Cow pies from cattle treated with parasite control products make unattractive homes for dung-breeding insects like hornflies.
It has already been established that residues of some types of pour-on endectocides are excreted in the dung of treated animals. These residues can reduce the numbers of dung-breeding insects.
Now, Kevin Floate and Doug Colwell from Agriculture Canada’s research centre in Lethbridge are comparing the success of different products using recommended doses in a pour-on formulation.
They have found that doramectin works best in reducing the numbers of flies breeding in manure. Ivermectin and eprinomectin had similar results, but less than that of doramectin. Moxidectin had the least effect.
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Bad for good guys?
Endectocide may also reduce the number of non-pest insects in dung, including parasites and predators of pest flies, as well as beetles that accelerate the breakup of the dung pat.
Researchers found that hornflies are most affected by the treatments. Fly numbers were reduced in dung from cattle that were treated up to eight weeks previously with ivermectin.
Hornflies were reduced in dung of cattle treated at least four weeks previously with doramectin and eprinomectin. Moxidectin reduced hornfly in dung of cattle treated one week previously.
Nip in bud
Adult insects swarming around the cow pats are not greatly affected by the chemicals residues. However, larvae and eggs are killed, which is a more desirable way to control insect populations.
Floate said timing may be an important tool.
The product should be applied early in the season before cattle go on pasture, where they may pick up more pests.
Ranchers should evaluate the formulations for themselves to measure how much fly control they
obtain.
“If used as directed, all these compounds are quite good,” he said.
“Follow the label instructions. Sometimes people go overboard.”
This summer, Floate and his team plan to monitor how the chemicals affect beneficial insects that break down cow patties.
Researchers are not sure how long the compounds last in the soil. European research suggests that they bind to the manure itself and do not lose their toxicity. However, they believe the compounds are eventually broken down by soil microorganisms.
