Bacterial Wilt
Act nowBacterial disease · spreads to other plants
Bacterial wilt is spread by cucumber beetles feeding on the plant, and there is no treatment once it is inside. The stem test is genuinely definitive and takes ten seconds, and it is the fastest way to distinguish this from the other causes of a suddenly collapsed cucurbit.
What it looks like
Individual leaves wilt suddenly and dramatically while still fully green, then whole runners, then the plant. No yellowing, no spots — just collapse. Cut the stem, touch the two cut faces together and pull them slowly apart: sticky white threads stretch between them.
How to confirm it
- The string test: cut stem, press the faces together, pull apart. Sticky threads confirm it.
- Wilting without any yellowing — the leaves are still green when they collapse.
- Often starts with one leaf or one runner and takes the rest over days.
- Cucumber beetles present or recently present.
What to do
- 1Remove and bin the plant immediately. It is a reservoir for the beetles to spread from.
- 2Control cucumber beetles on remaining plants.
- 3There is no cure and no spray that helps.
What it gets confused with
One observation settles each of these.
Look at the stem base for a hole and orange frass. Borers leave physical evidence; bacterial wilt leaves sticky threads.
Fusarium yellows leaves before wilting and shows brown staining in the stem. Bacterial wilt collapses green leaves and strings.
Preventing it next time
- Row cover from planting until flowering to exclude cucumber beetles.
- Grow resistant varieties where available; butternut squash is largely unaffected.
Plants affected
Check these two things first
- Push a finger into the soil, two knuckles deep. Wet soil plus a wilting plant means too much water, not too little — and it is the commonest reason a plant is dying. Dry soil plus crisp leaves means the opposite. The leaves look nearly identical either way, so the soil is what tells you.
- Turn a damaged leaf over. Half of all diagnoses live on the underside: fuzz means downy mildew, fine webbing means spider mites, clusters of insects mean aphids. Nothing on the top of a leaf is as informative.
Most garden problems are cosmetic and resolve without treatment. Reach for a spray last, not first.