Viruses Affecting Cucumber Plants

Mosaics

• Cucumber mosaic virus, commonly called CMV, is mainly transmitted by aphids, but may also lurk in some seeds. Symptoms appear first on young leaves, which develop small yellowish areas and may appear crinkled. As the leaves grow, they turn mottled, and the entire plant suffers stunted growth, producing less fruit than expected. The cucumbers that do develop have yellowish-green mottled leaves with dark green near the stem. The fruit may appear warty and blunt.

  Watermelon mosaic virus causes green mottling with dark green on the leaves and knobby or distorted, short fruit. Squash mosaic virus, transmitted by cucumber beetles or via infected seeds, causes light and dark green mosaic patterns on both leaves and fruit. The plant's growth may be stunted and the fruit becomes deformed and warty.

  Use certified virus-free seeds and control aphids and cucumber beetles until the growing season ends. Try planting corn on the windward side of the cucumber garden to help screen out insects. Pull up and destroy infected cucumber plants to keep the virus from spreading. Wash your hands and disinfect gardening tools between uses and between plants to avoid transmitting the virus to healthy plants.

Tobacco Ringspot Virus

• Tobacco ringspot virus (TRSV) is mainly transmitted by the American dagger nematode (Xiphinema americanun). Infected plants have stunted growth and an obvious mosaic pattern during the early stages of the disease. Later growth appears small and dark green. The virus progresses from the roots upward. Use only certified TRSV-free seeds or resistant varieties of seedlings. As with mosaic viruses, disinfect all gardening tools and wash your hands with soap and water to prevent the spread of this virus. Remove and destroy infected plants.

Cucurbit Yellow Stunting Disorder

• Cucurbit yellow stunting disorder virus first appears in mature growth and looks like water stress, with yellowing between the leaves' veins. Older leaves curl up and may fall off the plant as it struggles to recover, and fruit comes in smaller than normal. No suitable chemical or biological controls are available. Cucurbit yellow stunting disorder is transmitted by whiteflies (Bemisia tabaci biotypes) and by plant-to-plant infection. Use high-quality seeds certified free of cucurbit yellow stunting disorder virus, and employ pesticides to control whiteflies.

Preventing Disease

• In addition to planting virus-free seeds or disease-resistant cucumber varieties and meticulously sanitizing all gardening equipment, change where you plant. Don't plant cucumbers in or next to the same area next year that you grew them in this year. Avoid planting cucumbers near brushy or weedy areas.

  Wait until the soil reaches and sustains at least 65 degrees F before planting. To avoid standing water that can breed disease, choose a planting site that has good drainage. Dig up weeds and volunteer cucumber plants and take them away before destroying them. Do not compost infected cucumber plants. Begin a pesticide program as soon as the seedlings appear, and use fungicides when necessary. Follow product directions for all pesticides and fungicides.