Post-harvest application of diphenylamine wettable powder and emulsifiable concentrate on Starking apples

Abstract

SummaryStarking apples, harvested at three stages of maturity and inoculated by immersion with 50 000 conidia of Penicillium expansum ml−1, were treated with chlorine, thiabendazole (TBZ) and diphenylamine, (DPA) (2 w.p. and 3 e.c. formulations) in a factorial experiment. The DPA content of each suspension was determined after treatment, and DPA residues in fruit were regularly determined. After storage (5 months at −0.5°C, 1 week at 10°C), superficial scald, DPA injury and wet core rot incidences were recorded. The DPA content of DPA e.c.s remained unchanged, but that of w.p.s decreased during treatment to 75% or less of the origianl concentration. Fruit treated with w.p. had higher DPA residues than those treated with e.c. Wettable power 1 and e.c. 3 controlled scald most effectively and caused least injury. DPA formulation did not affect the development of wet core rot and chlorine and TBZ decreased the incidence. Provided the correct formulation is used, Starking apples can be treated with DPA e.c. wi...