May 25, 2012

We have received several reports of millipedes damaging soybeans in southeastern and south central Nebraska. A sample submitted to the UNL Plant Pest Diagnostic Clinic was identified by Jim Kalisch as a garden millipede, Oxidus gracilis.

Millipedes have been reported damaging cotyledons and stems prior to emergence of the seedling, and in some cases killing the seedling. In many cases these fields were planted into corn residue from last year. Some of the damaged fields had a neonicotinoid seed treatment which apparently did not provide high levels of control of millipedes. This is not surprising as millipedes are not listed as a pest controlled by neonicotinoid seed treatments (e.g. Cruiser, Poncho, Gaucho).

Millipedes are encouraged by high levels of organic matter on the soil surface. It is possible the mild winter has also led to higher than usual numbers. Their usual feeding habits are on decaying organic matter.

There is little information on chemical control efficacy against millipedes in crops. In at least one case, multiple applications of a pyrethroid insecticide had little apparent effect. Usually millipedes move deeper in the soil as soil surface temperatures increase and soil surface moisture decreases.

At this time probably the main decision to make is whether there is enough damage to warrant replanting.

Bob Wright
Extension Entomologist