Control Stable Flies This Wet Spring

They can reduce weight of feedlot cattle.

Published on: Jun 1, 2007

A wet spring in much of the state means livestock producers need to be diligent about controlling stable flies this summer.

Jack Campbell, University of Nebraska-Lincoln entomologist in North Platte, says stable flies are best controlled by sanitation and careful use of insecticides. "Stable fly attack on feedlot cattle can reduce weight gain and feed efficacy as much as 10 to 15%," Campbell says. "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.

Major feedlot breeding areas include behind feeding aprons, under fences and gates and along and behind mounds. David Boxler, UNL entomology research technician, says bedding in sick pens and calf hutches, drainage areas and debris basins around 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.

UNL entomologists recommend dragging 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 adds.

Cattle and horses are the primary hosts for stable fly attacks, but the flies also will feed on dogs and humans, Campbell says. 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 says. "If bunching occurs during hot, humid weather, animal heat stress will increase. Bunched animals can't dissipate excess heat."

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.

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 at www.ianrpubs.unl.edu/sendIt/ec1550.pdf.  

More information also is available at UNL's entomology Web site at entomology.unl.edu. Use only insecticides registered for use on or around livestock, Campbell says.