Scab-resistant Apple Varieties
These varieties have been bred genetically for immunity to this pathogen. As a result, fungicides are not needed to control apple scab throughout the growing season. Scab-resistant apple varieties are, however, susceptible to the summer fruit diseases, including black rot, white rot, bitter rot, sooty blotch, and flyspeck, and they vary in susceptibility to cedar apple rust, powdery mildew, fire blight, and leaf spots. In certain regions and summers, sooty blotch and flyspeck can cause extensive fruit blemishing. These blemishes are only superficial and can be partially rubbed off. They cause the fruit to look unsightly but do not affect taste. These two diseases can be minimized by training and pruning the trees to increase air circulation and reduce humidity in the canopy.
None of the scab-resistant apple varieties are completely immune to cedar apple rust. Even those rated as rust resistant will need fungicide protection from rust if they are planted adjacent to cedar trees that harbor this pathogen. It is advisable to remove the cedar trees if possible. To ensure high fruit quality, fungicides still will be required on scab-resistant varieties; however, fewer will be needed than on highly scab-susceptible varieties such as Empire, McIntosh, and Red Delicious. The number of fungicides applied on scab-resistant varieties also will depend on the particular season, especially if it is extremely wet.
Scab-resistant apple varieties are excellent choices for the home garden and backyard farmer. The fruit are of reasonable quality and can be produced with only a few pesticide applications each year. These varieties make harvesting fresh apples from late July through October possible (Table 4.1).