Better Manure Breakdown With Beetles

Dung beetles are more likely to be the butt of jokes than part of a serious pasture plan. But these aptly named insects improve manure breakdown and nutrient availability in soil while reducing fly populations and allowing for more thorough foraging.

“Most farmers don’t realize dung beetles are present in their pastures,” says biologist Nadine Kriska, who lectures at the University of Wisconsin-Whitewater. “But if you look at a fresh manure patty where it meets the soil, you may see some holes or even pockets on the surface. And if you disturb the patty, you will likely see beetles scurrying.”

At least 185 beetle species are found in Wisconsin, she says, and about one-third of them are types of dung beetles. “In Wisconsin we’ve found 26 species associated with cow dung, alone.”

Of more than 90 dung beetle species in the U.S., the most common are tunnelers and dwellers. Tunnelers make and bury dung or brood balls under patties or slightly underground, where they lay eggs. After eggs hatch, larvae live in and eat the balls’ inner contents until young adults about three weeks later. Dwellers live and reproduce within manure patties.

Most beetle species reproduce in about six weeks, says Kriska. “There can be several species living in one pasture, and no one species is better than another. The more the better.”

Beetles will travel to new pastures with fresh dung. With a keen sense of smell, most can find dung up to a mile away.

Most dung beetle research was done in the 1980s in the warmer climates of Texas and Oklahoma, the biologist says.

“But our research shows that there are plenty of species here in Northern states. We just need to recognize them and try to foster their existence in pastures.”

Dung beetles offer benefits, for livestock and pasture health, in any part of the country. They include:

• Fly control – Beetles can remove dung before horn and face flies lay eggs in it. Some also prey on maggots, reducing fly populations.
• Parasite control – Some beetles carry mites that don’t harm them but do eat parasite and fly eggs in dung.
• More complete foraging – Cattle won’t forage near patties, so when beetles break dung down, more pasture is ready to be grazed.
• Better nutrient uptake – By breaking down patties, beetles make nutrients such as carbon and nitrogen more available to pasture plants.
• Water absorption – Tunneling beetles improve the soil’s structure by increasing its capacity to absorb and hold water.

• One of the biggest threats to dung beetles in pastures? The insecticides used to control internal parasites in cattle. Ivermectin products, especially one to two weeks after application, can significantly reduce beetle populations, Kriska says.

  To avoid this, she recommends treating cattle for parasites in cooler months, when beetles tend to be more dormant. In the Upper Midwest, beetles usually become active in March or April and go dormant in October or November.

  “It takes about two weeks for beetles to break down patties in Northern states such as Wisconsin. In the southern U.S., it may take only a few days to a week.” While farmers can’t base their pasture rotations on that, it’s one more bit of information to add to the management mix, Kriska concludes.

  It’s hard to quantify the specific benefits of having dung beetles in the pastures of Doug Delling’s small organic beef operation near Ontario, WI. “I see how they break down the manure. After about two weeks, all that’s left is the outer shell of the patty,” he says.

  How much that improves his soils, he can’t put a number to. “But I have healthy-looking pastures. To me, having dung beetles present is another indicator that I have good soil life there. Nutrients are going back into the soil and runoff is not a problem.”

  To identify dung beetles, go here.