Fighting flies with wasps
Stableflies and houseflies are major pests for feedlot and dairy cattle.
Work being done by Agriculture Canada’s research station in Lethbridge, Alta. might lead the way to better control with the help of natural predators.
The painful bites of stableflies stress cattle, reducing weight gain in feeder animals and lowering milk production in dairy cattle.
Houseflies do not bite cattle, but spread disease, reduce the aesthetics of livestock facilities and irritate employees and neighbors.
Parasitic wasps are natural enemies of these flies and might be useful as part of an integrated pest management program.
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Female wasps lay eggs in fly pupae. Eggs hatch and the wasp larvae eat the developing fly.
Wasps feed only on a select group of flies and are not harmful to people, plants or animals.
Agriculture Canada, Alberta Agriculture and feedlot operators joined forces last summer to survey parasites of stableflies and house- flies in southern Alberta.
Housefly pupae were provided to several feedlots. They stayed for one week to give time for native parasites to lay eggs in them. They were returned to Lethbridge and held for parasite emergence.
The process was repeated every two weeks from May to October in each of the 12 feedlots.
Parasites emerging from the pupae were sent to Agriculture Canada’s Ottawa research centre for identification.
At least four species of parasitic wasps have been collected to date. Of these, Muscidifurax raptor, M. zarapto and Nasonia vitripennis are widely distributed in North America. Trichomalopsis sarcophagae has been reported previously only in dairies near Lethbridge and eastern Nebraska. A colony of this variety is now being maintained at the Lethbridge centre for further study.
Small, non-pest flies and beetle larvae also have been recovered that might be parasites of houseflies.
Overall levels of parasitism were less than one percent, indicating efforts to increase natural levels of parasitism might be useful in reducing populations of fly pests.
A similar survey was also done by Alberta Agriculture in feedlots north of Calgary and together the surveys will help identify native parasite species for further study as biological control agents.
– Agriculture Canada
