Natural predators for cattle flies
An average cow on pasture produces 13 cowpats per day. An estimated 4.16 million cattle on summer pasture in Alberta in July can produce 40 million cowpats per day.
These cowpats provide a habitat for various insect pests, their predators and parasites (natural enemies), and parasites of cattle themselves.
Two major cattle pests that breed in manure are horn flies and face flies. In severely infested herds, the cows may carry 5,000 horn flies and bulls up to 10,000.
Face flies cause irritation and disrupt grazing, but also carry pinkeye causing path-ogens and nematode parasites of cattle.
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With increased resistance of these flies to insecticides, the biological control of livestock pests is one of the options that entomologists are exploring.
In the summer of 1995, an inventory of biological resources to control horn flies and face flies was initiated in southern and northeastern Alberta.
Field sampling and incubation of cowpats in the laboratory is near completion. Preliminary data has revealed four groups of beneficial dung beetles and parasitic wasps that are potential biological control agents.
- Dung-roller beetles: Two species of these beetles were found in the Nanton and Medicine Hat districts in limited numbers. These beetles carve small dung balls and roll them long distances. They deposit the dung balls close to grass or other vegetation, or dig small shallow pits and deposit the ball. They lay their eggs in these dung balls. They help the environment by cleaning up the manure and carrying soil nutrients away from the cowpats. They recycle the manure.
- Dung-burying beetles: These beetles dig tunnels underneath the cowpats. The sausage shaped tunnels are filled with manure and the eggs are deposited for breeding. By their activity, an appreciable amount of dung is buried, soil loosened and manure-fertilized which will increase the water retention of the soil. These beetles also play an important role by quickly disposing of manure breeding grounds for flies and nematode parasites of cattle.
- Dung-feeding beetles: These are most abundant in the early and late summer. They consume dung by tunneling and cutting holes. In the process, they dry the manure, making it unsuitable for fly larva to breed in and also aid in decomposing the manure. These beetles do not attack plants or roots. They use the manure for breeding and for shelter.
- Predatory beetles: These are very small and they arrive at fresh cowpats within a half hour of being deposited. They search and hunt for fly eggs and larva. Numerous beetles were collected from the day-old samples.
This is the project’s first year. Predatory dung beetles look most promising as a biological control and will be researched further.
– Ruminations newsletter
