Cause The pea seedborne mosaic virus spreads through infected seed. This virus was not known to be in the Pacific Northwest until 1968 and has not escaped into other crop or weed hosts in the United States. The pea aphid (Acyrthosiphon pisum), the green peach aphid (Myzus persicae), and the potato aphid (Macrosiphum euphorbiae) are efficient vectors. Although aphids do not retain the virus for long periods, natural spread over a distance of 400 meters has been observed. At normal aphid population levels, infection incidence can increase significantly during a single season of seed-crop increase. In extreme cases, all seeds of infected seed lots contain seedborne virus.
Symptoms The plant is slightly stunted and upper leaves are slightly rosetted and roll down sharply. Depending on the variety, rolled leaves may show no mosaic to slight mosaic symptoms. Pods may exhibit a slight mottling appearance. Seeds of infected plants may show slight brownish staining and/ or seed coat rupture (growth cracking). Seeds that look normal also may contain virus.
Cultural control
- Isolate introduced pea varieties and breeding lines from domestic nurseries and seed-increase fields.
- Monitor principal or all seed lots for seedborne virus and destroy infected seed lots or divert them to nonseed use.
- OSU has released resistant garden pea types.
Chemical control Apply systemic aphicides to nursery and small-increase plantings. See PNW Insect Management Handbook for details.