Squash are one of the most popular of vegetables. To fully enjoy the rich taste of squash regardless of the season, pick the summer varieties while the rind and seeds are still immature but leave their cooler weather cousins on the vines until they fully mature.
Like most vegetables, squash thrive in loose soil brimming with organic matter. They like a lot of water but keeping their leaves dry is a best practice to prevent disease. Unfortunately, squash leaves and vines are susceptible to a myriad of insects and diseases.
Common Leaf Problems and Least-Toxic Controls
Chewed Holes may mean that Cucumber Beetles are present and as they may spread bacterial wilt and other viruses, they must be controlled immediately. Pyrethrin dust or spray are effective controls as is planting beetle resistant varieties such as "Blue Hubbard" and "Seneca."
Leaves with yellow patches and mottled and distorted older leaves probably signals an infestation of one of several mosaic viruses. Remove and destroy the plants and control any beetles or aphids that may be present on the remaining plants or on the soil. Plant virus-tolerant varieties such as "Multipik" or "Napolini" in the next garden.
Curled, yellow and wilted leaves are an indication of an aphid infestation. Blast them from the plants with a strong stream of water or spray them with a weak solution of insecticidal soap. Place foil mulch around plants or plant silver-leaved cultivars like "Cocozelle."
Spotted, blotched or brown leaves indicate that one of several fungal or bacterial diseases are active. Reduce problems by watering only the soil and keeping the foliage dry. Spray infected plants with a dilute copper spray. Plant "Super Select" and "Zucchini Select" or other resistant varieties in future gardens.
If vines wilt suddenly, squash borers may be infesting the stems. They advertise their presence with masses of yellow-green sawdust excrement so stems can be slit with a knife above the excrement and the larvae located and destroyed. Cut stems may be re-rooted in moist soil and plants injected with parasitic nematodes to prevent future outbreaks. "Sweet Mama Hybrid" is resistant to vine borers.
As always, local knowledge of garden pests and their control is best, so ask your gardening neighbors, your county extension agent or local garden center what the least-toxic options are for your garden.