Zucchini yellow mosaic typically causes the leave lobes to become long and narrow. All three viruses are found in wild and volunteer cucurbits. Watermelon mosaic virus also occurs in weeds such as goosefoot, lambsquarters, Russian thistle, various legumes, cheeseweed and other related plants. All three viruses are transmitted by many species of aphids. In general, spread of potyviruses in the field occurs when aphid activity is high and is often very rapid and localized.
Mosaic viruses are difficult to control.
Spraying with insecticides is rarely effective for control because the insect transmits the virus before being killed by the insecticide. Silver reflective plastic mulches applied at planting have been shown to be effective in repelling aphids from plants, thereby reducing or delaying virus infection. These mulches help plants off to a healthy start and are effective until expanding foliage covers the reflective surface. Reflective mulches may need to be removed in the desert areas when summer temperatures are excessive for optimal growth of plants. The Regents of the University of California.