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PEST
DIAGNOSTIC CLINIC
Laboratory Services Division, University of Guelph 95 Stone Rd. West Guelph, Ontario N1H 8J7 Phone: (519) 767-6256 Fax: (519) 767-6240 E-mail: pdc@lsd.uoguelph.ca |
In April cluster flies lay their eggs singly in cracks in the soil. During the summer, the eggs hatch and the emerging larvae (maggots) penetrate earthworms and develop as a parasite in its host. There are several generations during the summer. The adults stop egg laying in late August and September, and seek hiding places in which to overwinter. Most of the flies spend the winter outside in and on fenceposts, under stones, and in other protected places. Cluster flies are usually a greater problem in rural and suburban areas due to the large grassy areas that favour high earthworm populations. Cluster flies are not related to livestock production. They do not develop in manure or manure pits. They are not interested in food, do not develop in garbage, and are not a sign of unsanitary conditions. Controls: To prevent the entry of the flies in the fall, screen attics and roof vents and fill all cracks, crevices and other points of entry with caulking or other crack filler. Tighten baseboards and quarter round. Flies found on the windows can be killed with a fly swatter and removed with a vacuum cleaner. Insecticides registered for indoor control of flies can be applied between inner and storm windows or directly on insects. Planting tall vegetation on the south and west sides of the house will reduce the attractiveness of these walls to flies seeking warmth and shelter in fall. A registered pesticide sprayed on the sunny walls of the house may help. Treatment of sod areas near houses to control earthworms is not effective since adult flies can travel long distances. FOLLOW LABEL DIRECTIONS TO ENSURE THE SAFE USE AND EFFICACY OF EACH PESTICIDE PRODUCT. H.W. Goble/W.A. Attwater/R.T. Wukasch PDCF-032 (Revised 99/04/05) |
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Overwintering
adults of the cluster fly, Pollenia rudis Fab. are an annual
problem in many houses. Cluster flies are slightly larger and darker
than house flies, and have a coating of short golden hair on their
thorax. These flies normally live outdoors where they occur on flowers
and fruits. In late summer and fall, when the weather turns cool,
cluster flies may congregate on sunny walls. They enter the home to
overwinter through any available access. In the home, the flies hide,
often in a cluster in attics and wall voids, in dark corners, cracks,
under clothing in closets, beneath curtains, behind pictures and furniture
etc. On warm, sunny days in the winter and spring, the flies often
emerge from their hiding place and swarm on windows causing great
annoyance by their buzzing and by their presence. Dead flies provide
a food source for larder beetle larvae and can contribute to the presence
of other nuisance insects in the house.