Zucchini Yellow Mosaic

Warty zucchinis with skinny leaves may mean the zucchini yellow mosaic virus has infected your plants.

Fruit distorted by zucchini yellow mosaic (Rasbak) CC BY-SA 3.0

​No garden would be complete without the versatile, fast-growing zucchini. A favorite in stir-fry, bread, and the ever-popular chocolate zucchini cake, zucchini can be a very productive plant, but only as long as it stays healthy.

Zucchini yellow mosaic symptoms

Whitened leaf veins, mottled, abnormally small leaves with alternating light and dark areas, and deformed, warty fruit are all signs of zucchini yellow mosaic. These are also symptoms of watermelon mosaic and papaya ringspot. These two viral diseases often occur in tandem with zucchini yellow mosaic. Watermelon mosaic infections exhibit blistered leaves, while zucchini yellow mosaic has long, narrow leaf lobes, creating a shoestring or ferny appearance.

Zucchini yellow mosaic on squash leaf (Public Domain)

Zucchini yellow mosaic host plants

In addition to infecting zucchini, zucchini yellow mosaic also infects other cucurbits, including cantaloupe, cucumbers, melons, pumpkins, squash, watermelon, and some gourds. Aphids bring this disease to your garden.

Zucchini yellow mosaic management

Controlling aphids is difficult. These pests seem to appear overnight in huge numbers. And all it takes is one aphid to get the whole process started. Unfortunately, insecticides are rarely effective at managing zucchini yellow mosaic because the disease has often been transmitted before you even know the aphids are there. Reflective mulches can discourage aphids. Remove or cover the reflective material before it gets too hot, or your plants will cook where they stand. Row covers can reduce access to susceptible plants.

This disease can also travel on infected garden tools and seeds, so sanitize your garden tools regularly and get your seeds from a reputable source (and not that zucchini from the grocery store). Remove infected plants and replace them with resistant cultivars.

Since this virus is only viable for a few hours within their aphid carriers, creating a physical barrier of tall, non-host plants around your cucurbits can be enough to prevent the aphids from getting to the plants while the virus is still active.