Fly control is one of the top issues facing dairy farmers. Summer brings warmer weather, longer days, pasture growth and grazing – things that we all look forward to during the long, cold and dark time of winter. The explosion of life in spring also brings with it the perennial and unwelcome problem of flies. Flies cause both irritation and serious economic losses to dairy farmers by spreading disease, feeding on animals (causing blood loss) and greatly decreasing productivity in grazing cattle by triggering them to crowd together and stop feeding. Pinkeye, mastitis and other diseases such as bovine leukosis are spread among cattle by the actions of flies feeding on them.