure on fly control programs.
   Many brands of insecticide cattle ear tags can suppress face fly numbers below what is present on untreated cattle in the area. Effectiveness can be very high during the first few weeks then control tends to drop to about 50 percent. This can be satisfactory unless fly populations are very high, which seems to be the case this year.
   Supplemental face fly control may be needed. Forced use dust bags or oilers with fly strips hanging down to treat the face should help to reduce face fly numbers. These probably will need to be in place and recharged until early August. Δ
   DR. LEE TOWNSEND: Extension Professor, Entomology, University of Kentucky