Pest and Beneficials Search (search again)

Blister spot

Pseudomonas syringae pv. Papulans (Rose 1917) Dhanvantari 1977

Lesions begin as small, darkened, water-soaked areas, generally around lenticels and typically on the lower half of the apple. Small raised blisters form shortly thereafter, becoming purplish black as they expand (A). The infections are shallow, not extending more than 1–4 mm into the fruit flesh. The epidermal layer covering the blister dies and will often flake off the surface (B). The lesions are generally circular and rarely become larger than 4–5 mm in diameter. Leaves of Mutsu may also experience a mid-vein necrosis (C).

Distribution

Economically damaging only on the variety Mutsu (Crispin).

Similar Species

None

Management

Blister spot is managed primarily through the timely application of bactericides during the three weeks after petal fall.

Pest and Beneficials Search (search again)

The MSU IPM Program maintains this site as an access point to pest management information at MSU. The IPM Program is administered within the Department of Entomology, fueled by research from the AgBioResearch, delivered to citizens through MSU Extension, and proud to be a part of Project GREEEN.