Honeycrisp leaf yellowing showing up on Michigan apples
Leaf yellowing on Honeycrisp apples looks severe, but seems to have no detrimental effect on the trees.
During July and August, Honeycrisp will develop leaf yellowing that in some years can be quite severe (Photo 1). This disorder is a genetic characteristic of Honeycrisp and is caused by excessive buildup of carbohydrates in the leaves. Yellowing is greatest on light crop load trees and limbs where there is no fruit to collect the carbohydrates from the leaves. The excessive carbohydrates cause the reduction of photosynthesis and leaf chlorophyll levels declines, turning the leaves yellow. This yellowing seems to have no detrimental effect on the trees, but looks severe. Some other varieties can get this yellowing (Photo 2), but this leaf yellowing also resembles leafhopper burn – Honeycrisp leaf yellowing is not caused by leafhoppers.