Your plants have been affected by a virus disease, most likely squash mosaic virus or cucumber mosaic virus. This virus is transmitted to the plants by insects that have been feeding on other virus-infected squash plants, or perhaps some wild plant. Once the plant gets this disease, nothing can be done. Best preventative measures include insect control and planting varieties which will mature early in the year. This disease is more severe on late-planted squash than it is on the early spring-planted crop. The green squash (which should be yellow) is still good to eat if harvested at the proper stage of maturity. There will be little change in taste. This virus disease will eventually kill the plant.

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