Dwarf Mosaic Virus

The symptoms of this disease of corn vary with variety and stage of growth, but usually start with chlorotic spots and flecks. These gradually elongate into chlorotic streaks that form the characteristic mottled mosaic pattern which gives the disease its name. There may also be yellowing of the whole leaf and sometimes streaks of red. The plants are commonly stunted because the internodes between leaves are shortened (hence the name Dwarf Mosaic).

Dwarf Mosaic is commonly transmitted by aphids. They acquire the virus by feeding on an infected plant for a few minutes and can transmit it to other plants for a further 15-30 minutes. If the disease is prevalent in your area you might want to use row covers to keep them off of your plants. Early planting can also help as the plants will be past their most vulnerable stage before the aphid population builds up.

Mosaic is sometimes introduced into the garden on vegetable seedlings, so it’s best to grow your own, using disease-free seeds. Corn is so easy to grow from seed that there is absolutely no point in buying corn seedlings anyway.

If any plants start to exhibit symptoms of mosaic remove them immediately to reduce source of infection. Viruses are frequently spread by gardeners, so don’t touch wet plants and wash your hands frequently with soap and water (especially after touching infected plants).

You can minimize the effect of viruses by keeping the plants in good health with lots of nutrients and water. Some resistant cultivars are available.

Image: Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org