Menu

Management of Defoliating Insects in Nebraska Soybeans

Many defoliating insects may be found in Nebraska soybeans. Estimating defoliation levels in fields is the best way to decide whether it will pay to treat for these insects.

We saw several different insects in parts of Nebraska causing defoliation in soybeans in 2019. These included:

  • woolly bear caterpillars
  • green cloverworms
  • grassshoppers
  • bean leaf beetles
  • painted lady/thistle caterpillars
  • silver-spotted skipper caterpillar
  • Japanese beetles

Most of these insects are sporadic pests whose numbers vary from year to year and field to field. Some are migratory insects which do not overwinter in Nebraska, such as the thistle caterpillars and green cloverworms. Some are expanding their range in Nebraska, such as the Japanese beetle.

Regardless, when we have a mix of different insects feeding on soybean leaves, the best way to assess the need for insecticide treatment is to estimate the defoliation level from all insects present. In soybeans insecticide treatment is recommended when insects are present and damage is expected to exceed 30% defoliation in vegetative stage and 20% in reproductive stage soybeans. For more information see Managing Soybean Defoliators, NebGuide G2259. In addition to defoliation levels it is also important to identify which insect species are present, their size and abundance. This information will help you decide which insecticide product and rate should be used if treatment is needed.

Estimating defoliation can be difficult without practice. The chart below provides guidance on how to more accurately estimate defoliation in soybeans.

Estimating insect defoliation in soybeans. 1: remove leaves from top, middle and bottom of plant. 2: remove the highest and lowest defoliated trifoliate. Keep other leaflet. Repeat for the middle and bottom leaves on the same plant. 4: Repeat 1 - 3 on 10 more plants. 5: Repeat at 4 more locations and take average defoliation of all 40 leaves.
Process for sampling soybean leaves to assess defoliation. (Figure by Justin McMechan

Source: University of Nebraska CropWatch

Recent News

Federal Reserve: Observations on the Ag Economy- October 2020
10/22/2020

On Wednesday, the Federal Reserve Board released its October 2020 Beige Book update, a summary of commentary on current economic conditions by Federal Reserve District. The report included several observations pertaining to the U.S. agricultural economy. * Sixth District- Atlanta– “Agricultural conditions remained weak. While drought- free conditions prevailed in most parts of the District, some producers reported crop and […]

FAS Report: Corn Ethanol Production Booms in Brazil
10/20/2020

A report earlier this month from USDA’s Foreign Agricultural Service (FAS), Corn Ethanol Production Booms in Brazil, stated that, “Plentiful, and generally cheap, corn supplies in Brazil’s Center-West region have enticed investment in the corn ethanol sector over the last few years. There are currently 16 corn ethanol plants in the Center- West states of Mato Grosso, Goias, and Mato […]

Extended Drydown in Corn
10/20/2020

As fall is progressing, crop harvest is also occurring throughout the state. However, many producers are seeing slower than usual drydown in their corn fields this October. This may be in part due to how the weather conditions impacted corn growth and development this year. In many parts of Ohio in 2020, temperatures were near […]

Your browser is out-of-date!

Update your browser to view this website correctly. Update my browser now