Control Flies and Minimize Resistance to Insecticides

Nuisance flies can reduce performance and lower profitability. Producers should implement fly control programs that protect livestock and reduce the chances of insecticide resistance.
By: Frank Wardynski, Michigan State University Extension

While flies are seldom cause mortality problems in beef cattle, they frequently cause stress and discomfort to cattle through the summer months. Fly control is an important economic management decision that needs to be made with concern of potential insecticide resistance problems. Fly populations across the country have developed various levels of resistance to insecticides.

Producers should manage the use of pesticides to minimize resistance before available pesticides become totally ineffective. Fly tags are frequently an effective method of using insecticides to provide season long protection. To minimize resistance producers should apply tags when they are needed. Applying tags will reduce their effectiveness later in the season. Tags should be applied as flies become a problem and removed after flies have subsided or the usefulness of the tags has been exhausted.

Insecticide classes should rotate from one year to the next. Pyrethroids and organophosphates are two classes available to be alternated. Alternating chemical classes isn’t just for the ear tags. Insecticides used as ear tags, sprays, and powders should be rotated. Sprays and powders can be used to supplement or instead of ear tags. Also macrocyclic lactones in the pour on form can be used to supplement fly control with minimal resistance problems. Macrocyclic lactones are a class of anthelmintic commonly used to deworm livestock.