Shoo Fly! Iowa Beef Center Offers Tips for Fly
AMES, Iowa -- Bugs. One of the few drawbacks of summer. Whether
they crawl, fly, skitter or tunnel, insects are probably the most hated animals
on Earth. Even though most are only a mild annoyance, their sheer numbers,
dogged tenacity and ability to survive and breed in the most inhospitable
conditions have marked them as a public enemy.
Livestock operations, open lot and pasture alike, are about as close to heaven
as insects, especially flies, can get. Room to land, plenty of food and ample
breeding areas attract them from far and wide.
Flies can be problematic for Iowa's beef producers. Not only are they pesky, but
biting flies adversely affect animal performance and spread disease. Ken
Holscher, associate professor in the Entomology Department at Iowa State
University and cooperator with the Iowa Beef Center, said producers have several
options available for fly control.
"Fly control measures depend on two criteria: Whether the producer has
pasture or feedlot animals and what types of facilities and equipment are
available," he said. "All fly control options have limitations, so
producers need to evaluate their specific needs and choose wisely."
Pasture Control - Chemical
Horn flies and face flies are the two main species that affect pastured cattle.
Although the most effective means of controlling them are primarily chemical,
there is a variety of application methods. Equipment and facilities will dictate
which measures are best.
Sprays. "Fly sprays are effective and fairly inexpensive," Holscher
said. "However, the effectiveness wears off after about 30 days, so the
cows must be treated once a month throughout the fly season. Then the question
becomes can and do producers want to continue treatments?" Holscher added
that treating cattle during the hottest parts of the summer may cause stress.
Pour-Ons, Spot-Ons and Squirt-Ons. Pour-ons are ladled across a cow's back,
spot-ons are applied to one spot on the cow's back and squirt-ons are applied to
the backs of cattle using a squirt gun mechanism. All three are equally
effective, however, they still must be applied once per month.
Forced-Use. Forced-use methods include back rubbers and dust bags and are
relatively inexpensive and effective. "Using self treatment takes a little
more preplanning by the producer," Holscher pointed out. "Cattle have
to use these daily for them to work, so placing them directly in front of food
or water is the best bet."
Feed Additives. Feed additives control fly larvae developing in cattle manure.
"This approach takes a lot more management than the others," Holscher
said. "The cattle must ingest the right amount daily - not too much and not
too little. Obviously, cattle don't know a whole lot about their rations, so
producers need to be proactive when using this method."
speculation about resistance to ear tags, Holscher said they are still a
viable option for many producers. "For ear tags to work, producers
absolutely cannot use pyrethroid tags for more than one year. They should
alternate with organophosphate tags every other year," he said.
Pasture Control - Nonchemical
Mainly small producers will benefit from non-chemical solutions.
Bruce Fly Trap. The Bruce Fly Trap became popular in the 1920s and 1930s and is
experiencing a rebirth of sorts. Named its inventor, the fly trap is usually
built from wood or polyvinyl chloride pipe and fine screens. When the animal
walks through the framework, the screens scrape the horn flies off. It has no
effect on face flies, and cattle must be forced to use the fly trap every day.
Mechanical Controls. "Flies lay their eggs in fresh, undisturbed manure.
The manure must remain intact for the larvae to hatch, ," Holscher
explained. "Harrowing pastures regularly would break up the manure and kill
the eggs and larvae."
Stable and house flies are the main pests found in beef feedlots. House flies
are usually only a nuisance, but stable flies feed on blood and attack the
animals' legs and ankles with painful bites.
"The best method of controlling flies in feedlots is sanitation and manure
management," Holscher said. "Flies need manure and other materials for
laying their eggs. By trampling and scraping manure, eliminating standing water
and cleaning up spilled feed and silage, much of the fly problem can be
There are several products available to supplement sanitation practices.
Residual wall sprays last three to four weeks and are applied to areas where
flies rest. Knock-down sprays supply a quick but temporary removal of flies from
lots - they must be used daily. Feed additives can be an option, however the
active ingredients are deposited in manure, thus, they won't control flies
developing in other breeding materials.
"Some producers have tried parasitic wasps in their feedlots,"
Holscher said. "These wasps attack and destroy flies. They've been useful
in poultry confinement buildings, however, their use in feedlots is somewhat
limited. Studies are underway to determine why they don't work as well in
feedlots. Using this method requires a lot of management, because a person needs
to know where, when, how many and how often to release the wasps. It's probably
not the most feasible choice for Iowa feedlots."
None of the techniques listed have changed much over the past 20 years.
"There's really nothing new on the horizon as far as fly control,"
Holscher commented. "But the current technology is effective; we have to
make good use of what we already have."
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