Common Disease Problems
Alternaria Leaf Spot: Small, round reddish brown spots, usually with a yellow halo, form on the upper surface of the leaves. Severely infected leaves turn brown, curl upward, wither and die. Fruit are not usually infected but can suffer from sunscald due to leaf loss. This disease is worse in warm, wet or very humid weather. Burpee Recommends: Avoid getting water on the foliage. Remove infected plant parts and do not work around wet plants. Provide plenty of air circulation. Contact your Cooperative Extension Service for fungicide recommendations.
Anthracnose: This is a fungus disease that attacks the fruit as it is ripening. Irregular brown spots develop on the leaves. Infected fruit develop sunken black spots that may have white mycelia during wet weather. The spots enlarge and turn black; the fruit rots. Extended periods of heat and humidity facilitate anthracnose growth. The fungus overwinters in diseased plant debris. Burpee Recommends: Provide sufficient space between plants for good air circulation, avoid overhead watering which can spread the fungus spores, keep a clean garden, remove and discard all diseased plant material and rotate crops.
Bacterial Wilt: Leaves turn brown, stems wilt and shrivel, the infected plants die. Burpee Recommends: Remove and destroy plants showing signs of the disease. Control cucumber beetles, which spread the disease. Contact your Cooperative Extension Service for recommendations.
Mosaic Virus: Young leaves are distorted and mature leaves will have an intensive mottled appearance. Fruit can have yellow spots or bumps. The disease is quite serious and be transmitted by aphids or cucumber beetles. Burpee Recommends: Remove and destroy any infected plant. The virus can overwinter in weeds so keep the garden clean. Monitor and treat for aphids and cucumber beetles. Contact your Cooperative Extensions Service for recommendations in your area.
Powdery Mildew: This fungus disease occurs on the top of the leaves in humid weather conditions. The leaves appear to have a whitish or greyish surface and may curl. Burpee Recommends: Avoid powdery mildew by providing good air circulation for the plants by good spacing and pruning. Contact your Cooperative Extension Service for fungicide recommendations.
Common Pest and Cultural Problems
Aphids: Greenish, red, black or peach colored sucking insects can spread disease as they feed on the undersides of leaves. They leave a sticky residue on foliage that attracts ants. Burpee Recommends: Introduce or attract natural predators into your garden such as lady beetles and wasps who feed on aphids. You can also wash them off with a strong spray, or use an insecticidal soap.
Blossom End Rot: Ends of the squash gets soft before they are ready to harvest. This can occur when there is not enough calcium in the soil or when root damage and water stress reduce the uptake and movement of calcium through a plant. Burpee Recommends: To avoid BER, properly site and prepare your garden bed before planting. Most crops need full sun and loose, well-drained organic soil. Test your soil to see if calcium is recommended. If it is, apply lime in the recommended quantity according to manufacturer's instructions. Avoid planting too early in cool soils as this can inhibit early root development, making the plant more susceptible to BER. Avoid wide fluctuations in soil moisture by applying 2-3 inches of mulch. This will moderate the release of water to plant roots, and also keep the soil from drying out when it is directly exposed to the sun.
Cucumber Beetles: Beetles may be spotted, striped or banded and can be very harmful. Beetles are usually ¼ to ½ inch in size. Beetles start feeding as soon as they hatch and can kill or slow the growth of the plants. Beetle larva can also bore through the roots of the plants. Beetles can also transmit diseases from plant to plant. Burpee Recommends: 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. Consult your Cooperative Extension Service for other insecticide recommendations.
Spider mites: These tiny spider-like pests are about the size of a grain of pepper. They may be red, black, brown or yellow. They suck on the plant juices removing chlorophyll and injecting toxins which cause white dots on the foliage. There is often webbing visible on the plant. They cause the foliage to turn yellow and become dry and stippled. They multiply quickly and thrive in dry conditions. Burpee Recommends: Spider mites may be controlled with a forceful spray every other day. Try hot pepper wax or insecticidal soap. Check with your Cooperative Extension Service for miticide recommendations.
Squash Vine Borer: The brown headed larva will bore into stems, feed through the center of the stems, block the flow of water and the plants will collapse and die. The first sign of this pest is that the plant will wilt during the day and perk up at night. Check the base of the plant for holes and you will see what looks like sawdust. Burpee Recommends: Pull and destroy any plants killed by squash vine borers. Row covers will prevent the female from laying her eggs. In most areas there is only one generation each year so a second crop can be planted in early July. Although you can’t always save the plant, as soon as you see the wilting plant, cut a slit in the stem above the hole using a sharp knife. Kill the borer with the tip of the knife, or pull it out. Mound soil over the cut area and keep the soil moist. New roots may grow and the plant may live. Rotate crops. Consult your Cooperative Extension Service for insecticide recommendations.
Summer Squash FAQs
Why does my plant have only male flowers? Male flowers open two weeks before female flowers open. If plants are stressed (too hot, too cold, too crowded, too wet, too dry, or infested) they will abort female flowers almost immediately.
Why do my plants have flowers but no fruit? If flower stems are thin and straight, they are male flowers; if flower stems are round and swollen like a baby fruit, they are female flowers.
You need both to make fruit. Male flowers will open before female flowers.
Can I eat summer squash raw? Yes pick the fruit when tiny and slice for salads.
Why do my tiny fruit turn brown and fall off? This is usually the result of poor pollination. Squash needs bees to pollinate its flowers. Be sure you have plenty of bees to ensure good pollination. You can try hand pollinating too.
What are good companion plants for my squash? Peas and beans are good choices because they fix nitrogen into the soil. Radishes can help deter cucumber beetles.
Winter Squash FAQs
Why is my spaghetti squash green and not yellow? This squash starts green and ripens to yellow.
If my squash are next to my pumpkins, will I get mixed (hybrid) fruit? No, it will not affect the fruit; however, you cannot save the seeds as this will be a mixed type of fruit.
How long will winter squash store? After being properly cured winter squash can be stored for several months.