The Q&A Archives: Odd-shaped Leaves on Squash

Question: My bananna squash plants are growing and seem to be healthy except that the newest leaves are small and more tightly closed in a funnel shape, as opposed to the older leaves which are large, open, and normally shaped. The leaves are turgid, not limp, and are not being attacked by squash bugs or other obvious pests. The plants receive plenty of water, and I've fertilized them at regular intervals. The fruits are setting and seem to be normal and healthy. I've also noticed one of my crenshaw melon plants exhibiting this same behavior. What could be wrong? I've noticed this same phenomenon in years past.

Answer: Without seeing the problem, I'd suspect that your squash plants have a virus. Viruses are small transmissible pathogens that use components of their host plant cells to multiply. In the process of infecting their host, they often damage or disrupt the plant's normal growing pattern, causing such visible symptoms as leaf mottle, leaf distortion, plant stunting and flower color break. Less visible problems caused by virus infection may include slower growth of plants, inefficient use of nutrients and less tolerance to other stresses, leading to overall failure to thrive.

Viruses may be spread vegetatively (in corms, bulbs or cuttings), mechanically (on tools or through movement of equipment, people and animals), by insect vectors (thrips, aphids or whitefly), aerially by pollen, in soil by fungi, or by parasitic nematodes.

The potential for disease to spread from weeds, through the growing season, is serious. It is important that weeds are controlled since they may harbor the virus as well as the aphid vectors.

Viruses cause mosaic patterns (light green, dark green) in leaves, puckering, leaf distortion, stunting, shortened internodes and misshapened fruit. Cucurbit viruses generally overwinter in weed hosts. Avoid late season planting and control weeds around gardens.

You may want to take a sample of the problem to your local Cooperative Extension for positive identification. Contact Utah State University Cooperative Extension at the Courthouse in Fillmore. Phone (801) 743-5412.

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