By Blake Jackson
During summer, anyone familiar with barns or cattle pastures knows the nuisance and health risks flies pose. Face flies can spread diseases like pink eye, while horn flies - biting insects that feed on cows up to 20 times a day - can negatively impact cattle health and growth if present in large numbers.
However, common insecticides used to combat these pests may be doing more harm than good by killing beneficial insects like dung beetles, which naturally help control fly populations.
Cornell’s Integrated Pest Management (IPM) program has partnered with farms across New York to examine how feed-through insecticides - added to cattle feed - affect dung beetle communities.
These researchers are also promoting alternative pest control methods, including walk-through fly traps, protective shelter, and using poultry to eat fly larvae.
“These flies can cause major problems for herds. If you’re raising steers, you want them to gain weight quickly, and the annoyance, injury and disease that flies can cause in large numbers can affect the animals,” said Ken Wise, livestock coordinator for Cornell Integrated Pest Management (IPM).
“However, the broad-spectrum use of any insecticide is not an integrated approach to controlling flies. I know it’s a pain to do, but if you can estimate the number of flies on your cows and treat the animals only when they need it, you’re going to have a lot less insecticide in the environment.”
Both flies and dung beetles lay eggs in manure, where their larvae develop. Dung beetles, along with predators like rove beetles and water scavenger beetles, reduce fly populations and improve soil health by breaking down waste and cycling nutrients.
Current research by Wise, Bryony Sands from the University of Vermont, and Cornell’s Hannah Tolz compares a broad-spectrum insecticide and an insect growth regulator (IGR) for their impact on these populations.
Initial results show a significant decline in dung beetle numbers and diversity on farms using feed-through insecticides. Interestingly, horn fly counts rarely reached levels that warranted treatment.
Farmer Kate Marsiglio, of Stony Creek Farmstead, avoids insecticides by rotating her livestock and letting chickens forage for larvae. “The chickens come through and scratch out the cow pies, spread them all out, and then eat the fly larvae. I also love watching wild birds follow our cows: You see birds on their backs, eating insects and creating this great beneficial relationship.”
Cornell IPM urges farmers to apply insecticides only when fly levels surpass thresholds and to use targeted methods such as face rubbers, dusters, and mechanical fly traps instead of widespread feed-through treatments.
Photo Credit: gettyimages-diane-kuhl
Categories: New York, Livestock, Beef Cattle, Dairy Cattle