Cucurbit viruses—Potyviruses, Mosaic viruses, Cucumber aphidborne yellows, and Lettuce infectious yellows
Symptoms of virus diseases include mottling of light green, yellow, or white areas on leaves, clearing of veins, thickening of leaves, and reduction in growth and yield. Fruit may be deformed.
Most viruses attacking cucurbits have a wide host range, which includes carrot, lettuce, tomato, beans, peppers, and several weed species. Transmission to cucurbits from other host plants requires contact with plant sap. The most common means of spread is through feeding by insects that have fed on the sap of infected plants. Usually only one or a few species of insects transmit a specific virus. Many species of aphids transmit potyviruses and cucumber mosaic virus. Cucumber aphidborne yellows is transmitted by the cotton aphid and the green peach aphid. The spotted cucumber beetle and other related beetles vector squash mosaic virus, and the sweet potato whitefly transmits lettuce infectious yellows.
Viruses are transmitted by insects, such as aphids, whiteflies, and cucumber beetles. Remove infected plants as soon as they are detected. It is not practical to try to control virus diseases by using insecticides to control insects. Using reflective mulches may reduce or delay infections as it helps repel insects from plants. Covering young plants with row cover can also protect them from insects.
Watermelon mosaic virus on squash
Mottling caused by watermelon mosaic