Squash leaves, cucumber leaves drying out
Question from Laurie:
I heard you speak at the Bernardo Gardeners club this afternoon and wanted to tell you how much I enjoyed your presentation. I’m not a member, but a friend of mine invited me to come. My question to you is this: What would make our cucumber and squash leaves shrivel and dry up? They started out beautifully green and healthy and as a matter of fact, a squash is growing in our compost pile and its leaves are a luscious deep green. Are the ones with dry leaves in the garden needing more nitrogen in the soil?
Answer from Pat:
Thanks so much for your comment on my talk today. Glad you enjoyed it! Squash and cucumbers are both cucurbits and thus are subject to many of the same diseases and pests. Probably the most common cause of squash leaves shriveling and drying up is from powdery mildew. This disease is caused by weather that is cool and overcast or foggy but can also happen in dry weather. One plant infects another with fungal strands like hairs and spores that travel on the air from plant to plant. When mildew hits the leaves they go white and wilt, dry, and shrivel, sometimes dying. Severe infection can even kill some plants. Others may continue bearing since new leaves continually grow but the plant will not be as productive. Also the appearance of the plant is not pleasant. The best answer to the problem is to always choose and plant disease-resistant varieties, especially mildew-resistant varieties. See the video on mildew I made on this website and it will explain what to do. Serenade™ is an organic biological spray that will control the problem as also will a spray that coats the plant like a Christmas-tree spray creating a barrier against pest and diseases. (Moisture-In-5™ is one kind Cloud Cover™ is another.)
A second possible reason for squash and cucumber leaves drying up and shriveling is nematodes, but I have found most healthy plants to be largely resistant to nematodes. They can usually carry on despite the nematodes. See my video on nematodes for explanation of soil solarization and also planting nematode attracting marigolds. Adding beneficial nematodes to the soil can help cut down on nematode damage, but the best solution is building up the organic content of the soil and growing strong pest and disease-resistant hybrids and keeping the soil moist. Good home-made compost helps kill nematodes since it often contains beneficial ones.
Another problem can be bacterial wilt of cucumbers. This can best be controlled by controlling cucumber beetles and some other pests that attack squash plants. Pests can build up in the soil just like diseases so always rotate plants. Use a layer of earthworm castings over the roots to help the plants to fight off pests. Also try spraying the plants with a barrier such as Moisture-In-5™that I demonstrated on the video on controlling mildew. A film covering the leaves will prevent pest damage and also diseases. The white mildew disappears immediately when you spray the leaves.
Crop rotation helps to fight off both pests and diseases that build up in the soil. Grow crops year round, and always amend the soil with fresh organic compost before planting as well as adequate fertilizer. Hand pick pests, use yellow sticky traps as well as earthworm castings, but best of all grow the superior disease-resistant plants from seeds, not the plants you buy in the nursery that are from cheap seeds and often sick already before you buy them. Seeds of cucumbers and squash are super easy to grow from seeds. Why bother growing them from plants, though if I can find a good cucumber in the nursery I’ve sometimes grown them from transplants but they weren’t as good. Squash—well it’s just plain ridiculous to buy the plants. Same for melons.
The reason your squash vine in the compost pile is not sick is because the soil is so healthy full of beneficial fungi and beneficial nematodes that are killing all the bad things!