What pests attack zucchini?

Cucumber beetles, Squash bug, Two-spotted spider mite, Whitefly

What diseases affect zucchini?

Bacterial soft rot, Bacterial wilt of cucurbits, Downy Mildew, Grey mould, Leaf Curl Virus, White mould (Sclerotinia), Verticillium wilt

Zucchini pests and diseases: how to recognise them

Q: Which zucchini problems need quick action?

Cucumber beetles: Chewed cotyledons, leaves and stems of young plants; scarred fruit rind on older plants. Bacterial soft rot: Whole roots, tubers, bulbs, heads or fruit can collapse within a few days, often leaving only the skin — in the garden and in storage. Bacterial wilt of cucurbits: 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. Downy Mildew: A white, grey or purple mould on the underside of the leaf, directly below each blotch, in damp weather. Grey mould: On strawberries, grapes and other soft fruit a soft brown rot, often as the fruit ripens; on gooseberries whole branches die. Leaf Curl Virus: Plants are stunted and stay upright and bushy because the internodes are short; plants infected young are severely stunted. White mould (Sclerotinia): Later, hard black seed-like bodies (sclerotia) 0.5–1 cm across in the mould and inside hollow stems.

Cucurbita pepo

The pests, diseases and disorders recorded for zucchini in our library, each with a photo and its first symptom. Every page has the full list of symptoms, organic and chemical treatment and prevention.

At a glance

Problems in total	12
Pests	4
Diseases	7
Growing conditions	1
Need quick action	7

How to grow zucchini · All pests and diseases

Pests

Cucumber beetlesChewed cotyledons, leaves and stems of young plants; scarred fruit rind on older plants.Also called: striped cucumber beetle, spotted cucumber beetlePhoto: Pollinator, CC BY 2.5, Wikimedia Commons
Squash bugAdults are flat, grey-brown bugs about 1.6 cm long with orange-striped abdomen edges; young nymphs are pale green, older ones grey with dark wing pads.Photo: Pollinator at English Wikipedia, CC BY 2.5, Wikimedia Commons
Two-spotted spider miteFine silk webbing over leaves and shoot tips in heavy attacks.Also called: red spider mitePhoto: Gilles San Martin from Namur, Belgium, CC BY-SA 2.0, Wikimedia Commons
WhiteflySticky honeydew on leaves, stems and fruit, followed by black sooty mould.Photo: gaucho, CC BY-SA 3.0, Wikimedia Commons

Diseases

Growing conditions

Blossom-end rotOn peppers the spots can form on the sides of the fruit near the blossom end and look like sunscald.Photo: A13ean, CC BY-SA 3.0, Wikimedia Commons

Which zucchini problems need quick action?

These spread or do lasting harm fast; check the plants and start treatment the day you see them.

Cucumber beetles: Vines suddenly wilt and die even though the soil is moist — bacterial wilt spread by the beetles; cucumbers and melons are the most susceptible, watermelon is not.
Bacterial soft rot: Potato stems may turn black and rot from the base upwards (blackleg).
Bacterial wilt of cucurbits: 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.
Downy Mildew: Badly affected leaves shrivel and turn brown or yellow and fall early; plants become stunted and some may die.
Grey mould: Small black seed-like bodies may form on the infected material.
Leaf Curl Virus: Flowers often drop without setting, so very little fruit forms — losses can be total when plants are infected early.
White mould (Sclerotinia): Roots, heads, pods and fruit can rot too, also in storage.

Plants with many of the same problems

Which plants each problem affects: sources

The links between these problems and the plant were checked against these pages.