α-Farnesene levels in the outer coating of developing fruit of ten varieties of apple were monitored at fortnightly intervals from fruit set to harvest. The compound was present in all varieties and the total amount on individual fruit increased with increasing fruit size. However, varieties differed in the levels of α-farnesene/unit area of apple skin, with two peaks evident in some varieties during the season. The relationship between varietal and seasonal variation in α-farnesene production and the ecology and behavior of codling moth adults and larvae is discussed.