Extra Rainfall Means Extra Work for Pork Producers Now

Aug 11, 2025

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.

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