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During the second session of Soybean Summit on February 17, I had the opportunity to learn from Dr. Nick Seiter, who presented “Insect Management: What did we learn in 2020?” If you were unable to attend this session, I would like to provide some insight on the topic. I hope after reading this blog you will be motivated to watch the full presentation here: Insect Management: What Did We Learn in 2020? - YouTube

Dectes Stem Borer

This insect has caught the eye of several farmers and agronomists, specifically in Southern Illinois. 

Adults: Adults do not cause active damage to the soybean plant. The adults will be active during June and July and will lay eggs in the petiole of the soybean plant.

Larva: Larva will hatch and feed on the pith of the soybean stem. This feeding does very little to impact the yield or performance of the soybean. However, by eating the pitch, the overall integrity of the stem is aggressively compromised.  

Damage: True yield and economic damages come from having a large population of soybean with lodging damage that can be properly harvested.   

Overwinter: The larva will eventually make its way to the base of the stem where it will overwinter.

Management: Adults can be active for six to eight weeks and one insecticide application would not completely prevent all adults from laying eggs. This option is not very economical. Once larva is in the stem, there is no treatment. However, once the issue has been determined, it’s important to manage for a timely harvest.

Bean Leaf Beetle

In most years, bean leaf beetle (BLB) is considered an occasional pest, however in 2020, several regions in Illinois (central, northern, eastern) experienced heavy populations that required a rescue treatment and also damaged yields. 

Adults: A given soybean crop can experience two generations of adults in each crop. 

• The first adult will feed on the recently emerged soybean plant.
• The second adult will feed on the pods during reproductive stages.

Damage:

• Feeding on leaf area, which can minimize photosynthetic material.
• Can infect a soybean plant with the bean pod mottle virus.
• Feeding on the outer tissues of the pod, which will allow moisture into the pod that can impact the seed quality.

Overwinter: The second adult in a given crop will overwinter in leaf material and tree lines.

Management: Seed treatments with an insecticide can provide suppression from the adult feeding at early vegetative stages. The second adult can be controlled with an insecticide tank mixed with a fungicide application during the R3-R4 reproductive stages. 

For more information on this topic, you can view Dr. Seiter’s entire presentation here. You can also view all Soybean Summit sessions here.