Sweetpotato feathery mottle

General information

Sweetpotato feathery mottle virus is the most common virus infecting sweetpotato worldwide. Sweetpotato feathery mottle virus occurs in all countries where sweetpotato is grown. The virus can reach high levels of infection in crops propagated from infected material or grown near infected crops, allowing aphid transmission from crop to crop. Sweetpotato feathery mottle virus can interact with other viruses to form Sweetpotato virus disease.

The virus causes reduced yields and a reduction in the quality of harvested roots.

Cause

Sweetpotato feathery mottle virus (Potyvirus).

Symptoms

Plants infected with Sweetpotato feathery mottle virus may not display any symptoms, or symptoms may be transient or mild. The variety, plant age and environmental conditions all influence symptom development.

When present, symptoms range from a mild mottle, yellow (chlorotic) spotting often surrounded by a purple margin or irregular chlorotic patterns vein clearing or feathering. Symptoms may be more prevalent on older leaves. Reduced plant vigour in the early establishment phase of the crop is common but not recognised until infected material is grown alongside Pathogen tested (PT) material. Storage roots elongate and become thinner over successive generations where infected plant material is used. Storage roots can display russet cracking and pale flesh colour in orange-fleshed varieties.

Severe long term infections have been reported with reduced plant vigour and considerable yield reduction.

There are three strains of Sweetpotato feathery mottle virus reported form Australia. Russet crack (RC), causing characteristic cracking symptoms on storage root skin, common (C) now called Sweetpotato virus C and Ordinary (O).

How does it spread

The virus is spread by aphids in a non-persistent manner and by using infected planting material.

Crops affected

The host range of the virus is restricted to sweetpotato and other Ipomoea species.

Control options

Use pathogen tested, clean planting material. Locate planting material nurseries or seedbeds away from established commercial plantings and use windbreaks. to reduce the risk of infection from diseased crops. Manage weeds of the Convolvulaceae family, which includes the genus Ipomoea.

Maintain good farm hygiene including around headlands, borders, native strips, roads, laneways, drainage areas, packing and machinery sheds. Once a crop has been harvested, remove all sweetpotato residues from the previous crop as soon as possible. Clean vehicles, equipment when moving between farms. Clean knives and vine cutting tools often. Regularly inspect seedbeds and commercial crops for any signs of virus infection. Discard plants with probable symptoms of virus disease.

Chemical registrations and permits
Check the Australian Pesticides and Veterinary Medicines Authority chemical database and permit database for chemicals registered or approved under permit to treat this disease on the target crop in your state or location. Always read the label and observe withholding periods.