Dung beetle death on flies
Flies are a problem for cattle, but the answer to controlling them could lie with another insect.
South Dakota State University graduate student Jacob Pecenka of Mitchell, South Dakota, is studying the role of the dung beetle in breaking down manure and controlling flies. The dung beetle can disrupt the life cycle of the fly when it breaks up the manure pat where flies lay their eggs. The beetle rolls away chunks of manure to bury. The manure dries, and with it, fly eggs dry and die.
“They’re doing this enormous service for free,” Pecenka said.
Pecenka is working at Blue Dasher Farms, a research farm started by former U.S. Department of Agriculture entomologist Jonathan Lundgren. The student is looking into different ways of managing cattle and how the changes affect insects that live in cattle droppings.
“That dung pat is a really neat resource,” Pecenka said.
But without help breaking them down, dung pats can become a breeding ground not only for flies, but for parasites that attack cattle.
“We’re creating our own parasite problems,” Lundgren said.
Pecenka has been doing his studies on farms near Hayti, Gary, Milbank and Flandreau, South Dakota, plus an organic farm near Sioux Falls, Iowa. He said he’s hoping to learn the best sort of grazing system to help beneficial insects, whether it’s season-long or rotational grazing.
One of his efforts looked into how quickly dung beetles break down manure pats. He placed dung on a grid and covered some pats with small screens to keep bugs out but allow other elements in. Other pats were left in the open.
The open pats broke down quickly with the help of insects – sometimes in a matter of days. The faster they break down, the less chance flies have to reproduce.
One problem though, according to Pecenka, is that treatments producers use to remove flies also cause the beneficial beetle to disappear. Many producers treat their cattle with a medicine to control parasites called Ivermectin. It can be used for intestinal worms and also to kill fly larvae in the manure.
Traces of the medicine are in the manure pat; Pecenka is finding it affects the number of insects living there.
“It’s good to keep the flies from laying their eggs in the pat, but you lose the other bugs, too,” Pecenka said.
He said it’s necessary to treat for fly control sometimes. Cattle won’t be comfortable if they’re always battling flies. It might be best, though, to administer more targeted treatments when needed. Pecenka said treating cattle in the fall is a better option than treating in the spring before sending the herd to pasture. In that case, relying on natural methods of controlling flies might be better than chemicals, he said.
“I think we often forget just how important insects are in rangeland and biodiversity,” Lundgren said.