Pepper mild mottle virus

Pepper mild mottle virus (PMMV) is a plant pathogenic virus that belongs to the plant virus genus, Tobamovirus (The tobacco mosaic virus family). Like other viruses in this genus, it has rod-shaded particles (312 x 18 nm) and is easily transmitted by mechanical inoculation. It can also be transmitted by contaminated seeds. No insect vector is known.

Most cultivars and species of pepper (genus Capsicum) are susceptible to PMMoV. However, this virus does not affect tomato, aubergine or tobacco, which are in the same family (Solanaceae).

Symptoms
Symptoms vary depending on host, but may include:

Basil
Symptoms of infection of basil currently unavailable.

Chilli & Sweet pepper
Symptoms caused by PMMoV on pepper plants may vary between cultivars. Infected leaves are frequently puckered and mottled yellow or light green. Leaf symptoms are more evident on younger leaves. Plants can be stunted, especially when the infection occurs early in the plants development. Although infected fruit can be reduced in size and show variations in color (mottling and color changes at maturity), the most obvious symptom is the distorted or lumpy appearance of the fruit. Older fruit may develop brown streaks or splotches.

Seed
Infected seed can be treated with heat, acid, or trisodium phosphate, but virus both on the seed surface and inside the seed must be removed to ensure freedom from disease. Seed treatments can reduce the seed germination percentage even if done accurately. Although the gene for resistance has been identified, there are very few resistant field cultivars available.

Plant
There are no chemical or biological control methods that can be used to control the disease once the plant is infected.

Prevention
Avoidance is the best means of control. Like other members of this family of viruses, the virus is very stable and can be present on skin, clothing, tools and equipment so infected plants should be handled as little as possible and infected fields should be worked (staked, tied, harvested, sprayed, etc.) last to avoid spreading the virus to uninfected areas. Infected plants should only be removed if elimination can be done without contact with healthy plants. A symptomless plant on either side of those removed should also be rogued, as it is likely that they are also infected. Some viruses can be spread through smoke so diseased plants should be disposed of by composting or burying them away from fields where peppers will be grown rather than by burning them.

To reduce spread of the disease, anyone working with the plants should wash their hands with 70% alcohol or strong soap, also cleaning under the nails. Clothing should be washed as frequently as possible. Equipment should be washed and then cleaned with 3% trisodium phosphate and not rinsed. Stakes from infected areas of the field should be discarded or soaked in 3% trisodium phosphate before being reused. Household bleach can also be used to clean equipment or stakes.