Control Stable Flies This Wet Spring

US - A wet spring in much of the state means livestock producers need to be diligent about controlling stable flies this summer, University of Nebraska-Lincoln entomologists say.

24 May 2007

3 minute read

North America

Stable flies are best controlled by sanitation and careful use of insecticides, said Jack Campbell, entomologist at UNL's West Central Research and Extension Center at North Platte.

"Stable fly attack on feedlot cattle can reduce weight gain and feed efficacy as much as 10 to 15 percent," Campbell said. "Maintaining dry conditions in the feedlot or dairy pen will greatly reduce fly breeding since flies need moisture mixed with organic matter to develop."

Feedlot and dairy facilities should be designed or modified to facilitate ease in cleaning, good drainage and to minimize waste accumulation, he said.

Major feedlot breeding areas include behind feeding aprons, under fences and gates and along and behind mounds, said David Boxler, UNL entomology research technician.

Bedding in sick pens and calf hutches, drainage areas and debris basins around pot holes (low areas), old hay stack butts, edges of silage and haylage drainage areas, and areas along and under feed bunks and around leaky waterers also are prime breeding areas, he said.

The Institute of Agriculture and Natural Resources specialists recommend livestock producers drag pens to reduce moisture and fill low areas.

"Some operators drag pens with a harrow, others make drags from worn out road maintainer blades," Boxler said.

Cattle and horses are the primary hosts for stable fly attacks, but the flies also will feed on dogs and people, Campbell said. Stable flies feed mainly on horse and cattle's front legs, dog ears and people's ankles.

"Cattle under attack will bunch, each animal trying to protect its front legs," he said. "If bunching occurs during hot, humid weather, animal heat stress will increase. Bunched animals can't dissipate excess heat."

UNL studies show a 0.2 kg/day weight loss from stable flies attacking grazing steers.

Stable flies don't breed in rangeland or pasture areas, but they can migrate to grazing cattle.

Stable flies breed in wet decaying organic matter, spilled wet feed and wet manure. In addition, they favor breeding in feedlot soil, dairy and winter cow herd feeding grounds and lawn clippings found around yards and golf courses. Improperly managed compost piles also serve as a stable fly breeding area.

Stable flies are dark colored, three-fourths of an inch long and have piercing bayonet-like mouthparts that extend from under their head.

They resemble house flies except for their mouthparts and checkerboard markings on the underside of the abdomen.

The life cycle of a stable fly consists of egg, larva (maggot), pupa and adult. It can be completed in about three weeks during warm weather and longer in cooler weather. The flies overwinter below the frost line in certain decaying organic matter areas such as manure piles. There is speculation that they also migrate from the south with storm fronts in the spring.

Specific insecticide recommendations can be found by consulting Nebraska Extension Circular EC1550, Nebraska Management Guide for Arthropod Pests of Livestock and Horses, available from local extension offices or online. More information also is available at UNL's entomology Web site. Use only insecticides registered for use on or around livestock, Campbell said.