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Pest, Disease & Weed Timing CalendarsMite Monitoring Calendar
Mites are not insects, but they are scouted like them. Heat and dry weather speed them up, so your calendar should follow the forecast.
Key points
- Mite populations explode in hot, dry, dusty conditions, so follow the forecast.
- Use a hand lens, look for stippling and webbing, and check leaf undersides.
- Protect predators by avoiding unnecessary broad spectrum treatments.
- Reduce stress and dust and keep records of each check.
What makes mites a timing problem?
Spider mites are very small arachnids that feed by piercing leaf cells. In warm weather they develop quickly, with several generations in a season. A light infestation can become a heavy one in a short stretch of hot, dry days, and heavy infestations cause bronzing, leaf drop and fine webbing.
Because the build-up is fast and the animals are tiny, regular scouting from late spring through summer matters more than any single check. Generation time shortens as temperatures rise, which is why a field that looked clean on Monday can show damage by the following week.
Different mites feed on different plant parts. Rust mites and broad mites are even smaller than spider mites and show up as bronzing, curling or distorted growth, so a hand lens of higher magnification may be needed.
How do you scout for spider mites?
Look at the undersides of leaves with a hand lens. Stippling, which appears as many tiny pale dots on the upper leaf surface, is an early sign. Webbing on leaf undersides and between stems shows a larger infestation. Tapping a leaf over white paper dislodges mites that show as tiny moving specks.
Check the lower and middle canopy first, and check plants along dusty field edges and roads, where mites often begin. Mark the plants you checked with a flag so the next visit starts on the same plants and shows true change.
Weed control around crop edges matters, because mites often move from drying weeds onto crops as weeds are cut or dry down.
- Hand lens on leaf undersides
- Stippling on upper surfaces
- Webbing in heavy infestations
- Tap test over white paper
When should you scout most closely?
Increase checks during hot, dry stretches and when plants are drought stressed. Dust also favors mites. Mites tend to decline in cool, wet weather, though they can persist on protected plants. In greenhouses and high tunnels the conditions can favor them through much of the year.
Corn, soybeans, beans, tomatoes, strawberries and tree fruit can all host spider mites. Other mites, such as rust mites and broad mites, affect particular crops, so check your extension pest list.
Check your irrigation scheduling too: plants with even water supply handle feeding better, and local water rules should guide when and how much you irrigate.
How do thresholds and natural enemies fit in?
Extension thresholds for mites vary by crop and stage, often based on the proportion of leaves with mites or on leaf damage. Check the value for your crop from your state extension service.
Predatory mites, lady beetle larvae and other predators help control spider mites. Broad spectrum insecticides can kill these predators and cause mite outbreaks, a reason to choose products and timing with care and to follow local advice.
What cultural steps lower mite pressure?
Reduce plant stress with steady irrigation scheduled according to local rules, and limit dust on roads near the crop. Remove weeds that can host mites, particularly around greenhouse and tunnel edges. Clean tools and inspect new plants before they enter a protected space.
A water spray on small garden plants can reduce numbers in a home setting.
What should your mite log say?
Record the date, the crop stage, recent weather, where you looked and what you saw. Note the percentage of leaves with mites or stippling if your threshold uses it.
For chemical decisions, remember that the label is the law, pre-harvest intervals apply, pollinators must be protected and applicator licensing varies by state. Your extension office can give current local recommendations and resistance management advice.
What does a worked example look like in a bean field?
For example, a grower with a bean planting notices dusty edges during a hot, dry week. A check of ten plants shows pale stippling on a few lower leaves, and a hand lens reveals a handful of mites on the undersides. The grower records the percent of leaves affected, adds a note about the forecast and plans another check in three or four days instead of waiting a week.
On the next visit, the stippling has moved up the plant and predators are present. The grower compares to the extension threshold and calls the extension office to discuss options before conditions get worse.
The lesson is that frequency should follow the weather. A hot dry week is a signal to shorten the interval between checks.
Sources and further reading
Last reviewed: November 2026. Educational information, ranges only. Confirm timing with your county extension office.