Why Does My Squash Look Unhealthy?

Are there any small, round reddish brown spots with white to grey centers on the upper surface of the leaves?

Do the leaves have any small circular or irregularly shaped dry spots that are gray to straw in color?

Does the plant wilts suddenly, yellow streaking on the foliage is apparent?

Are the leaves covered with white powder?

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

Are the leaves curled and distorted?

Do the leaves have chewed holes in them?

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

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

These symptoms indicate Alternaria leaf spot. Warm, wet conditions favor this fungal disease. Spray infected plants with copper and/or sulfur to prevent further disease development. Plant only pathogen-free seed from a reputable nursery.

These symptoms indicate a fungal disease - Anthracnose. Keep plants dry when watering to prevent spread. Spray plants with copper when the first fruit develops if you have had problems in the past.

Bacterial wilt causes a yellow streaking on the foliage and sudden wilting. Remove and destroy infected plants. Do not replant honeydew or any other susceptible plant species in that area for several years. Control cucumber beetles because they are vectors for bacterial wilt.

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. The appropriate fungicidal spray will protect your plant from further infections.

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 and 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.

Leaves with chewed holes indicate Cucumber beetles. Beetles may be spotted, striped or banded and can be very harmful. The beetle larva can also bore through the roots of the plants. Knock off adults into a jar of soapy water and destroy them. Spade the soil to destroy dormant beetles before you plant. Use a row cover to prevent adults from feeding on young plants. In severe infestations use pyrethrin spray or dust.

Probable cause for this is Squash vine borer. 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 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 ends of the squash get soft before they are ready to harvest your squash may be suffering from Blossom end rot. This condition is due to calcium deficiency in the fruit. Prevent problems by keeping the soil evenly moist and by spraying plants with seaweed extract when the first flowers open and again when green fruit is visible.