Fresh fruits and vegetables are two of the perks of having your own garden in the summer. Besides the usual work of planting, weeding, fertilizing and watering, keep a lookout for pests and diseases. Identifying the specific disease of a plant is the first step to controlling the disease. If you suspect your summer squash is the victim of a disease, do not eat it. According to North Dakota State University, practicing crop rotation and proper crop removal in the fall can help prevent future diseases.
Examine the color of the squash. Is it mottled and colored a splotchy green and yellow, as opposed to a solid color? Are the leaves of the plant puckered and smaller than normal? Run your hands along the squash to check the texture. It may have knots and be misshapen. If your squash has these symptoms, it has a disease called the squash mosaic virus. Mosaic diseases are often carried by cucumber beetles and aphids.
Check the leaves of the squash plant for a powdery-type of white spot. This is called powdery mildew, a fungal infection. It often spreads rapidly during dry and hot weather. In severe cases, the leaves may turn yellow.
Look for light brown spots on the plant's older leaves. They may appear wet and are typically circular. According to North Dakota State University, this disease is called Alternaria blight, or simply blight. When this disease affects the squash itself, the squash develops sunken spots that may have dark mold.
Examine the squash for signs of wet rot. This disease is caused by the Choanephora fungus. It appear to be a white mold. According to Alabama A&M and Auburn Universities, it typically begins in the squash plant's blossoms, then spreads to the stem and squash. Affected squash have numerous points of white fungus that turn to black rot after a couple days.