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Cover Crops Promote Beneficial Insects
by LuAnn Rolling, District Conservationist

As we launch into the crop growing season producers are beginning to think about crop pests like insects. All good producers will use an integrated pest management system, IPM, that includes a variety of tactics to control pests. One control method that may go unnoticed is the introduction of cover crops.  

In an interview with No-Till Farmer magazine in their May 2021 issue, Justin McMechan, Assistant Professor for Crop Protection with University of Nebraska Extension, says, “A large majority of insecticides are very broad spectrum, meaning they kill a lot of different kinds of bugs.” He adds that pesiticides cost money and generally wipe out the system, including the good bugs like spiders, carabid beetles, etc., and leave the system blank for something new to come in that’s potentially worse – like black cutworms or common stalk borer.

McMechan says that cover crops provide potential preventative management by increasing the ecosystem and reducing potential pest pressure.  He notes that insects like spiders or black beetles are often attracted to areas that increase their ability to hunt. “For example, rye often has a lot of aphids in it.

Those aphids are a food source for beneficial insects.” This is a significant advantage because it means there is a potential for an abundance of predators in the system at a vulnerable time moving into the next cash crop.

In a May 2018 article in Soil Health, Eric Mader, a pollinator program co-director for the Xerces Society and formerly with extension at the University of Minnesota, says that an insect group that provides perhaps the most direct impact on corn-and-soybean profitability are common ground beetles, which live their entire lives either in or on the soil.

“Ground beetles are the cheetahs or lions of the soil surface, as they can live for years and are incredible predators of pests like slugs,” Mader says. “These are running hunters on soil surfaces. They’re known to consume more than their own body weight in prey on a given day, often killing more prey insects than they can eat.”

Mader adds that one more unsung group of ground beetles are seed-feeding ground beetles. “They exhibit a very strong preference for feeding on seeds of many plants considered as agronomic weeds, with lambsquarters topping the list” he says.

Depending upon the species, a single, seed-feeding ground beetle can feed on dozens to hundreds of seeds over a 48-hour period, Mader says. Aggregated over large populations of ground beetles on an acre of cropland, their impact can be significant.

Mader cautions no-tillers about becoming too reliant on systemic pesticide groups, such as the growingly popular neonicotinoids in seed treatments and foliar sprays.  “The insecticides are spreading out into larger environment because they’re mobile in water and they can last for multiple years in the soil.”

“Over-reliance on these is contrary to the fundamental principal of an integrated pest management program, which tells us we should only use insecticides when there’s a documented pest outbreak. We shouldn’t be using pesticides prophylactically,” he says.