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Bacterial wilt of cucurbits: how to recognise and treat it

Disease

Bacterial wilt of cucurbits — Photo: Eeshie, CC BY-SA 3.0, Wikimedia Commons

Symptoms

Leaves on one runner turn dull green and wilt, even in moist soil; the wilt spreads along the vine to the crown and the whole plant dies.
Wilted leaves develop yellow and dead patches and shrivel.
Cut a wilted stem and slowly pull the two ends apart — sticky threads of bacterial ooze stretch between them; in a glass of water a cloudy stream flows from the cut end. The test works best on cucumber and melon.

Organic treatment

Remove infected plants at once and burn (where allowed) or bury them; do not compost — they attract more cucumber beetles.
Cover young plants with row covers on hoops until flowering to keep striped and spotted cucumber beetles off, then remove them for pollination.
Spray kaolin clay on seedlings or transplants before beetles arrive; it repels them but does not kill them.

Chemical treatment

No spray cures infected plants. To protect healthy ones, control cucumber beetles with pyrethrins or azadirachtin labelled for them, sprayed in the evening; follow the label.

Reference information, not a guarantee. Read and follow the label of any product: dose, safety and the days to wait before harvest.

Prevention

Scout seedlings at least twice a week; on cucumber, melon and zucchini act before beetles exceed 1 per 2 plants.
Protect plants most carefully until the 5-leaf stage, when infection does the most harm.
No resistant varieties are available; watermelon and less susceptible crops such as most pumpkins suffer much less.

Plants it affects

Sources

Figures checked against these sources.