Bacterial wilt

Erwinia tracheiphila

A bacterial wilt of cucumbers and their kin, carried by cucumber beetles: leaves flag and the whole plant collapses, with a telltale white string of ooze in the cut stem.

Bacterium No cure Spread by insectsSpread by contact Spreads to neighbors

What you'll see

Leaves flag and wilt, at first only in the heat of the day, then for good, and the whole plant collapses.
Cut a wilted stem across, press the two ends together and draw them apart — a fine white string of sticky ooze bridges the gap, which confirms it.
Wilting begins on individual leaves near a beetle feeding scar, then runs through the plant.
The stem stays firm and green at first even as the foliage dies, unlike a soft rot.

Why it happens

A bacterium that clogs the water-conducting vessels of the plant. It cannot survive long on its own and is carried from plant to plant in the gut of cucumber beetles, entering through the feeding wounds they make.

It appears once cucumber beetles are active in warm weather; cucumbers and melons are most susceptible, and a heavy beetle year means a bad wilt year.

Treating it

There is no cure; pull and destroy a wilting plant promptly so it cannot feed more beetles.
Confirm it first with the sap-string test before condemning the plant.
Control the cucumber beetles to protect the plants still standing.
Do not compost infected plants.

Keeping it away

Keep cucumber beetles off young plants with fleece or fine mesh, lifting it only for pollination.
Grow resistant cucumber and melon varieties where the wilt is a regular problem.
Check plants often and squash or trap beetles early in the season.
Clear crop debris and rotate cucurbits to keep beetle numbers down.
Protect vulnerable seedlings, the stage at which infection does most harm.

Who gets it

The cucumber family — cucumbers and melons most of all, with squashes, courgettes, gourds and pumpkins less often affected.