Cucumbers (Cucumis sativus), like all cucurbits, produce large leaves and thick vines. The plants are well equipped for producing their juicy, flavorful fruit. Sometimes, however, the leaves wilt due to disease, insect infestation or even environmental conditions. Whatever the cause, healthy plants are better able to survive wilting. Plant cucumbers in full sun, in well-draining soil and water them frequently.
Cucumbers sometimes wilt during periods of high heat, especially when the heat is accompanied by drying winds. In these conditions, the leaves lose water more quickly than the roots can take up moisture from the soil. Plants can spring back from one or two episodes of heat stress, but continuous wilting can cause reduced yields or poor quality fruit, stunted growth and even plant death. To prevent wilting from heat stress, water more frequently. This is one time when using overhead sprinklers is appropriate and even desirable. Mulch the soil with straw or untreated grass clippings to conserve moisture and install a fabric shade over the plants.
Several diseases can cause wilting leaves, and in most cases, these diseases are fatal. Verticillium wilt causes wilting, as well as light brown streaks on the interiors of the leaves and stems. Prevent it by planting disease resistant varieties and rotating crops. Sudden wilt causes wilting leaves, as well as rotting roots. It is most prevalent in heavy, soggy soils. To prevent it, add compost to improve drainage or plant cucumbers in raised beds.
Most insects that attack cucumbers leave visible damage in the forms of chewed leaves. A few, however, can cause wilting. Squash bugs, for example, tunnel through the vines, causing the leaves to wilt. Lay boards in the garden to trap and kill the adults. Look for small eggs at the base of the plants and destroy them. Aphids pierce the leaves and stems and suck out the juices, causing stippling, curled or wilted leaves. You might also notice honeydew, a sticky substance excreted by the pests, on the leaves and the ground, as well as black soot, a fungus that feeds on the honeydew. To treat aphids, spray both the tops and undersides of the leaves with a steady stream of water. Another option is to spray the leaves with an insecticidal soap. Mix 2.5 ounces of concentrate with 1 gallon of water. Apply the product on a cool, cloudy day and coat the leaves completely.
Nematodes are microscopic roundworms that cause serious damage in the vegetable garden. These pests feed on the roots of the cucumber plants so the plants can't take up moisture and nutrients from the soil. Initially, the plants' growth is stunted. Later, the plants wilt and you might notice nodules on the roots. Crop rotation helps control nematodes. In severe cases, you might have to solarize the soil, which requires spreading a clear sheet of plastic tightly over the soil for four to six weeks during the heat of summer. The high heat destroys the nematodes.
- University of Delaware Cooperative Extension: How High Heat Affects Vegetables and Other Crop Plants
- University of California Davis Vegetable Research and Information Center: Cucumber
- UC Davis Good Life Garden: Cucumber
- Clemson University Cooperative Extension: Cucumber
- Grow Organic: Safer Insecticidal Soap Concentrate
- Stockbyte/Stockbyte/Getty Images