Although severity of symptoms may vary with the type of pepper plant, a first sign of infection is the mild puckering or wrinkling of the leaves. Older leaves display a mottled yellow appearance or turn a lighter shade of green. In the veinal form of the virus, yellow lines appear along the main veins of the leaves, followed by bleached out banding on outer veins. If the seed itself is infected, stunted growth is common. The fruits are usually small, misshapen and have a lumpy appearance.
The virus enters the pepper plant through tiny abrasions found on the stem or leaves. The pepper mild mottled virus (PMMoV) can be spread mechanically by touch or by infected soil, tools or seeds. Its cousin, the pepper veinal mottled virus (PVMV), which exhibits similar symptoms in infected plants, is spread primarily by winged aphids. The aphids feed on certain weeds like jimson and black nightshade--which can carry the virus--then bite and infect nearby pepper plants.
Experts recommend that avoidance of the virus is the best form of control because there are few pepper plants resistant to the virus. If you suspect an infected plant, remove it and all other plants adjacent to it. Clear away any infected plant material in the soil. Wash hands and clean nails with an alcohol gel before touching healthy plants or their surrounding soil. Disinfect trowels, shovels and other tools with household bleach.
Prevention and Solution
The PMMoV form of the virus exists in the soil and often the seed itself and is impossible to reverse once infected. For this reason, rotate pepper plants to a different area of your garden each year. To prevent the PVMV form, which is spread by insects, plant peppers away from plants that attract aphids, such as tomatoes and melons. Removing nearby weeds that could carry the virus also reduces risk of infection.
To help confirm if your pepper plants are infected with pepper mottled virus, contact your local agricultural cooperative extension to have them tested. Their lab can identify the virus by performing a simple test.