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Fly Control Begins Now

June 9, 2020

Jim Dickrell

It is never too early to plan and begin to implement seasonal fly control on your dairy and in your heifer raising operation, says Rick Hack, a veterinarian trained in entomology with Elanco Animal Health.

“Elimination of all breeding areas is really not feasible to prevent adults from repopulating,” he says. “But controlling larvae is a proactive preventative measure so adult flies do not lay eggs and repopulate. Managing both larvae and adults is a continuous process.”

Areas to clean-up regularly: Manure that is not removed frequently, decaying garbage and silage, commodity bays with spoiled feed, long grass around buildings and manure storage areas, and nearby wooded areas.

Another key is simply identifying the type of fly that is prevalent in your milking herd, calf hutches and heifer pens:

• House flies. While considered a nuisance, house flies are capable of carrying more than 100 diseases including pinkeye, mastitis, bacterial scours, typhoid, anthrax, vibriosis and several clostridial diseases. They can also transmit antibiotic resistant bacteria and increase bacteria counts in milk. Adult house flies can be found just about any where in buildings, but are common on interior surfaces and windows where they typically rest.

• Stable flies. These pests are typically found on the legs of animals, and they face upwards when feeding. Just 5 flies per leg can cause economic loss, with some studies showing a milk loss of more than 3 lb/cow/day. Feed efficiency also drops. “Cattle can exhibit avoidance behavior that reduces the time spent feeding and resting,” says Hack.

• Face flies. These buggers are typically found on the face and head of animals. Pinkeye transmission is their claim to fame, says Hack.

• Horn Flies. Horn flies are most typically found on the backs and bellies of cattle, and they are the number one pest of pastured cattle. When feeding, they pierce the skin of cattle with painful bites to ingest blood, and can feed 20 to 30 times per day. In heavy numbers, they can reduce milk production of grazed cows by 20%.

Controlling flies requires an integrated management plan that includes inspection, sanitation, treatment and monitoring.

Inspection means identifying which type of fly or flies is most prevalent on your operation. Sanitation requires on-going daily and weekly efforts to keep the facility as clean as possible to reduce breeding sights. Create a map of your facility that identifies problem areas, and then routinely ensure these areas are cleaned frequently, says Hack. Monitoring simply means incorporating routine inspections to check fly populations to determine if your sanitation and treatment program is working.

“Treatment requires applying the right product in the right way for the right fly,” he says. Your treatment program should include larvicides used in conjunction with adulticides that will act on multiple life cycle stages and provide more successful fly management results, says Hack. “Use larvicides continually and adulticides when needed,” he says.

If you only treat adult flies, you will be behind the curve and never catch up. That’s because adults represent just 20% of the fly’s life cycle. So if you just treat adults, larvae will simply just keep maturing.

Larvicides include spinosyns, growth regulators and organophosphates. Adulticides include pyrenthroids, neonicotinoids, spinosyns and organophosphates. “It’s important that you don’t use the same type of insecticide on larvae and adults at the same time to prevent the build-up of resistance,” Hack says.

You must also read and know the label of each product, and which class of animals—lactating or non-lactating—for which they can be used.


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