Some factors affecting the rotting of stored apples by Gloeosporium spp

SUMMARY The susceptibility to rotting by Gloeosporium spp. of fruit from sixty‐two Cox's Orange Pippin apple trees on two plots has been found to vary from tree to tree and from year to year. There are indications that the level of inoculum released each year also varies. Examination of pruning snags and old fruiting spurs from one of these plots showed that 6% were infected with either G. perennans or G. album. Of 650 pruning cuts made in the winter of 1957‐58, 19 % subsequently became infected with Gloeosporium spp. Changes in the susceptibility of apples during a 2‐week period at harvest time markedly affected the incidence of rotting in store. No differences were found in the rates of spread of G. perennans in the cortical tissues of Cox's Orange Pippin apples of different sizes following inoculation. Germination of G. album on the surface of the apples is followed by a slight swelling of the tip of the tube germ, but no evidence has been obtained that this swollen tip functions as an appressorium. Inoculations of single lenticels with suspensions of spores of G. album in apple juice were relatively more successful than inoculations using aqueous suspensions, but little more than half of the inoculations were successful. Inoculations of the cortical tissues were also only partly successful and, for either method, the ease of infection was not found to increase with increasing maturity of the fruit.