Symptoms and Signs
On cherry trees infected by the rugose mosaic strain of the virus, necrotic ringspot symptoms occur early in the season and include yellowing, browning, and shot hole of leaf tissue. (Discolored areas on leaves may turn brown and leaves may drop early in the summer.) Enations develop from the underside of leaves near the midrib. Fruit may be deformed and may ripen later than normal. Additional symptoms include distorted growth, death of twigs, buds, or young foliage, and stunting of trees.
Comments on the Disease
The virus is spread in pollen and seed as well as via budding and grafting with infected wood. Thrips feeding is suspected to spread the virus from infected pollen into the tree; otherwise virus from infected pollen remains confined to the seed.
Management
To manage Prunus necrotic ringspot virus, use virus-free budding material and rootstock in nurseries and plant certified nursery stock in production orchards. Immediately remove trees that develop symptoms to prevent spread to other trees in the orchard. This is especially critical in blocks that are being used for scion wood. Mow or disc cover crops and weeds before stone fruits bloom in order to reduce the buildup of thrips populations on flowering weeds, as they may otherwise contribute to the spread of the virus.