Effect of Temperature on Incidence and Development of Bitter Rot Lesions on Apples. James P. Noe, Graduate Student, Department of Plant Pathology and Plant Genetics, University of Georgia, Athens 30602. Thomas E. Starkey, Assistant Professor, Department of Plant Pathology and Plant Genetics, University of Georgia, Athens 30602. Plant Dis. 64:1084-1085. Copyright 1980 American Phytopathological Society. DOI: 10.1094/PD-64-1084.

Bitter rot of apples, caused by Glomerella cingulata, is destructive in orchards of the southeastern United States. Development of the disease is linked to periods of high temperature and rainfall. Mature apples were washed, rinsed, spray-inoculated, and incubated in moisture chambers at 22, 26, 28, 30, and 34 C. Total lesion area (> 1 mm²) and the number of lesions were determined 12, 15, and 18 days after inoculation. No infection occurred at 34 C or in controls. The highest percentage of apples was infected at 26 C and the lowest at 30 C. The greatest number of lesions occurred at 26 C. The median lesion area was greatest and the lesions expanded most rapidly at 30 C. Thus, the optimum temperature for lesion expansion was 30 C.

Keyword(s): Colletotrichum gloeosporioides, epidemiology.