Zucchini is an excellent choice for the summer garden because it is so easy to grow. This nearly indestructible squash can be yellow or green and is shaped like a cucumber. It requires full sun and room to spread, as its rapidly growing vines can take over your garden plot. Despite its hardiness, the zucchini is susceptible to several viral diseases.
Squash Mosaic Virus
Squash mosaic virus is spread by the spotted and striped cucumber beetles. Seeds carry the virus, which produces chlorotic mottle (yellow spots), vein banding, and distorted leaves on seedlings. Mature plants will have symptoms including blistering, hardening and mottled spotting. Control the virus by choosing disease-free seed and controlling the cucumber beetle with sticky traps or botanical poisons such as pyrethrum or rotenone.
Zucchini Yellow Mosaic Virus
Zucchini yellow mosaic virus is a relatively new disease, first recognized in 1981. It's not known what transmits the virus, though it may overwinter in weeds. Leaf symptoms include stunted growth, mottling, yellowing, blisters and dead patches. The virus can lead to malformed, knobby and cracked fruit. Prevent the virus by keeping your garden free of weeds and buying disease-resistant seeds.
Phytophthora blight, also known as damping off, root rot, stem rot or crown rot, can occur at any stage of the zucchini's growth. Foliar symptoms include wilting, sudden seedling death, leaf spots and dark, water-soaked spots. On the zucchini, infected areas are sunken, brown and water-soaked. To avoid Phytophthora blight, plant your zucchini in well-drained soil and do not let the plants become waterlogged. Do not plant new seedlings in an area that has previously been infected, because the blight can remain in the soil for years. Fumigants such as K-pam, Vapam and Telone will suppress the disease but not eliminate it.