Spring Fly Control

By Trey Gafnea

Even though it’s only March it is not too early to plan our fly control strategy for the spring and summer. The first step in developing an integrated program to control flies is to understand which flies are pest of our animals. There are four major fly species that attack southeastern livestock. These can be divided into two groups based on where they tend to live and reproduce. They are the “Pasture” flies which include Face Flies and Horn Flies and the “Premise” Flies such as Stable Flies and House Flies.

The Premise Fly group is also known as the “filth fly.” As this name suggests stable and house fly’s both reproduce in decomposing organic matter, this includes; grass clippings, wet hay, spilled feed and manure. Even though they can be a major source of irritation to animals and humans, these insects tend to spend more time resting on building wall and ceilings. Sanitation plays a major role in premise fly control strategies. Insecticidal premise sprays can be applied to flat surfaces to supplement facility cleaning for premise fly control. Feed through insecticides do help control larval development in manure, but do not address other sources of organic matter, such as spilled feed and damp hay.

Face flies and horn flies each require a different strategy for effective control. They lay eggs in freshly deposited manure. Even though both species of flies have this point in common, there are significant differences between the two flies that need to be accounted for when developing a control program.

Face flies as their name suggests tend to congregate around the eyes, nose and mouth. The protein found in eye secretions and mucus is important to the female face fly for egg production. This feeding habit aids in the transmission of pink eye among animals. They have been implicated in the spread of infectious bovine rhinotracheitis (IBR). Face flies can also cause a loss in milk production and weight gain. Face Flies are active in Georgia from March until November. The treatment threshold is only four to five flies per animal.

Control of face flies can be difficult due to the amount of time that the pests spend off of the animals. Pyrethroid insecticides applied as ear tags, back rubbers and dust bags are the most effective options for control. The active ingredients in these products include Permethrin, Cyfluthrin, and z-Cypermethrin. Feed through fly larvicides can be an effective tool for managing face flies.

Horn flies are the most serious insect pest of pasture cattle. If left unmanaged these flies can cause a twenty percent reduction in milk production in lactating cattle and reduce weaning weights by eighteen pounds or more. Horn flies look similar to house and stable flies, but are much smaller. These flies tend to rest onthe back, shoulders, sides and belly of the animals. Adult horn flies spend most of their life on the animals. Females only leave their host long enough to lay eggs in freshly deposited manure. Horn flies need to be controlled when they reach 100 flies per side or a total of 200 for an adult animal. Insecticidal ear tags, pour-on, sprays, dusts and feed additives all can be used for effective control. Many of the macrocyclic lactone dewormers are labeled to provide several weeks of horn fly control. Feed through insect growth regulators such as, Altosid® and Clarifly® can be an effective means of control as well.

Due to their reproductive cycle of only 10 to 20 days and our long fly season in Georgia. March through October insecticide resistance can be an issue.

Listed below are several strategies to minimize resistance:

Be sure to rotate product class not just brand names or type of product to minimize the resistance issues.

Typically organophosphate products would be used for two years and pyrethroids for one year. Common active ingredient of labeled organophosphate insecticides include; coumaphos, diazinon, pirimiphos-methyl and tetrachlorvinphos.

Do not insert ear tags until horn fly populations reach 200 flies per animal.

Many of the macrocyclic lactone dewormers are labeled to provide several weeks of horn fly control as well.

The most effective horn fly control strategy involves combining a several different control methods throughout the season.

Source:uga.edu