Pest and Beneficials Search (search again)

Rusty spot

Podosphaera leucotricha (Ellis & Everh.) E. S. Salmon

Lesions begin as small, circular, tan to orange blemishes approximately 3–5 mm in diameter. The discoloration is due to discoloring of the fuzz on the fruit (A). As lesions enlarge, the interior, reddened fuzz is shed. At this point, lesions appear green and smooth, surrounded by a tan to orange halo. Lesions may continue to expand and may coalesce with other lesions to form larger smooth patches of infection. Eventually, lesions stop expanding, harden, and turn orange-brown.


Widespread; the disease occurs wherever powdery mildew of apple occurs.

Similar Species

Rusty spot can be confused with powdery mildew infection caused by Sphaerotheca pannosa (Wallr.:Fr.) Lév.or Podosphaera clandestine (Wallr.:Fr.) Lév.


Fungicide programs targeted for control of brown rot or peach scab will often provide appreciable control of rusty spot. Programs geared specifically for powdery mildew control will also be effective. Rusty spot is caused by the same fungus that causes powdery mildew on apple. Therefore, controlling powdery mildew infections on neighboring apple trees will reduce the incidence of rusty spot.

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.