Pierce's disease
Bacterium (Xylella fastidiosa), spread by sharpshooter insects
| Type | Bacteria |
|---|---|
| Cause | Bacterium (Xylella fastidiosa), spread by sharpshooter insects |
| When | Infection during the growing season; symptoms from midsummer through fall. |
About
A bacterial disease that clogs the water-conducting tissue of grapevines and eventually kills susceptible vines, especially European-type bunch grapes. It is spread by xylem-feeding sharpshooters and has no cure.
Also called Pierce's disease (Southeast), Pierce's disease
How to recognize it
Symptoms
Leaf edges scorch brown, leaf blades drop while the stems stay on the cane like matchsticks. Canes ripen unevenly, leaving green islands in brown bark, and grape clusters dry up into raisins. Symptoms appear around veraison and peak from late August into September.
Often confused with
Scorched leaf edges alone are not enough to diagnose it; look for the full set of symptoms and get a lab test to confirm.
Worse when
Mild winters, which let the bacteria and insect vectors survive; cold winters suppress the disease.
How it spreads
Sharpshooters (including the glassy-winged sharpshooter) and spittlebugs pick up the bacteria while feeding and carry them to healthy vines.
When
Infection during the growing season; symptoms from midsummer through fall.
Where
Common from Florida to Virginia and west through Alabama, Mississippi and Texas, and in California, where the glassy-winged sharpshooter became established in the 1990s; less common in cold-winter and high-elevation areas.
What to do, gentlest first
Prevention works best; most sprays only protect healthy leaves and can't cure infected ones. Always read and follow the product label.
Plant tolerant grapes where the disease is common Prevent
In mild-winter parts of the South, grow muscadines or tolerant bunch grapes such as Blanc du Bois, Norton, Lenoir, Villard blanc or Lomanto instead of European (vinifera) types.
Yellow sticky traps help you see whether sharpshooters are around; UGA suggests large double-sided cards at least 4 by 7 inches, checked weekly. In California, have nursery stock inspected before moving it out of southern California.
Remove infected vines By hand
Pulling out infected vines is the only sure fix. Annual dormant pruning of one-year canes can also remove some first-year infections.
Clean pruning tools with a 10% bleach solution.
Plants it affects
Sources
Planting dates and advice are general guidance; check with your local Cooperative Extension office for your area.