The Relation of Thrips to Pansy Spot on Apples

Abstract

Pansy spot, a discoloration of the skin of McIntosh and Spartan apples, was shown to be a reaction of the apples to the egg punctures of thrips. Periodic sampling of apple blossoms and native hosts associated with apple orchards showed that Frankliniella occidentalis (Pergande) was the dominant species. The adult thrips moved from host to host as each came into flower, and apples were but one of several hosts attacked during the early spring.The thrips were most numerous in apple blossoms during the bloom period, and oviposited in the flower parts. The adult thrips left the apples after the bloom period, and the nymphs that hatched from the eggs developed in the calyx end of the young fruit. When the nymphs matured they oviposited in the young apple before leaving for other hosts. The area of apple skin surrounding the thrips egg developed the typical pansy spot symptoms. Other apple varieties were also attacked, but did not develop pansy spots.It was evident that the best time to apply control measures was at the petal fall period, when nymphal thrips were present but before damage was caused to the young apples.