- Red vine in late summer
- no gophers (mounds), voles (holes around base), tractor damage, or blight
- Swelling above graft union and pitting/grooving on scion (girdle causes red leaves)
- Negative on virus panel.
Variation in symptom expression:
Clone susceptibility generally more important than rootstock.
Rootstock: Most symptomatic (99R, 110R), Least (5BB, Riparia (Gloire), 1103P, 101-14, 420A anecdotal)
rupestris in background may be a factor
Clones: Most symptomatic (73, 99, 301, 381, 382, 383), Intermediate or variably symptomatic (100, 174*, 300, 525, 585, 877**), Least (470, 471, 524, 747)
* Clone 174 was highly variable and was highly symptomatic in some tests.
**Clone 877 has been planted throughout Paso Robles and has been highly impacted by Syrah decline.
Filed under: pest and disease