How Can I Determine What Is Wrong With The Cucumbers I'm Growing?

Do the cucumber leaves have chewed holes in them?

Do the leaves have pale green patches on them, some leaves may have already wilted and blacken?

Do the leaves have yellow patches on them and are the older leaves mottled and distorted?

Are the leaves yellow, curled and wilted?

Are the leaves mottled and yellow between veins, undersides may have purple spots?

Do the leaves have spots, blotches or brown areas on them?

Do the leaves have powdery white spots, especially on upper surfaces??

Are the spots yellow and turning brown?

Are the spots water-soaked and turning gray, die and drop from plants?

Are the cucumber vines suddenly wilting?

Leaves with chewed holes in them often indicate cucumber beetles. These greenish-yellow beetles with black stripes or spots often carry viruses. Use pyrethrin spray or dust on your plants to control them. Prevent problems by planting cultivars such as ‘Lib­erty’ and ‘Wisconsin SMR58', that are tolerant of cucumber beetles.

Leaves with pale green patches that later wilt and turn black are caused by Squash bugs. Adults are brownish to black and young bugs are whitish green with dark heads and legs. They lay their bright orange eggs on the undersides of leaves. Handpick adults and eggs. Place a board on the ground near plants. Lift it each morning and destroy the bugs hiding underneath.

These symptoms often indicate viral disease - Mosaic. Afflicted plants are unproductive and fruit is bitter. Remove and destroy infected plants. Control aphids as they are the most likely carriers of the mosaic virus. Cultivars like 'Comet', ‘Fancipak', 'Liberty'. ‘Monarch', ‘Score', 'Slicemaster', ‘Striker', and 'Wisconsin SMR58' are more resistant to mosaic.

Yellow, curled and wilted leaves on cucumbers usually indicate aphids. These tiny insects vary in color, green, pink, black, gray to completely white. You can control them by washing them off the plant with water spray. Insecticidal soap or neem oil should be used only with severe infestations.

These symptoms usually indicate fungal infection - Downy mildew.

White, powdery spots on the leaves are caused by a fungal disease Powdery mildew. Powdery mildew usually appears in damp places. Encourage good air circulation around the cucumbers by thining any surrounding plants. Keep foliage dry when watering. Affected leaves and fruits should be cut off and removed.

These symptoms usually indicate a fungal disease - Anthracnose. You can control it with sulfur spray. Resistant cultivars are ‘Fancipak’, ‘Liberty’, ‘Poinsett 76’, ‘Score’, and ‘Slicemaster’.

These symptoms usually indicate one of two possible diseases - Angular leaf spot or Scab. You can control both diseases using fungicides or copper. During cool, wet weather, fungicide sprays may not be effective. ‘Fancipak’, ‘Score’, and ‘Slice master’ are resistant to scab.

Various fungal and bacterial diseases may cause leaves with spots and blotches.

The most probable cause for this condition are squash vine borers. These fat, 1 inch long larvae burrow into stems and feed on them leaving yellow-green sawdust-like excrement. Inject stems with BTK or parasitic nematodes to control them. Prevent borers by late spring BTK spray.

If vines are wilting at midday but the leaves remain green most likely cause is a disease - Bacterial wilt. Destroy infected plants immediately. Prevent problems by controlling cucumber beetles, since they spread the disease.