Dung Beetles

Dung beetles are amazing insects that spend their lives mucking out your pastures. The adults use liquid contents for nourishment, and they lay eggs in small manure balls (brood balls) they bury in the ground. In the process, they serve as Nature's clean-up crew, getting rid of the manure "pat" and facilitating natural fertilization and aeration of the soil. Bill Clymer, PhD (parasitology) from Amarillo, Texas, says dung beetles are also the horseman's allies for controlling parasites that depend on manure as part of their life cycle.

In warm regions, beetles might be active year-round. There are more than 90 species of dung beetles in North America. Some are more active during warm seasons; others are more active during cool seasons. This means you might not have the same beetles working on manure in March and April as are active in July and August. Some are native; others have been imported. The native beetles are often a little smaller and tend to be more active in cool weather. Some of the more efficient ones, such as the Onthophagus gazella, were imported from Africa by the USDA.

"One of the O. gazella species that's about the size of your little fingernail will consume or bury more than 15 pounds of manure in its lifetime," says Clymer. "I have seen 20- to 30-pound manure pats from cattle totally gone within 24 hours."

Improved Pasture

"Dung beetles get manure off the top of the soil so you don't have the build-up that smothers out the grass," Clymer explains. "In many pastures, you see areas of tall grass where horses deposit manure. I used to think grass grew taller there because of the nutrients from manure, but it's also because the animals won't graze next to their own manure unless there's nothing else left to eat in the pasture." If dung beetles get rid of the manure piles, this creates more available pasture area.

One pastured animal produces about 12 fecal piles per day, or 4,300 fecal piles per year. Manure from a group of horses or cattle in a pasture may take 5-10% of each acre's available grazing. If none is recycled into the soil, a single animal can remove 2.5 acres of productive grazing each year. A herd of 50 animals can render 129 acres ungrazable in one year.

Without some way to remove manure, you not only lose the grazing area where manure is sitting, but also an area about 18 inches wide around it. These "roughs" continue to expand unless you do something about it. That's where dung beetles come in.

The beetles dissipate manure, and the birds that come looking for beetles to eat also tear manure piles apart and help spread them. Dung beetles can offset pasture loss tremendously. If there's an adequate population of beetles, they can bury 90% of the manure on pastures within a week. By contrast, the absence of dung beetle activity might mean manure will remain on the pasture for at least 16 weeks (and up to a year unless it's mechanically broken up).

Some species of beetles bury the manure, taking their eggs to different locations encased in little brood balls that serve as protection and nutrients for the larvae when they hatch.

"The tunnelers (beetles that bury brood balls) are actually the most beneficial," says Clymer. "They bury the manure under the pat, aerating the soil and fertilizing it. Their activity helps water percolate into the soil, enhances root penetration by pasture plants, and reduces contamination of water sources. If manure is buried instead of sitting on the surface, water run-off won't wash it away into the streams."

Up to 70% of the nitrogen in manure is lost if it isn't buried.

Although dung beetles might not completely eradicate the manure, especially a horse pile, their crawling through it helps various mites and bacteria disperse through the manure to help break it down. Clymer likes to call them "enviro-beetles" because of all the good things they do.

Natural Fly/Parasite Control

Dung beetles help control internal and external parasites of horses and cattle. The beetles' activity can reduce nematodes (internal parasitic worms) by as much as 90% and horn flies by 95%. In Australia, dung beetles are marketed for horn fly control. Even though beetles do not kill parasites, their dissipation of a manure pile disrupts or buries the parasites so they cannot complete their life cycle. Some of the flies and worms we constantly battle develop resistance to our pesticides over time. Mechanical and biological destruction of the manure pile is often more effective, especially if resistance is an issue, says Clymer.

Keep Beetles Healthy

Today there's increased interest in dung beetles because of the way they take care of manure and reduce flies and parasites. But sometimes our attempts to control parasites with chemicals hinder Nature's way of dealing with them--some types of dewormers and pesticides destroy dung beetles.

Horse and cattle owners who have used avermectin products for a number of years often discover that the "rough" areas in their pastures keep getting larger. Manure build-up in pens and corrals is more than it was in earlier years.

The avermectins do not kill adult beetles, but are toxic to the immature stages. Avermectins such as ivermectin and milbemycins (moxidectins) such as Quest are related, but moxidectin pesticides have been shown to be 64 times less toxic to beetles. With avermectins, manure might be toxic for immature beetles for several weeks after deworming. Since the beetles are attracted to fresh manure to lay their eggs, the eggs they lay in that manure might not survive--until the manure produced by that horse is no longer toxic.

If horses are dewormed regularly with avermectins, there are large blocks of time in which few dung beetle offspring will survive. Over time, this decimates the dung beetle population. If one of the avermectin dewormers is used, care should be taken to avoid treating during periods of heavy dung beetle activity.

"Some of the other dewormers like fenbendazole, oxibendazole, etc., don't have much impact on dung beetles. However, parasite resistance has been reported in horses in some areas," says Clymer.

Dewormers like Quest with moxidectin aren't as lethal to immature beetles--the horse's manure will be toxic to beetles for about three days following deworming. If you treat with an ivermectin product, however, the manure might be toxic to young beetles for two to six weeks. If you want to use ivermectin in a deworming program, the best time (for the least adverse effect on dung beetles) is when adults are inactive (not using the manure for reproduction), such as winter.

For instance, a late fall deworming after killing frosts (when many horsemen use ivermectin to control bots) will not affect your dung beetle population. If you use ivermectin only once or twice a year (such as late fall and very early spring, well ahead of warm weather), you will have the summer months (when dung beetles are most active) when they can safely reproduce.

If you've killed off your dung beetles, they can migrate to your place again from surrounding areas. Some species can fly up to 10 miles.

Although we still have to clean stalls, if we create a "dung beetle friendly" environment, the manure accumulation in our pens and pastures might be greatly reduced.


THREE TYPES OF BEETLES

  1. Dwellers live in manure and lay their eggs in it.
  2. Rollers (tumblebugs), usually larger beetles, are more active in southern regions; they lay their eggs in balls of manure to roll away and bury.
  3. Tunnelers dig below the manure pat to bury their manure-encased eggs.

WHERE DO YOU GET THEM?

While dung beetles have been commercially available in Australia for many years, few sources are available in the United States. Two insectaries in California (Beneficial Insectary, www.beneficialinsectary.com, and Rincon-Vitova, http://rinconvitova.com) are offering dung beetles for sale on a limited basis. If beetles are purchased, care should be taken to buy them from a reputable source and to obtain species that will adapt to your local environment. Each state might have different requirements for importation of insects. Beetles can cost $1 or more apiece, and Beneficial Insectary has a 200 minimum order.--Bill Clymer, PhD

About the Author

Heather Smith Thomas

Heather Smith Thomas ranches with her husband near Salmon, Idaho, raising cattle and a few horses. She has a B.A. in English and history from University of Puget Sound (1966). She has raised and trained horses for 50 years, and has been writing freelance articles and books nearly that long, publishing 20 books and more than 9,000 articles for horse and livestock publications. Some of her books include Understanding Equine Hoof Care, The Horse Conformation Handbook, Care and Management of Horses, Storey's Guide to Raising Horses and Storey's Guide to Training Horses. Besides having her own blog, www.heathersmiththomas.blogspot.com, she writes a biweekly blog at http://insidestorey.blogspot.com that comes out on Tuesdays.

Stay on top of the most recent Horse Health news with FREE weekly newsletters from TheHorse.com. Learn More