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Behold The Humble Dung Beetle

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Until you step in one, it s easy to ignore cow-pies.

They may be little more than stinky landmines to some, but for AAFC Lethbridge insect biocontrol researcher Kevin Floate, cow-pies are host to such an array of fascinating insect activity that he can t stay away from them.

But only in summer, he said, in a recent telephone interview. I m not crazy.

Of particular interest to Floate are the dung beetles, just one of hundreds of fly, wasp and fungi species that begin colonizing the pizza-sized piles of water, masticated and partially digested plant matter within seconds after it hits the ground.

Interestingly, the majority of the 15 species of dung beetles that inhabit Canada s cow-pies originally hailed from Europe, and are of a type that don t degrade the dung very quickly, often taking weeks to munch through one.

There s another group of dung beetles that can break down a cow-pie in days, said Floate. They are present on the Prairies, but the problem is that they are only active for a short period during the summer, and they prefer sandy soils.

With that in mind, Floate and his colleagues have in recent years brought in two species from south of the border to speed things up.

Digitonthophagus gazella, which hails from Florida where it was deliberately introduced from overseas to control dung, succumbed to the cold weather in the first year.

Onthophagus taurus, which may have hitched a ride to the same state on military equipment brought back from Germany, now ranges as far north as Michigan and New Jersey, and continues to expand its territory.

It did slightly better at overwintering than its counterpart in Alberta, but it seemed to dwindle off over time rather than thrive.

Why the need for speed?

Floate said that there are two main reasons for wanting to break down cow-pies more quickly. First, fresh ones are a breeding ground for pests such as horn and face flies, which can affect beef production by annoying the cattle.

Second, the longer cow-pies linger on the pasture, the more they blot out grass production just by taking up space.

Also, cattle don t like to graze the rank grasses that grow nearby, which means that up to five times as much area as that taken up by the cow-pie itself is lost to grazing, in some cases for months or even years.

If we can get dung beetles to rip apart those cow-pies so that it dries out more quickly, the maggots inside the pies don t have time to turn into adult flies, said Floate.

Intensive graziers avoid this problem, he noted, first by rotating the cattle out ahead of the flies with frequent pasture moves, and also by using heavy stocking densities to trample the pies into the ground.

Insect activity, such as breeding and feeding, and species diversity is greatest from mid-May to late June.

But by late July to early August, the fun stops with the advent of summer s blazing heat, and dry weather creates an insect-impenetrable crust.

Cooler, wetter temperatures in early fall lead to a resurgence of dung beetle activity, he added.

What s the best way that a rancher can encourage dung beetles to set up shop?

One way to roll out the red carpet is to avoid using ivermectin-type anthelmintics in spring because the residues may linger in cow-pies and affect dung beetles for up to three weeks after treatment.

For some fly species, that effect could last up to three months.

If it s a pest fly breeding in the manure, those residues could be good. But the downside is that if the residue is killing pests, it s probably affecting the dung beetles as well, said Floate.

If cattle are treated with a pour-on in fall, it would make no difference to the dormant dung beetles.

In any case, due consideration should be given to the potential effect on a ranch s bottom line. In dry climates like southern Saskatchewan and Alberta, parasite loads on grass are typically very low anyway.

Rather than automatically applying ivermectin for parasite control, ask yourself if you really need to, said Floate.

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