It Takes a Village (of Insects) to Raze a Manure Pile

Jacob Pacenka and Jonathon Lundgren documented the dung insect community in South Dakota and determined dung degradation rates in the presence and absence of insects.

Dung beetles are the “charismatic megafauna” of the dung-degradation world. They’re what we think of first. But, according to an article in PeerJ, they couldn’t do their job nearly as well without a whole host of arthropods joining in. In fact, researchers found that dung beetles make up only 1.5-3% of the population of insects that process poop in pasture. In addition, the more diverse and abundant the population of arthropods, the more dung beetles you’re likely to have and the more quickly dung will degrade into the nutrients that improve soil and help your pasture plants grow.

Speed is of the Essence

Turning a dung pat into nutrients in the soil as quickly as possible is important. Left on the surface, it can smother plant growth, and can reduce the area where animals graze. In addition, 22% to as much as 80% of the dung’s nitrogen can volatilize into the air in 60 days, and other nutrients can be lost to leaching and runoff. The result is reduced nutrients important for plant growth, and lower quality forage for livestock.

Enter the Arthropods

Fortunately, the arthropods start to work as soon as a dung pat is deposited. In fact, most dung degradation occurs within a week of the dung hitting the ground, with the insects doing most of their work in the first two days.

Dung beetles arrive quickly to feed on the liquid portion of the dung. As the dung pat dries, they move on to others, leaving their eggs behind. Those eggs turn into larvae that feed on the fibrous portions of the pat. Dung beetle tunnels also become avenues for spiders and other predators to move through the pat, furthering degradation as they search for eggs, larvae, flies and more.

What makes up a dung pat community? Researchers collected almost 87,000 specimens, representing 13 orders of arthropods including insects, spiders, millipedes, and more. They also found that dung beetle abundance and diversity increased with arthropod species richness and population.

They also compared rate of degradation between dung inhabited by arthropods, and dung without them. They found that insects speed the rate of degradation by about 30%.

Arthropod Communities Change With Time, Temperature, and Grass Species

Researchers compared dung pat populations in the early season and later in the grazing season and found that in the early season, peak population occurred in 7-day-old pats. Later in the season peak abundance was at 2 to 4 days. Temperature may be one reason for this difference. Dung pats dry more quickly at higher temperatures, so the arthropods must move in earlier. In addition, different species have different life cycles, and appear during different times in the grazing season. Finally, as cool season grasses are replaced by warm season grasses, the composition of the dung pat itself may change, making them less attractive to some arthropods.

What Can You Do With This?

If you’re thinking of manure as one of the resources helping you build healthy soil, you might want to keep in mind the creatures the needs of the creatures moving nutrients from the manure to the soil. Insecticides, fly treatments and worming medications can all reduce their populations.

Here’s an article you might find helpful when you’re considering alternatives to things that endanger your dung-degrading insects. Though it targets pinkeye, it also covers management tools that reduce parasite and fly problems without chemicals:

Fly Management to Reduce Pinkeye Problems

Thanks to Pete Bauman for his article summarizing this research. It pointed me in the is direction and informed my writing.

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