Infectious Diseases/Pathogens

 

Apple Scab: Apple scab appears as a dark, rough patch on the surface. Lesions that were initiated early in the season are large, and the fruit may be cracked, since the skin there can’t expand well as the fruit enlarges. Sometimes scab is restricted to the sepals. Sometimes lesions are very small, having been initiated in August by conidia splashed from nearby lesions on fruit or foliage.

Flyspeck: Group of small black dots on the skin. In severe cases, several groups of dots are apparent. This could be on any surface of the fruit; more common where humidity was high, like in dense foliage or hanging low into grass.

Sooty Blotch: Without magnification, sooty blotch looks like a gray spot (could be several) on the fruit surface. Viewed with a 10X lens, it looks like a series of black spots. It usually is in association with flyspeck.

Calyx End Rot: The calyx end of the fruit shows a black area. In some cases it is hard and dry; in others the rot is active and soft.

Bitter Rot: A rot with obvious concentric rings in the fruit. The rotted flesh is soft. I don’t see much of this.

Black Rot: This looks very similar to bitter rot; sometimes I can’t tell them apart. If I see a rotten area with concentric rings, surrounded by a reddish halo, I consider it black rot. The decayed flesh usually is firm, not soft.

Powdery Mildew: This is not very common in NH. A netlike pattern of russet could be from powdery mildew. I saw some in 2002, but have seen none since then.