Apple growers in Pennsylvania are reporting more necrotic leaf blotch on Golden Delicious and cultivars with Golden Delicious as a parent — Pink Lady, GoldRush, Gala, and Jonagold — according to Kari Peter, assistant professor in the Department of plant pathology and environmental microbiology and tree fruit pathologist with Penn State Extension.
This physiological disorder can appear overnight in the months of July and August and is more severe when cool, rainy weather is followed by very warm temperatures.
Stone fruit growers need to monitor for bacterial spot and fruit rot diseases, says Peter. The bacteria is still active, she cautions, thanks to cooler temperatures and milder weather.
Click here for management practices for necrotic leaf blotch, bacterial spot, and fruit rot disease as well as infection periods for apple scab, fire blight, cedar apple rust, cherry leaf spot, and sooty blotch and flyspeck.
Source: Penn State University Extension bulletin