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home : news : print edition (click here) July 25, 2017

5/15/2017 3:40:00 PM
Swatting down on flies
Assess environment for best fly control option
Nolan Lenzen uses two fans on either side of the parlor’s entry way to remove flies from the cattle and trap them behind luevers installed on the box fan. Lenzen milks 25 cows near Eagle Bend, Minn. PHOTO BY JENNIFER COYNE
Nolan Lenzen uses two fans on either side of the parlor’s entry way to remove flies from the cattle and trap them behind luevers installed on the box fan. Lenzen milks 25 cows near Eagle Bend, Minn.
When the fan luevers are shut, the flies are caught in a screen entrapment behind Lenzen’s parlor. Last year, Lenzen collected a full 5-gallon bucket worth of flies.PHOTO BY JENNIFER COYNE
When the fan luevers are shut, the flies are caught in a screen entrapment behind Lenzen’s parlor. Last year, Lenzen collected a full 5-gallon bucket worth of flies.
EAGLE BEND, Minn. - Warmer days and wetter grounds are sure signs of spring, but they are also tell-tale indicators of a season much less desired by dairy producers.
"Flies have always been a bugger on my farm, and I'm always looking for ways to control them," said Nolan Lenzen, who milks 25 cows on his organic dairy near Eagle Bend, Minn.
In the Midwest, flies start to make a presence in April and May, with populations peaking in July and stay high through September. However, if the dairy farm is assessed early and proper controls are implemented, the effects of flies on cattle and humans are minimal.
With female flies laying 150 to 200 eggs at one time, and with a fly's life cycle only lasting 10 days, it becomes nearly impossible to eliminate flies in a farming environment, said Heather Schlesser.
Schlesser is an extension educator with University of Wisconsin-Extension in Marathon County. In addition to working with producers in Wisconsin, Schlesser has also helped dairy producers in Nicaragua grasp the consequences of too many flies on the farm.
"My goal is to make all cattle producers more aware of the situation," Schlesser said. "Flies will always be there. We have to learn how to manage them to keep them away."
Although there are many fly species, the most common found on dairies are house and stable flies, each posing different risks to the farm and surrounding areas.
"House flies are known for moving substances, so they're a vector of disease transfer," Schlesser said. "They are more of a nuisance because they don't bite or cause harm to animals."
Stable flies, on the other hand, have small biting mouthpieces and suck blood from their hosts.
"Every time they pierce the skin, they are hurting the cow," Schlesser said.
There are four methods to controlling the presence of flies on a farm - cultural, biological, chemical and physical.
Before choosing a method of control, Schlesser urges producers to evaluate the environment and determine how many flies are present. If more than 250 house flies are found in a trap, a control method should be implemented. The same is true if 15 animals are observed and more than 10 stable flies are present.
"If a fly population is high, producers can expect to see a 15 percent decrease in milk production," Schlesser said. "It's important to identify the type of fly and how many are present to know what control will work best to make an impact."
Despite maintaining a clean barn and housing environment for his cattle, Lenzen struggled for several years with flies. During peak fly season, he was applying more than two gallons of a natural substance on his cattle's feet and legs as they walked through the milking parlor.
"There were two months of summer when I didn't want to milk because the flies were so bad," Lenzen said.
In recent years, the use of traditional spray insecticides has decreased as the insects develop resistance to the active ingredients. With this, other forms of control, often natural-based, have become popular.
"The best cultural control is keeping the environment clean," Schlesser said. "Spread manure thinly so it dries, and keep grass cut because tall blades become a nice resting spot for the flies while they're waiting to lay the eggs."
Some producers might incorporate natural enemies, such as beetles, mites and wasps, in the environment to feed on the flies. If the environment is capable of hosting Purple Martins and Blue Jays, these birds will also decrease the fly population.
Other controls may include ear tags and neck collars that have a chemical component to deter flies from landing on the animals, as well as physical controls like insect zappers and tapes.
"Ear tags are becoming more popular; but if you're organic, check with your certifying agent before using any substance," Schlesser said. "Sometimes, bait is a better method of control that does not affect the biological agents."
After Lenzen evaluated his farm and tried several methods of control, he attended a summer field day to view a contraption that captured flies as the cows walked into the milking facility.
"On my way home, I started thinking of better ways to do that," Lenzen said. "By the time I got home, I knew what I wanted to do."
Last May, Lenzen mounted a squirrel cage fan in the entryway to the platform of his single-8 parlor. Across the platform, a large fan was installed into the wall of the facility with louvers placed on the backside of the fan; and behind the louvers was a screened entrapment.
Once the project was complete, fly season arrived at Lenzen's farm.
"The flies were just starting to bother the cows one evening, so I turned the fans on and watched it suck the flies right off the cows in droves," Lenzen said. "The rest is history."
Last summer, Lenzen collected a full 5-gallon bucket worth of flies from the entrapment and estimated that 70 percent of the flies on the farm were caught. By eliminating flies on the farm, Lenzen saw substantial improvements in his herd's health.
"I had the best milk production yet, lowered somatic cell count, and our reproduction was better than it has been the past five years," Lenzen said. "I wouldn't milk cows without this fan setup."
Now, Lenzen has plans to install another trap at the exiting end of the parlor this spring, and use both traps when the cows are in the parlor.
"With another fan set up, I'll collect well over 90 percent of the flies," Lenzen said.
While this physical control will not work for all dairy farm setups, Lenzen encourages fellow producers to find a form of control that will lessen flies' nuisance on the farm and surrounding areas.
"Flies are always going to be a problem," Lenzen said. "If you think you're fly control is adequate, there's always room for improvement."

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