The Q&A Archives: Why Squash Leaves Turn Whitish-Green

Question: Several of my squash plants will have their leaves start to turn whitish green. When this happens, most of the leaves of the affected plant start to turn whitish green and the growth of the plant slows down. The plant doesn't die, but it grows so slowly that it never produces any more squash. The plant never recovers. It is not a fungus growth, it appears to be discoloration of the leaf itself. The leaf is not deformed or obviously damaged. Subsequent application of water or fertilizer or insecticide doesn't make any difference. There is no sign of insects or any infestation. One plant will get it, and the one next to it won't be affected. The weather is hot and arid. The plants receive plenty of water, and plants in the sun or partial shade will get it. This happens every year, and an affected plant will never recover. What can cause this? Matthew Reed Las Vegas, NV

Answer: It sounds like your squash could be suffering from some sort of viral disease. Viruses are spread by insects such as aphids. Once a virus has set in, there is no cure, but before you pull out the plants, call your extension service (702/731-3130) and have them give you a positive ID on the problem. It could be something else. There are no squash varieties that are truly resistant, though some are less succeptible than others. Many weeds are a reservoir of the virus, so aphid and weed control are good tactics to avoid this problem in the future. Also, you can try growing the squash earlier in the season under a polyester row cover (reemay) to exclude the aphids. When the vines blossom, open the covers in the morning to invite the bees to pollinate. A final note - know your pest before spraying an insecticide. It saves you money and time, and is easier on the environment (indluding you!) if you know your foe, and can choose the appropriate weapon.

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