Watermelon Mosaic

Do you see spirals on your watermelons? 

Watermelon mosaic (WMV) is a viral disease that can infect cantaloupes, squash, and other cucurbits, along with some legumes, such as peas and alfalfa, and many chenopods. Infected watermelons look like they have ringworm.

There are two different watermelon mosaic viruses: WMV1 and WMV2. While these are two distinctly different viruses, they are similar enough.

Watermelon mosaic leaf symptoms (Scot Nelson) Public Domain

Symptoms of watermelon mosaic

Symptoms of watermelon mosaic virus vary by host, but the first sign of infection is light discolorations in the leaves. This irregular chlorosis occurs along leaf edges (margins) and veins. Leaves may also be small, deformed, blistered, or wrinkled. That wrinkling is called rugosity. Finally, infected fruit develops a mottled appearance. The mottling looks like light-colored rings just under the skin. Warty growths may also appear, and fruit production is minimal.

How to prevent watermelon mosaic

Spread predominantly by aphids and occasionally leaf miners, watermelon mosaic virus can also travel on garden tools and clothing, so sanitize your tools regularly. The virus survives inside aphids for only a few hours, so physical barriers between potential carriers can also reduce infection. Crop rotation and removing infected plants can break this disease triangle. ​Horticultural oil spray can also interrupt transmission of this virus but may cause problems of its own.

Weeds, such as lambsquarters, cheeseweed, goosefoot, and Russian thistle, can act as vectors , can act as vectors for this disease, so keep them away from your watermelon and other susceptible plants.

Insecticides are ineffective against watermelon mosaic because the disease is transmitted before the chemicals kill the carrier. You can use reflective mulches under susceptible plants to repel aphids. If you use reflective mulch, remove it before the summer sun uses it to cook your plants.