| Armillaria
root rot affects many woody plants, including grapes. Vineyards planted
on old orchard sites or newly cleared forestland may be at risk. Aboveground
symptoms are stunted shoots, yellow or red leaves, wilting and premature
defoliation. Symptoms are most obvious in late summer, when vines may completely
collapse and die. White, feltlike fungal mats occur below the bark near
the soil line.
Infected
tissues have a distinct mushroomlike odor when moist. Black, shoestringlike
strands (rhizomorphs) may be present on bark and in the soil. In the fall,
clumps of golden-brown mushrooms may appear at the base of the vine.
The fungus spreads
to neighboring vines via root contact and rhizomorphs, resulting in distinctive
clusters of dead vines within the vineyard. Armillaria can survive for
years on dead roots and old tree and vine stumps in the soil. |
