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Pest, Disease & Weed Timing CalendarsWeed Scouting Calendar
Weeds are easiest to deal with in the first few weeks, which means the calendar that matters is a series of short, regular field walks.
Key points
- Scout before planting, soon after planting, and before and after each control step.
- Use shorter intervals in early crop stages and after rain or warm spells.
- Keep field maps and notes to spot patches and escapes.
- Check results after a pass instead of assuming it worked.
When should weed scouting begin?
Start before planting. Walk fields to see what has emerged, what winter annuals or perennials are present and where problem patches sit. That information helps you pick a pre-plant approach and sets a baseline for the season.
Then scout shortly after planting and again before and after any control step. Extension specialists repeatedly point out that scouting after an application is as important as before it.
After harvest, a brief walk also shows how fall-germinating weeds are starting. Winter annuals that get established in fall are much easier to deal with in the following spring if you know they are there.
How often should you scout?
During the early crop stages, weekly walks are a reasonable pattern, with extra checks after rain or a warm spell that triggers emergence. Once the crop canopy closes, intervals can lengthen, but keep looking for escapes that will set seed.
For example, if your last planting went in during a warm week, the first walk a week later may find weeds just emerging, which is exactly when control is easiest.
Weather should push your calendar. A long wet spell often delays field work, and weeds can grow past an ideal control size in those days. A quick check as soon as the weather clears tells you how far behind you are.
What should you record?
Write down the species, the approximate size or growth stage, the density and where in the field they sit. Note whether the crop is competing well. A simple map is helpful for spotting patches that grow each year.
Record anything that survived a control pass. Survivors are the clue to missed timing, poor coverage or resistance, and you want that information early.
Tag any spots where you saw a species you cannot identify. Send clear photos of the whole plant, the leaves and any flowers or seedheads to extension for help.
- Species and relative size
- Patch location on a sketch map
- Crop stage on that day
- Weather before and after the last control step
How do you check how well control worked?
Return several days after a herbicide or cultivation pass and compare. Different products and tools show results over different periods, so ask your extension office how long to wait. If a species is still healthy after the label's expected period, take photos and contact extension or your adviser before repeating anything.
Do not respray in a hurry. Label limits on number of applications and intervals apply, and repeated pressure on the same weeds can speed resistance.
Use the same method each time so results compare from week to week. Consistent counting, even if rough, beats a detailed one-off survey.
What about the end of the season?
Late scouting catches escapes that will drop seed and shape next year's weed pressure. Mark the patches, remove or manage them as local advice suggests and note them on your map. Seed that never returns to the soil is the cheapest control you have.
Combine this with harvest and equipment cleaning habits, since machines move seed between fields.
Some farms assign scouting to one trusted person so the standard stays steady. Whoever does it, the notes should be written and shared, not kept in memory.
What does a scouting walk look like in practice?
Plan about the same number of stops per acre each time, and cover edges, wet spots, headlands and field entrances, where weeds often arrive first. Stop, kneel and look at the ground, not just over the canopy. Small seedlings hide under crop leaves.
Carry a notebook, a phone for photos and a simple ruler or the crop growth stage chart. Weed height and crop stage often decide whether a control option is still allowed under the label.
How do you scout organic or small plantings?
Smaller plantings can be walked row by row. Check between plants and along the drip lines and mulched edges, where weeds root easily. Hand weeding is most effective while weeds are tiny, so a short check every few days during the early weeks beats one long weeding session.
Record patches of perennial weeds separately. They need a different plan from annuals, and extension can help you choose methods that suit your crop and certification rules, if you have one.
Sources and further reading
Last reviewed: November 2026. Educational information, ranges only. Confirm timing with your county extension office.