Union Necrosis and Decline
Tomato ringspot
12 host plants
Last updated
This profile contains verified disease data from extension databases. Regional field notes and expert review are in progress.
Apple trees show unthrifty growth, abnormally high fruit set, and a dark necrotic line at the graft union when infected with tomato ringspot virus. The virus spreads via dagger nematodes in eastern North America and occasionally in other regions. Plant virus-tested trees in disease-free sites. Roguing young orchards prevents further spread.
Primary control is by planting virus-tested (and found to be free of all known viruses) trees and in sites that have no history of the disease.
Quick Reference
Management
Entire root systems are continuously vulnerable to nematode transmission of TRSV throughout the growing season when dagger nematodes are active in soil. Young trees are vulnerable at planting through maturity. Nursery propagation stock is vulnerable if obtained from TRSV-infested soil. Trees show delayed symptom development until reaching fruit-bearing stage, but virus is present and accumulating in tissues throughout this period.
Symptoms do not appear until infected trees approach fruit-bearing age (typically 3-5 years post-infection). At that time, trees exhibit unthrifty growth with abnormally high fruit set. Additional symptoms include reddish coloration of leaves and bark. In severe cases, a dark necrotic line appears at the graft union flanked by spongy orange tissue. Tree decline accelerates once symptoms develop. Symptom severity varies by cultivar, rootstock, virus strain, and nematode population density.
Cultural Controls
- Practice good weed management, as many weeds are reservoirs of TRSV and Xiphinema americanum. Test soil for presence of dagger nematodes before planting and avoid TRSV-infested sites if possible. Use TRSV-tested nursery stock from reliable sources. Control weeds in and around plantings to remove virus reservoirs. Manage nematode populations through cultural practices (crop rotation, green manures, resistant crops). Remove severely infected trees if detected early in plantings. Source: PNW Plant Disease Management Handbook