Why Does My Zucchini Look Unhealthy?

Are the leaves covered with white powder?

Do the leaves have pale areas on upper surfaces and "downy" patches underneath?

Are the flowers covered with gray mold, leaves may be blotched or discolored?

Do the leaves have yellow patches, the older leaves may be mottled and distorted?

Are the leaves curled and yellow?

Are the vines suddenly wilting, small entry holes in the stem are apparent?

Do the leaves have chewed holes in them?

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

Are the leaves yellow and the plant looks weakened?

Are the leaves stippled with yellow and the foliage is webbed?

Are the seedlings clipped off at the soil line?

White, powdery patches on the leaves are caused by a fungal disease Powdery mildew. Powdery mildew usually appears in damp places. Encourage good air circulation around the affected plants by thining them and any surrounding plants. Water plants from bellow to keep foliage dry. Any affected leaves should be cut off and removed.

Pale areas on upper surfaces of the leaves and "downy" patches underneath are caused by Downy mildew. This fungus spreads quickly during cool, wet nights and warm, humid days. Leaves will wilt and die. Remove and destroy all affected plant parts and encourage good air circulation around plants by thining them. Water plants early in the morning to make sure they dry before nightfall.

Gray mold on flowers is probably caused by fungal disease - Botrytis blight. You can only prevent Botrytis blight disease by planting flowers in areas with good air circulation. Water plants sparsely. Severely infected plants should be removed. Spray weekly with a copper fungicide until the disease is under control.

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.

Distorted, curled leaves are caused by aphids. These tiny insects cluster under leaves and on growing tips where they feed on plant sap. Leaves, stems, and buds get distorted, and later leaves and flowers drop from the plant. You can control them by washing them off the plant with water spray. Insecticidal soap should be used with severe infestations.

Probable cause for this 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.

Leaves with chewed holes 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.

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.

Yellow leaves and stunted look are caused by whiteflies. These tiny, mothlike flies and their larvae feed by sucking plant juices. Whiteflies secrete honeydew, a sugary substance that makes leaves sticky to the touch. Control whiteflies by eliminating garden weeds and by introducing green lacewings in the garden. Spray infested plants with insecticidal soap every 3 days for 2 weeks.

Leaves stippled with yellow and webbed foliage is caused by spider mites. These tiny, spider-like pests feed by sucking sap from the underside of the plants leaves causing yellow flecking on the upper leaf surfaces. You can control spider mites by spraying plants thoroughly with water 2-3 times a day for several days. For severe infestations, spray plants with insecticidal soap, or pyrethrin as a last resort.

If the seedlings of your plants are cut off at the soil level, most likely cause are cutworms. They feed at night by cutting off young plants and sometimes eating them whole. During the day, they are hidden below the soil surface. Control them by introducing parasitic nematodes to the ground. Using BTK spray on the ground will also control their numbers.

If the whole plant suddenly droops, from the bottom to the top, turning yellow, the most likely cause is a disease - Bacterial wilt. Destroy infected plants immediately. Prevent problems by controlling beetles, since they spread the disease.