Phytophthora Blight
Plants in the low wet part of a bed collapse in a group after heavy rain, with a dry brown corky girdle at the stem base on peppers and a soft crown rot on squash. Fruit lying on wet soil develops a water-soaked patch that turns into a thick white sugary-looking mould, which is what separates it from ordinary root rot.
Disease checklist
Four things to look for. If most of them match what you are holding, you are in the right place.
What gets rid of it
Gentlest option first. For most backyard cases the first one is enough, so try these in order and stop as soon as it works. If you do spray something, the product label tells you how — please read the notice further down.
1Plant on raised beds or ridges
Raise the rows 8 to 10 inches so water never stands around the crowns after a storm.
raised garden bed kitTry this first2Fix the wet spots
Do not plant peppers or squash in the low corner of the garden, and open a route for surface water to leave.
3Keep fruit off wet soil
Trellis cucumbers or set squash and melons on boards or straw so the ground-facing skin stays dry.
straw mulch for garden beds4Remove infected plants and fruit at once
Take collapsed plants and rotted fruit out of the field before they sporulate, and do not compost them.
5Do not move soil and water between beds
Clean tools and boots, and never irrigate from a pond that has drained an infected bed.
boot brush scraper outdoor6Long rotation to non-hosts
Follow with corn or a grass cover for several years, since peppers, cucurbits, tomato and beans all feed the same pathogen.
cereal rye cover crop seed
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Which plants get phytophthora blight
Every plant we cover that gets phytophthora blight, grouped by type — tap any one to open its page. A note beside a plant came from that plant’s own entry, because the same disease can be a minor nuisance on one plant and a serious problem on another. Plenty of plants we do not cover get it too.
Plant families hit hardest
Related plants often share the same problems, so if one plant in a family has it, check the others. The largest group here is Cucurbitaceae, with 4 of the 7 affected plants.
- Cucurbitaceae4 plants
- Solanaceae3 plants
When to treat
Act on drainage before you plant, because the resting spores survive in soil for many years and once a plant has a girdled stem or a rotted crown nothing will bring it back.
Timing only — the label is the law
This page tells you when to watch for phytophthora blight and when treating is worth considering. It is not a recommendation to apply any particular product. Read and follow the product label before you spray — under federal law the label is the legal instruction, and using a pesticide against it is illegal.
- Check the pre-harvest interval. Every product that’s cleared for an edible crop sets a minimum number of days between spraying and picking. Find it on the label before you spray anything you intend to eat.
- Check the re-entry interval before you or anyone else works in the treated area again, and use the protective equipment the label names.
- Confirm the product is registered for your crop in your state. This page groups many different crops together, and a product legal on one of them is not legal on all of them — state registrations differ too. Your state pesticide agency or local extension office can confirm both.
- Rates and mixing instructions come from the label, never from us. We don’t publish them because they differ by product and formulation.
Other problems on the same plants
If a plant gets phytophthora blight, these are the problems it most often gets as well, so they are worth checking for while you are out there. They tend to appear together; one does not cause another.