Home / Guides / Field Crops, Grains & Oilseeds
Field Crops, Grains & OilseedsField Crop Pest Scouting Calendar
Good scouting follows the crop, not the calendar. The schedule you build should tie each field visit to a growth stage and to the weather that tends to bring problems.
Key points
- Tie scouting visits to growth stages and weather, not just the date.
- Scout before planting and after emergence as well as during the season.
- Walk a pattern, sample several places and record the stage and date.
- Compare findings with extension thresholds and follow the label for any treatment.
- Keep field records and use them to plan next year.
How often should you scout field crops?
Extension programs generally recommend regular visits through the season, with more frequent checks during stages when the crop is most vulnerable and when weather favors pests. A weekly walk is a common baseline, and many crop advisers adjust it to every few days when pressure is building and to less often when the crop is stable.
Because pest timing depends on temperature and moisture, your own records are the best guide. Note when each problem showed up in each field and use those dates to plan next year's visits. Your state extension service often publishes pest alerts and scouting reports you can follow.
If you hire a crop adviser, agree on a schedule and on how reports will be shared, so that findings reach you in time to act.
What should you look at before the crop emerges?
Scouting begins before planting. Walk fields in early spring to note winter annual weeds, residue, standing water and signs of last year's disease. Check cover crop growth and decide whether termination timing is on track.
After planting, check emergence and stand about a week or two later by digging seedlings and looking for poor root growth, seed damage or uneven depth. These checks often reveal problems before they show up as bare spots.
- Dig and check seedlings, do not just look from the truck
- Note weeds present at planting
- Record stand counts by area
- Mark problem spots on a field map
How does growth stage guide the scouting plan?
Different pests matter at different stages. Early season often means stand establishment, soil insects and early weeds. Mid season may bring foliar disease, leaf-feeding insects and weed escapes. Late season includes pod and ear feeders, lodging and standability.
Learn the growth stage system for each crop, such as V and R stages in corn and soybeans, and use it when you record observations. Extension thresholds and advisories are almost always written by stage.
Weeds are staged too. Small weeds are easier to deal with than large ones, and labels often limit application to specific weed sizes, so check the weed height and the label together.
How do you scout properly?
Walk a defined pattern across the field instead of looking at the edge. Sample several places and note the number of plants checked. Look at the upper and lower parts of plants, and the undersides of leaves where appropriate.
Take photos and notes with the date, field and growth stage. If you are not sure of an identification, send a clear photo or a sample to your county extension office or a plant diagnostic clinic. A wrong identification can lead to a wrong decision.
What do you do when you find a problem?
Compare what you see with the economic threshold published by your state extension service, if one exists for that pest and crop, and confirm that the crop stage fits. Not every problem needs treatment.
If treatment is considered, ask your extension office or a licensed applicator for current recommendations. The label is the law, including pre-harvest intervals and re-entry rules, and applicator licensing varies by state. Protect pollinators by avoiding application during bloom and when bees are active.
How do weather and field history change the plan?
Warm, humid, wet conditions favor many foliar diseases, while dry spells can raise some insect problems. Field history matters too, since residue, rotation and previous problems influence what to expect.
Use the National Weather Service forecast and local extension alerts to adjust the schedule in the days ahead.
What mistakes weaken a scouting program?
The most common mistakes are scouting only the edges, waiting too long between visits and failing to record what you saw. Another is relying on memory, which fades by the next season.
A further mistake is acting on a single observation without checking thresholds or the crop stage. Many problems do not need treatment, and unnecessary applications cost money and can harm beneficial insects and pollinators.
A single page per field with date, stage, what you found and what you did is enough. Add photos. At the end of the season, review the records with your crop adviser and highlight patterns. Those records are the most reliable guide for building next year's scouting calendar.
Sources and further reading
Last reviewed: November 2026. Educational information, ranges only. Confirm timing with your county extension office.