Monitor Populations and Manage Thresholds with an Integrated Approach
By staying informed about insect populations, managing economic thresholds, and planning pest management activities in advance, you can have a better handle on the pest pressures that threaten your yields.
Get migration notifications and more with Insect Forecast, available April through September within the agIndex app. Learn more about this free app.
Common Yield-Limiting Pests
Mild winters generally promote higher densities of Japanese beetles and early plantings in these conditions can lead to potential economic loss. Adult Japanese beetles are shiny and metallic green with brown wing "covers". Approximately 0.6" in length, they have a row of six bunches of white bristles along the side of their abdomen.
Scout flowering fields for the presence of Japanese beetles and the extent of defoliation. Estimate the percent defoliation on randomly selected leaves in at least five different areas of the field. Insecticide treatments should be considered when beetles are present and defoliation reaches 30% before bloom or 20% between bloom and pod fill.
Soybean aphids are small, soft-bodied, pear-shaped insects that vary in color from yellow to green with black cornicle "tailpipes" on the back of their abdomen. Aphids feed in colonies on the leaves and will cause leaves to turn yellow or wilt.
During vegetative growth, examine new leaves, petioles and stems in the upper and lower crop canopy. Insecticide application timing is critical and should be done from R1 to R3 (beginning flowering to beginning pod) based on observations from several plants throughout the field.
Two-Spotted Spider Mite
Spider mites are difficult to spot with the naked eye because of their small size. Spider mites have piercing, sucking mouth parts that take nutrients from plant leaves. High populations can decrease yield potential by reducing photosynthesis, increasing water stress and increasing soybean seed shattering potential at harvest.
Because spider mites are barely visible, scout for them by shaking a plant over a white sheet of paper. If you see moving specks, then spider mites are present. If the spider mites are present and you have hot and dry conditions forecasted for your area, then you should consider an insecticide treatment.
Bean Leaf Beetle (Spotted Phase)
The bean leaf beetle has two generations that can feed on soybeans throughout the growing season. Bean leaf beetle is distinguished from other similar beetles by the presence of a black triangle on its back, behind its head. The bean leaf beetle can cause feeding injury to the plant and also carry vector viruses including the bean pod mottle virus.
When soybean fields emerge, scout weekly for bean leaf infestations. This is important because early planted soybeans may attract overwintering bean leaf beetles. Counting the bean leaf beetles directly on the plant is the preferred method to estimate beetle numbers during the early stages of soybean development (VC to V2 growth stage). Measure 10 feet of row and count the number of beetles. Repeat this process in at least four other locations in the field. If beetle densities exceed 16 per row foot in the early seedling stages, VC or V1, or 39 per row foot at stage V2+, then economic injury is possible and an insecticide treatment should be considered.
Soybean Cyst Nemotode
The soybean cyst nematode is one of the most damaging pests to soybean crops throughout the U.S. Soybean cyst nematode adult females are white to yellow in color, lemon shaped and the size of a pinhead. Soybean cyst nematode can never be eliminated from a field and is commonly mistaken for other cropping problems such as soil compaction or iron chlorosis, so it is important to manage the problem appropriately.
To evaluate soybean cyst nematode during the growing season, identify females on soybean roots by pulling roots out of the ground. To accurately determine soybean cyst nematode populations, take a soil test in the fall prior to planting. If the soybean cyst nematode egg counts are 2,000 or less per 100 cubic centimeters of soil, when coming out of long-term continuous corn, a soybean product susceptible to soybean cyst nematode may be an option. For counts from 2,001 to 12,000, select a soybean product with moderate resistance. And for rates exceeding 12,000, this field should not be considered for soybeans.
The kudzu bug has also been commonly referred to as bean plataspid, lablab bug, and globular stink bug (although, technically, it is not classified as a stink bug). This insect is native to Asia and was first discovered in the United States in 2009 in nine northeast Georgia counties.
Early-planted soybeans may be at greater risk of infestation than later-planted soybeans due to timing of migration. Adult insects can be found primarily on the main stem near nodes. Small nymphs have been observed feeding on leaf veins. Eggs are primarily observed on the underside of leaves. Damage occurs to the soybean plant when the kudzu bug uses its piercing-sucking mouthparts to remove plant sap.