In July of 2024, after significant flooding in northwest Iowa, one packer reported 18% to 75% of market hog loads having carcass damage due to biting pests, says Colin Johnson, Iowa State University Extension and Outreach swine specialist. With the abundant rainfall in parts of the U.S. resulting in pools of stagnant water, he says it’s the perfect breeding environment for biting pests like flies and mosquitoes.
“Warm temperatures and wet/moist conditions, particularly stagnant water, propagate their lifecycle,” Johnson says. “Nearly every farmstead in the Midwest is a bit saturated at the moment.”
Time is of Essence
He reminds producers that insect populations can explode quickly. The adult pests often seen flying in the air or crawling represent a small portion (~15%) of the population.
That’s why lifecycle control and overlaying numerous site management steps such as drainage, mowing, ventilation, compost and manure management combined with insecticides and biological products such as sprays, feed additives, baits and traps is imperative.
“What fascinates me is that mosquitoes lay eggs on dry land and may lay dormant for months. Eggs reactivate and hatch quickly after significant rainfall or flooding,” he says. “Populations can grow and crash quickly. Some species flourish with floodwater conditions (Aedes vexans) and others in standing water and during late summer (Culex pipiens).”
Not Just Annoying
There is no question that biting pests are irritating to humans and animals alike. Johnson says this added stress on pigs can cause more than grouchy livestock.
“Decreased feed intake and increased energy expenditure resulting in decreased daily gains and feed conversion,” he says. “Milk production may also be reduced.”
Research shows the impact of biting pests also results in lost profit.
“Various diseases and injuries cause skin lesions that result in carcass trim loss,” Johnson points out. “Insect bites can cause discrete lesions such as papules on and below the skin that must be trimmed at harvest, potentially resulting in reports of $7 to $15 per head in lost revenue.”
Mosquitoes are well known for their ability to transmit disease, but Johnson points out the regular house fly can be a biosecurity hazard, too.
“Stable flies are the biting specie and while house flies are non-biting, they are quite a nuisance, cause messy spotting and are a pathogen spreader,” he says. “House flies are more of a biosecurity concern than a carcass concern. Black flies and biting midges are also wet habitat lovers.”
A study led by Allison Knox of the Walcott Veterinary Clinic in Walcott, Iowa, showed the ability of house flies and gnats to transmit rotavirus and sapovirus in swine nurseries.
“Flies and gnats are ubiquitous and hardy in the environment,” Knox said in a previous PORK article. “Practitioners and producers should consider including non-biting insect control protocols into farm biosecurity measures, as they may contribute to the reduction of rotavirus and sapovirus infections and transmission in swine nurseries.”
Minimize Risk to Your Herd
In addition to standing water, other conditions around the farm make a big difference when it comes to fighting these pests, Johnson says. Pay attention to compost or manure storage management, feed spills, pit crusting and vegetative growth. Other organic sites in the area matter as well, such as nearby feedlots, poultry litter or commercial and municipal sources of compost or waste processing.
“Consider implementing an Integrated Pest Management plan as a year-long mitigation strategy and view it is a vital part of your biosecurity approaches as well,” he says.
He encourages producers to keep production sites mowed, use a weed-free barrier around the barn and provide good drainage.
“Anything that improves site hygiene and aesthetics is generally going to also reduce pest populations,” Johnson says. “Be proactive, overlay preventative strategies and rotate products if using insecticides.”
A free resource is available with more information from Iowa State’s Iowa Pork Industry Center. Click here to download IPIC 209A, Integrated Pest Management in Swine Production Facilities.
