Abstract
Tolerance to benomyl in the apple scab fungus Venturia inaequalis became evident in Noya Scotia 8 years after the fungicide was first recommended for use. Tolerant isolates were found inunsprayed as well as in benomyl-sprayed orchards. Two levels of tolerance were demonstrated in vitro. A new technique to demonstrate tolerance in which segments from a scab lesion were transferred onto potato dextrose agar (PDA) and PDA amended with benomyl was used to demonstrate tolerance is described.