Bean Leaf Beetle (also feeds on pods)

Other Information:

Small (1/4"), yellow-buff to reddish beetles, four distinct black spots on their back. Some lack spots, but all color forms have a black triangle at the base of the wing covers. Bean leaf beetles attack soybeans throughout the growing season. Overwintering adults colonize early-emerging soybean fields, but beetle feeding on cotyledons and unifoliolate leaves does not reach economic threshold. One generation in north MN and two in south MN per year.  Larvae feed underground on soybean roots and nodules, but this feeding doesn't affect yield. Adults feed on soybean leaves in July and August.  Adults also feed on pods, affecting seed development and allowing disease entry. These beetles should be treated if damaged pods exceed 10%, or if adults exceed 0.5 per plant, during pod-fill.  Heavy populations should be watched closely and treated aggressively if pod clipping is noted

Grasshoppers

Other Information:

Grasshopper populations develop during dry springs following long, warm autumns.  With moderate or high moisture, fungal diseases keep grasshopper populations in check. Grasshoppers prefer laying eggs in untilled soil (i.e. roadsides and ditches). Damage first occurs at the margin of fields.  An exception is in fields planted last year with soybean or alfalfa. Grasshopper nymphs look very much like adults, but lack fully developed wings. Grasshoppers feed on leaves and, as soybeans mature, on developing pods

.

Green Cloverworm

Other Information:

This migratory moth is common throughout the soybean-growing areas of the eastern United States and the Great Plains, but seldom reaches pest status. The caterpillar is green with white and typically has two generations per year. Because it attacks early in the season, however, plants usually compensate for foliage loss before pods are set. Green clover worm can be a valuable food source for beneficial insects and diseases. This reservoir of beneficials often controls pests of more economic importance later in the season.

Japanese Beetle

Other Information:

The Japanese beetle has a wide variety of plant hosts and will attack soybeans both early and late in the growing season. A soybean-feeding variant does not occur in Minnesota at this time.  Adult beetles feed on foliage, skeletonizing the leaves. They are long, have a hard shell, are metallic green, and have bronze-colored wing covers. Small white squares (actually tufts of hair) are visible around the outside edge of the wing covers.

Potato Leafhopper

Other Information:

Very small (~1/8"), wedge-shaped insects. They are bright green, quick moving, and have piercing/sucking mouthparts. Feeding causes localized stippling, yellowish to reddish-yellow discoloration of leaves (especially at the tips), leaf crinkling and cupping. This injury may appear similar to herbicide damage. Extensive feeding damage results in stunted plants. The thick pubescence on soybean leaves tends to prevent this small insect from getting close enough to implant its mouthparts. However, young plants without heavy pubescence are vulnerable to leafhopper attack. Stressed plants are also more vulnerable to injury from potato leafhopper than are healthy plants. Soybean fields adjacent to alfalfa fields should be considered at a greater risk from potato leafhopper infestation due to movement when alfalfa is cut.

Saltmarsh & Woolybear Caterpillars

Other Information:

Hairy, robust caterpillars; may be white or multicolored, solid, or banded. Often feed in the upper canopy where they are noticeable, so populations are frequently overestimated. Smaller larvae tend to feed in the lower canopy or on the underside of leaves, so early infestations can go unnoticed. This insect is only an occasional problem in Minnesota, except for drought years.

Two-spotted Spider Mites

Other Information:

In most years, spider mite populations are kept in check by fungal diseases and predators. Both mortality factors require cooler temperatures and higher humidities. In very warm, dry years spider mite populations can rapidly increase and cause widespread damage through soybean fields.  Early infestations will kill soybeans, while later infestations cause premature senescence and reductions in yields up to 40%-50%. Soybeans planted next to alfalfa are at high risk during favorable mite conditions, and should be scouted first. Look for stippling and bronzing of soybean leaves. Fully grown adult mites will be barely visible to the naked eye on the underside of leaves, while younger stages will have to be observed with a hand lens. Eggs will hatch in several days, and infestations may begin again, so continued scouting is recommended. Be advised that if an outbreak has occurred, subsequent rain alone may not solve the problem of spider mite infestations, because the fungal diseases which attack them will be too late.

Thistle Caterpillars

Other Information:

The caterpillars of the painted lady butterfly rarely cause problems in soybeans unless an unusually large spring migration of the butterflies occurs from the U.S. desert Southwest or Mexico. The caterpillars are commonly found on thistles, but will also attack early vegetative soybeans.  The larvae (up to 1.5 inches long) feed on the top leaves and web them together with silk.  Their appearance is quite distinctive. The body is black with yellow spots and has numerous multi-pronged spines. Treatment is recommended if defoliation exceeds 50%.