Why Do My Grapes Have Sunken Dark Spots?

Sunken, dark-bordered spots on grape berries — often described as bird's-eye spots because of their pale grey centre and dark ring — are the hallmark of anthracnose (Elsinoe ampelina), a fungal disease that also affects leaves and young canes. Anthracnose is most severe in warm, wet spring conditions and most commonly affects vines in regions with humid summers. Identifying it early allows you to manage it before it spreads to a large proportion of the crop.

Symptoms on berries, leaves, and canes

On berries, anthracnose produces circular, sunken spots with a dark brown or black margin and a light grey centre that often falls out, leaving a crater or hole — the classic bird's-eye appearance. On leaves, it causes small dark spots that may also drop out, giving a shot-hole effect. Young canes develop dark, elongated, sunken cankers that can girdle and kill the shoot tip. Infected shoots are sometimes described as having a scabby or scaly appearance.

When and why infection occurs

The fungus overwinters in infected wood and bark. Spores are released in rain splash during spring, infecting the soft, newly emerged growth during bud burst and early shoot extension. Cool (15–25°C), wet weather during spring provides ideal infection conditions. Once the season becomes drier and warmer and the tissue hardens, new infections slow significantly.

Pruning out infected material

During winter pruning, cut out any canes showing the dark sunken cankers of anthracnose. Make cuts well below the visible damage and disinfect secateurs between cuts. Removing infected wood reduces the reservoir of the fungus significantly. Do not leave prunings on the ground under the vine — remove and dispose of them away from the garden.

Copper fungicide at bud burst

A dormant spray of copper hydroxide or Bordeaux mixture applied just before or at bud burst is highly effective at reducing early season infection pressure. Repeat the application when new shoots are 5–10 cm long if wet weather persists. Copper sprays are approved for organic use. The timing — very early in the season when tissue is most vulnerable — is more important than the number of applications later in summer.

Improving canopy airflow

A dense, poorly ventilated canopy stays wet longer after rain and provides the humid microclimate that anthracnose spores need. Keep the canopy open through training and summer pruning, position the vine in a site with good natural air movement, and avoid overhead watering. These practices do not eliminate the disease but measurably reduce its severity year on year.