If you grow soybeans in Missouri, you know insect pests can eat into profits long before you notice visible damage. That’s why scouting isn’t just a good idea — it’s essential. According to the University of Missouri’s IPM team, a disciplined, methodical approach to scouting can help farmers identify problems early, apply treatments wisely and avoid unnecessary costs.
Here’s how to implement a proven scouting system that works.
- Scout Weekly — Even When Everything Looks Fine
The first rule of effective scouting is consistency. University of Missouri experts recommend weekly scouting in every soybean field, even if pest pressure seems low. Why? Because populations can quickly explode, and catching problems early makes all the difference.
Large fields should be divided into 40–50-acre blocks based on shared characteristics like planting date, variety or topography. Scout each block individually to get a clear, representative picture of pest activity.
- Use a Smarter Walking Pattern
It’s not just how often you scout; it’s how you move through the field. The University of Missouri advises walking in an X, U or zigzag pattern that takes you deep into the field. Starting at different points each time also prevents unconscious bias.
Critically, don’t just sample the field edge. Edge scouting gives an incomplete, and often misleading assessment, especially since pest populations can be higher at entry points and may not reflect what’s happening across the entire field.
- Use the Right Tools
Sweep nets and beat cloths are essential. The sweep net works best in dense canopy stages, while beat cloths are useful for early season and small plants. Both help determine insect populations accurately, which is crucial when deciding whether thresholds for treatment have been reached. - Know What to Look For and When
The pests that matter, and when they matter, will vary with the soybean growth stage. For example, defoliators like bean leaf beetles, Japanese beetles and green cloverworms are more of a concern in vegetative stages. Later in the season, pod feeders such as stink bugs become more economically damaging.
Accurate insect identification is key. The University of Missouri notes that misidentifying insects (or the cause of damage) can lead to spraying the wrong product or missing the real problem altogether.
- Use Economic Thresholds to Guide Decisions
The IPM program strongly recommends following economic thresholds before applying insecticides. This reduces costs, protects beneficial insects, and helps delay resistance. Thresholds are based on pest species, plant growth stage, and projected yield losses—not just visual damage.
For example:
- For defoliating insects, consider treatment when defoliation exceeds 30% in vegetative stages or 20% in pod fill stages.
- For stink bugs, the threshold is about 9 bugs per 25 sweeps in seed production soybeans.
- Tailor Your Approach Based on Field Conditions
Scouting isn’t one-size-fits-all. Differences in planting date, canopy density, soil type and even recent weather can all affect which pests show up and how quickly they spread. That’s why it’s critical to scout every field individually rather than assuming nearby fields share the same pest pressure. - Tap into Local Expertise
The Mizzou IPM program offers detailed pest guides, updated treatment thresholds and in-season alerts to help farmers stay ahead of emerging threats. Their field-tested recommendations are tailored specifically for Missouri conditions and are an invaluable resource during the growing season.
Want to dig into the full guide from the University of Missouri? Find it here:
https://ipm.missouri.edu/croppest/2024/6/soybean_ipm-iv/
This article is funded in part by the United Soybean Board
(Based on research and recommendations from the University of Missouri Integrated Pest Management program)