Predators of Insect Pests Thrive in "Live" Mulch

Living mulches help farmers improve soil quality and stave off weeds and erosion. But they may provide another benefit: habitat for beneficial predators that feed on destructive insects.

A two-year study by Agricultural Research Service (ARS) and Iowa State University scientists—described in this month's issue of Environmental Entomology—lent weight to this long-suspected hypothesis. The research showed that predators killed many more pupae of the costly European corn borer in fields hosting the living mulches than in mulch-free plots.

Unlike other types of cover crops, living mulches are not eliminated before planting of the main crop.

Entomologists Jarrad Prasifka and Richard Hellmich at the ARS Corn Insects and Crop Genetics Research Unit in Ames, Iowa, and their collaborators used separate plantings of alfalfa and of kura clover, a persistent forage of west Asian origin.

The researchers found increases in the number of predators and in the number of pupae the predators consumed in plots holding a rotation of corn, soybean and forage crops.

The predators, mostly carabid ground beetles and arachnids, consumed pupae used as "sentinel prey"—that is, prey placed in the field to measure predator activity.

Within the living mulches, predatory insects killed 66 percent of the borer pupae planted in corn—a 51 percent increase over nonmulched control plots—and 65 percent of the pupae in soybeans, 13 percent more than in the control plots.

Scientists in the Ames unit are conducting similar studies targeting other insect pests.

Living mulches may not provide sufficient pest suppression when used alone and often need to be suppressed themselves to prevent competition with the main crop, according to Prasifka. But they can be an important component of an integrated pest management program.

Also, studies have shown that using legumes as living mulches may reduce the need for fertilizer by providing nitrogen to the main crop. It may also lead to yields equaling or exceeding those produced through conventional methods.

ARS is the U.S. Department of Agriculture’s chief scientific research agency.