Home / Guides / Pest, Disease & Weed Timing Calendars
Pest, Disease & Weed Timing CalendarsWilt Disease Calendar
Wilt fungi live in the soil for years, so the calendar that works is mostly about decisions made before planting and sanitation after the crop is finished.
Key points
- Wilt fungi persist for years, so plan rotation and resistance well before planting.
- Resistant varieties are race specific, so read the codes.
- Confirm a suspected wilt with a lab before changing your whole plan.
- Sanitation after harvest and clean transplants slow the spread.
Why do wilt diseases need a calendar at all?
Verticillium and Fusarium wilts are soilborne. Extension sources describe survival structures that stay in soil and plant debris for several years, and in the case of Verticillium, potentially a decade or longer. Once a field is infested, you cannot clear it in one season.
That is why timing matters in the off season. The goal is to keep the fungus from building up, choose plants that tolerate it, and avoid stress that makes symptoms worse.
Think of the calendar as three seasons: the planning months, the growing months and the cleanup months. Each one has a short list of tasks, and skipping one makes the next harder.
What should you do before planting?
Start with records. Mark which beds or fields held tomatoes, peppers, potatoes, eggplant, melons or other wilt hosts, and which ones showed wilting last year. Select resistant varieties where they exist. Seed catalogs and extension variety trials list resistance by letter codes for the races involved, and a variety resistant to one race may not resist another.
Raised beds that drain well also help, since saturated soil encourages root infection. A soil sample for nutrient levels is a good time to ask extension whether a wilt test makes sense for your site.
How do you spot wilt during the season?
Early signs are wilting on hot afternoons with recovery overnight. Over days the wilting becomes permanent. Cut a lower stem near the soil and look for brown discoloration inside. Yellowing that starts on lower or one side of the plant is a typical clue.
Because several problems mimic wilt, including root rot, stem borers and plain drought, send a sample to your diagnostic lab before pulling a whole planting. Diagnosis matters because it decides what you do next season.
If you see wilting in only one corner of a bed, mark it right away. Patchy symptoms often point to a drainage problem or a local soil issue, and the pattern helps the lab and your adviser narrow down the cause.
- Check plants in the afternoon and again in the morning
- Slice the lower stem to see internal browning
- Mark affected rows on a sketch map
- Keep tools clean between beds
What does a good wilt-year rotation look like?
Rotation reduces some wilts, but not all, because the survival structures last so long. Many extension guides suggest long breaks away from related hosts, with the exact length depending on the disease and crop. Ask extension for a rotation list for your crop and region, and keep grasses or cereals in the mix if recommended.
For example, if tomatoes wilted in a bed this year, plan to move that family out of it for as many years as your local guide advises and use a cover crop or non-host in the meantime.
What happens after the crop is finished?
Remove diseased plants as early as you safely can, bag them and dispose of them according to local rules. Do not compost infected debris unless your compost reaches the temperatures extension recommends, since home piles often do not. Clean stakes, cages and tools before storing them.
Stay careful with transplants too. Buy from sources that guarantee clean stock and avoid moving soil on boots and equipment between infested and clean fields.
Finish with a written note for next year that names the beds, crops and symptoms. A single page in a binder is enough, and it keeps good intentions from fading over winter.
How do watering and fertility fit the wilt calendar?
Plants under stress show wilt symptoms sooner, so a steady water supply through the season is part of the plan. Drip irrigation that keeps foliage dry and avoids pooled water at the base of plants helps reduce other diseases that can be confused with wilt, and it avoids splashing soil onto leaves and stems.
Fertility matters as well, but guesses can backfire. Take a soil test before planting, follow your state's recommendations and remember that nutrient management rules vary by state. Over-fertilizing with nitrogen can push soft growth that does not help a plant already fighting a vascular disease.
What can you plant on infested ground?
Once you have confirmed wilt in a bed, you still have options. Plant crops that are not hosts for the specific fungus, choose resistant varieties, or consider grafted plants where extension says they suit your situation. Containers with fresh potting mix and raised beds filled with clean media are another path for small growers.
Do not rely on one trick. The practical approach layers resistant varieties, clean transplants, good drainage, rotation and careful sanitation. Each step lowers the odds a little, and together they keep the crop productive in spite of the fungus.
Sources and further reading
Last reviewed: November 2026. Educational information, ranges only. Confirm timing with your county extension office.