Why Do My Grapevine Leaves Have Brown Spots?

Spotting on grapevine leaves is almost always a signal that something has damaged the leaf cells — whether from a fungal pathogen, an insect pest, physical scorch, or chemical burn. The shape, colour, and location of spots on the leaf can narrow down the cause considerably, and acting early prevents the problem from spreading to fruit and reducing your harvest. Take a close look at the spots before reaching for a spray.

Anthracnose — sunken dark spots with grey centres

Anthracnose (Elsinoe ampelina) produces small, roughly circular spots with a dark brown or black border and a pale ash-grey centre that often falls out to leave a shot-hole appearance. It spreads rapidly in cool, wet spring weather and can affect young canes as well as leaves. Remove affected material, apply a copper fungicide at bud burst the following spring, and improve canopy ventilation.

Downy mildew — brown angular patches

As downy mildew progresses past the initial oily yellow stage, affected patches die and turn brown. The angular shape (bounded by leaf veins) and the white fuzzy growth on the underside of matching areas are diagnostic. Downy mildew spreads fast in humid conditions. Apply copper hydroxide or mancozeb, remove badly affected leaves, and ensure the canopy is open enough for air to move through.

Leaf hopper damage — pale stippling becoming brown

Grape leafhoppers feed by puncturing leaf cells on the underside of the leaf. This produces a speckled, stippled appearance at first — thousands of tiny pale dots — that merges into larger brown areas as damage accumulates. Check the underside of spotted leaves for tiny, fast-moving pale insects. Yellow sticky traps and removing overwintering habitat (leaf litter, loose bark) reduce populations without chemical intervention.

Sunscorch on wall-trained vines

Vines trained against a south-facing wall or under glass can experience sunscorch in midsummer when light intensifies. Scorched areas appear as irregular pale-brown or bleached patches on the part of the leaf most exposed to direct sun. Unlike fungal spots, scorch patches lack a defined border and are dry rather than water-soaked. Providing light shading or ensuring adequate soil moisture reduces severity.

Fertiliser or spray burn

Applying foliar fertiliser or fungicide in hot sun, or at concentrations above those recommended, can cause chemical burn — small brown spots or necrotic margins that appear within a day or two of spraying. Always spray in the evening or on overcast days, and stick to label rates. Rinse foliage with clean water if a concentrated product was applied accidentally.