NEW PRAGUE, Minn. — Flies can multiply on farms rapidly if control measures are not implemented.
“A typical life cycle for a fly from egg to egg is seven to 10 days in the summer, so populations can increase very quickly,” said Rick Hack, RJH Consulting LLC business consultant.
“Controlling larvae is a proactive process so adults cannot lay eggs and managing adult flies is a continuous cycle throughout the fly season,” Hack said during a webinar organized by the Dairy Calf and Heifer Association.
“A good program consists of using the right product at the right time in the right way,” Hack said. “The key thing is to read the labels.”
Four flies — house, stable, face and horn — can be problems for livestock operations.
“The stable and horn flies are blood feeders and the house and face flies are premise and pasture pests,” Hack said.
Stable flies like high fiber substances for breeding areas such as straw, hay or bedding around calf hutches.
“They love decomposing hay, grass and the bottoms of big round bales in pastures where the hay meets the ground,” Hack said. “The moisture is perfect for stable fly heaven.”
Economic loss can occur when there are five or more flies per leg of an animal.
“Stable flies can engorge blood for two to five minutes, so you will see animals stomping and throwing their head back,” Hack said.
According to data from the University of Nebraska, the impact of stable flies on feeder cattle dropped feed efficiency 10% to 15% and gains were reduced by 0.2 to 0.5 pounds per day.
“When cattle are using their energy to get the flies off their legs, bunching in a corner or not eating, milk production can be reduced by almost 2.2 pounds per day,” Hack said. “Stable flies cost the livestock industry $2.2 billion per year.”
Horn flies are often found on the backs of cattle and in high temperatures the flies will be on cattle bellies.
“This is the No. 1 pest for pasture cattle costing more than $876 million per year,” Hack said. “Stocker gains can be reduced 15 to 50 pounds and milk production reduced by 20%.”
A horn fly is about half the size of a stable fly.
“Horn flies feed 20 to 30 times per day,” Hack said. “When the animal throws its head back, you will see a fog of flies.”
When house flies land, they vomit or drop feces which leave a speck. They are found on indoor and outdoor surfaces, including manure for the larvae and around windows, railings and manure areas that are difficult to clean for adults.
“House flies breed in organic material so keep water leaks under control,” Hack said. “Organisms are on the hairs of the flies which can transmit antibiotic-resistant bacteria.”
Face flies breed in manure pats.
“They land on the face of cattle and walk up to their eyes,” Hack said. “They also feed around the secretion of the eyes, so they are famous for transmitting pick eye and they are difficult to control.”
Hack recommends a proactive fly control program that targets both adult and larval populations.
“As we walk around our facilities, the elimination of all breeding areas is really not feasible,” he said. “We need to do our best to keep our facilities clean, but flies will find a place if breeding areas are there.”
While inspecting a facility, Hack encourages farmers to develop a diagram of where the flies and larvae are present and the fly species that are observed.
“Look at hutches, side of buildings, on curtains, corners of feed storage areas and the area under water buckets,” he said. “Cut your grass short because flies will rest in tall grass and then come back on your animals.”
Both larvicides and adulticides are available for controlling fly populations.
“Use larvicides in breeding areas early in the season to reduce adult populations and then continue throughout the season,” Hack said. “Use adulticides when needed to stay ahead of the curve.”
Hack stressed the importance of using different classes of insecticides.
“There are several kinds of larvicides, including a spray that is mixed with water to treat breeding areas or feed throughs,” Hack said. “Granular products are available for heavy moisture areas. You apply these and the product dissolves releasing the insecticide.”
Adulticide sprays are used to control adult populations of flies.
“Residual sprays are sprayed on walls and when an insect comes in contact, they are controlled,” Hack said. “Space sprays or foggers really only control adults that are hit with the particles.”
Options for on-animal fly control include pour-ons, ear tags, sprays, dips or dust bags.
“Rotate the chemical classes of ear tags and install them as close to horn fly season as possible,” Hack said.
“Monitor your fly control program with sticky tapes or speck cards,” he said. “And keep a record so you are able to see how the products are working.”