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First look for pests in soybeans

Soybean Watch: Bean leaf beetles, slugs and voles often make early appearances.

Tom J. Bechman, Midwest Crops Editor

May 24, 2024

3 Min Read
A slug on the palm of a hand
CAUGHT IN THE ACT: Agronomist Steve Gauck holds a slug he discovered after first noting leaf damage and a cut stem. Tom J. Bechman

Will this be a year with slug problems in soybeans? “Slugs like moist conditions, especially if there is residue in the field, although sometimes there seems to be little rhyme or reason to when and where they appear,” explains Steve Gauck, regional agronomy manager for Beck’s, Greensburg, Ind. Beck’s sponsors Soybean Watch ’24.

“Pull back plants and look for slugs at ground level or in residue,” he says. “They’re small, slimy and feed on anything from cotyledons to larger leaves.”

Unfortunately, once you find them, there’s little remedy for slugs, Gauck says. “They tend to quit feeding and move deeper into the soil once temperatures warm up, but there are no guarantees,” he says. “We have found them as late as the first of July in Soybean Watch fields.”

The Soybean Watch project reports observations from one soybean field in south-central Indiana. This field was planted May 12. Hopefully, these observations will relate to what happens in your fields.

Insect feeding

Check stands of young soybeans for bean leaf beetle feeding. Reports of feeding have already surfaced.

“We could see slight to moderate leaf feeding from the overwintering population of bean leaf beetles this year,” notes Chad Kalaher, a Beck’s field agronomist covering northeastern and eastern Illinois. “These tend to occur more frequently in fields with high residue and where no insecticide seed treatment was used. Defoliation levels, however, are not usually high enough from this insect early to economically justify an insecticide application.”

Related:Assess soybean stands, make decisions

In fact, the Purdue University Corn and Soybean Field Guide doesn’t recommend an insecticide treatment for bean leaf beetles unless defoliation from V1 through R2 stages is above 30%. This insect has two generations per year. The more critical time for potential damage and yield loss occurs at later growth stages. From R3 through R5 stages, the Purdue guide recommends treating if there is more than 10% defoliation.

From the field

Early planting activity was interrupted with stretches of rain showers. This is producing a checkerboard pattern of planting progress and crop emergence across the Midwest. Here is a closer look:

In Illinois. Early progress stalled for three weeks with no wheels turning in west-central Illinois. Growers capitalized on a narrow window over Mother’s Day weekend before rains returned. Many soybeans are planted with some up, but lots remain to be planted. — Holly Spangler, Prairie Farmer editor

In Iowa. “In Southeast Iowa, we were just getting dried out, with a little planting activity over Mother’s Day weekend. Then showers moved through again.” — Greg Shepherd, Beck’s field agronomist

In South Dakota. “We’re not really looking for anything disease- or insect-related yet. We only have about 20% of soybeans planted, waiting for it to dry.” — Jerry Mathis, Beck’s field agronomist

In Ohio. Ohio State University agronomists Osler Ortez and Laura Lindsey report a difference in bean leaf beetle feeding in Battle of the Belt field trials comparing planting dates. At the western Ohio location, bean leaf beetle damage was found in the March 25 planting at V1 stage, but was minimal in the April 16 planting at VC stage. — As reported in C.O.R.N. Newsletter, edition 2024-14

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About the Author(s)

Tom J. Bechman

Midwest Crops Editor, Farm Progress

Tom J. Bechman became the Midwest Crops editor at Farm Progress in 2024 after serving as editor of Indiana Prairie Farmer for 23 years. He joined Farm Progress in 1981 as a field editor, first writing stories to help farmers adjust to a difficult harvest after a tough weather year. His goal today is the same — writing stories that help farmers adjust to a changing environment in a profitable manner.

Bechman knows about Indiana agriculture because he grew up on a small dairy farm and worked with young farmers as a vocational agriculture teacher and FFA advisor before joining Farm Progress. He works closely with Purdue University specialists, Indiana Farm Bureau and commodity groups to cover cutting-edge issues affecting farmers. He specializes in writing crop stories with a focus on obtaining the highest and most economical yields possible.

Tom and his wife, Carla, have four children: Allison, Ashley, Daniel and Kayla, plus eight grandchildren. They raise produce for the food pantry and house 4-H animals for the grandkids on their small acreage near Franklin, Ind.

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