Backyard Grapes Identify & treat grapevine problems
Fungal high severity

Eutypa dieback

Eutypa lata

A slow trunk disease ("dead arm") that stunts spring shoots and kills cordons one arm at a time.

Eutypa dieback: stunted shoots and cupped, chlorotic leaves on a grapevine Photo: Wine Australia Wine Australia
Symptoms of Eutypa dieback in (A) vine leaves and (B) new vine shoots Photo: Andolfi A., Mugnai L., Luque J., Surico G., Cimmino A., Evidente A. (2011), Toxins 3(12):1569-1605, Figure 1 Toxins (MDPI) via PubMed Central CC BY 3.0

Description

Eutypa dieback, the classic “dead arm” of grapes, is caused by Eutypa lata. Spores released during rain land on fresh pruning wounds and slowly colonise the permanent wood. The maddening part is the lag: a vine infected this winter may not show stunted, cupped shoots for two or three more years, by which time the canker is deep in an arm.

Because the fungus lives inside the wood, no spray reaches it. Control is really wound management — prune late and dry, seal big cuts, and when an arm is clearly declining, cut it out below the canker and grow a replacement from a clean sucker. Eutypa and the other trunk diseases (esca, Botryosphaeria) overlap heavily; a cross-section showing a wedge of dead wood is the giveaway that a trunk disease, not a leaf problem, is at work.

What to look for

  • Stunted spring shoots with small, cupped, tattered, yellowish leaves — often on just one arm.
  • A wedge-shaped dark canker in the wood, seen in cross-section near an old pruning wound.
  • Affected cordons or arms weaken and die back over several seasons.
  • The rest of the vine can look healthy while one arm declines.

Treatment options

Cultural & prevention

Start here — habits that stop problems before they spread.

  • Prune late in the dormant season, in dry weather, when wounds seal fastest.
  • Cut infected arms well below the canker, back into clean, healthy wood.
  • Retrain a new trunk or cordon from a healthy sucker below the diseased area.
  • Protect large pruning cuts with a wound sealant or paste.

Organic / low-toxicity

Gentler sprays and biologicals for active outbreaks.

  • There is no cure once the fungus is in the wood — sanitation and wound protection are the tools.

Conventional fungicide / pesticide

For severe cases. Always follow the product label.

  • Fungicidal wound-protectant products painted on fresh pruning cuts, where available.

Sources

This entry is based on the references below. Read them for full detail and for spray timings and rates valid where you live.

  1. Eutypa Dieback — UC IPM
  2. Eutypa Dieback of Grape — Ohio State University Extension (Ohioline)
  3. Eutypa and grapevine trunk disease — Wine Australia