Terminology

The terminology used to classify virus diseases can be confusing as it often refers to the behavior of the virus in the vector rather than in the plant! The following notes may be useful:

• Congenital: Passed from an infected adult vector to its offspring so that they too become carriers.

• Non-persistent: An insect vector feeding on a plant infected with a non-persistent virus becomes capable of spreading the virus immediately. This capability is, however, of limited duration and the insect eventually becomes "clean" again.

• Persistent: An insect vector of a persistent virus remains a source of infection until it dies. However, a vector feeding on a plant carrying a persistent virus does not immediately become capable of transmitting the virus so the use of chemical sprays to control the vector can be effective in preventing the spread of the virus.

• Vector: An insect capable of transmitting a virus from one plant to another is known as a vector.

Bean Yellow Mosaic

Synonym - Several including canna mosaic, gladiolus mosaic.
Distribution - World-wide.
Hosts - Wide range including red and white clovers, gladioli, freesia, Robinia pseudacacia.
Vector - Aphids (many species). Also spread mechanically, rarely seed borne.
Nature - Non-persistent.
Symptoms - Seasonably variable. Mosaic, streak, fuzzy head and colour breaking.
Status - This virus is rare on sweet peas

Pea Enation Mosaic Virus

Distribution - Widespread, including UK, USA and Canada.
Hosts - Culinary pea, white clover and other leguminous plants.
Vector - Aphids. Also spread mechanically and probably seed borne.
Nature - Persistent, not congenital.
Symptoms - Translucent windows with enation in leaves and flowers, mosaic, puckering of foliage, stunting.
Status - This virus is quite common on sweet peas

Pea Mosaic Virus

Synonym - Common pea mosaic.
Distribution - World-wide.
Hosts - Red clover, broad bean and other leguminous plants, but not white clover.
Vector - Aphids. Also spread mechanically, not seed borne.
Nature - Non-persistent.
Symptoms - Systemic mosaic, with streak developing on stem. Mottling and chlorosis of foliage. Colour breaking on flowers and distortion of head of plant ("fuzzy head").
Status - This virus is quite common on sweet peas, spreads rapidly and is highly destructive.

Pea Seed-Borne Mosaic Virus

Synonym - Pea leaf roll mosaic.
Distribution - Widespread, including UK, North America, Australia and much of Asia.
Hosts - Leguminous and other plants.
Vector - Aphids. Also transmitted mechanically and is seed borne in certain hosts including the cullinary pea.
Nature - Non-persistant.
Symptoms - Vein clearing, rosetting, leaf rolling. Symptoms are transitory and are lost soon after infection.

Tomato Spotted Wilt Virus

Synonyms - Many, including dahlia ringspot.
Distribution - World-wide.
Host - Very wide variety of plants, including grasses, tomato and potato.
Vector - Thrips, mechanical, not seed borne.
Nature - Persistent, not congenital.
Symptoms - Very variable. Leaves show circular yellow spots, turning brown. Mosaic, wilting and colour breaking. Reddish brown streaks on stem. For more detailed information, click to go to the TSWV page.
Status - This virus is rare on sweet peas but may become more common.