VIEW ARTICLE

Ecology and Epidemiology

Influence of Controlled Environment and Age on Development of Alternaria macrospora and on Shedding of Leaves in Cotton. Esther Bashi, Division of Plant Pathology, Volcani Center, Agricultural Research Organization, Bet Dagan 50-250, Israel; J. Rotem(2), H. Pinnschmidt(3), and J. Kranz(4). (2)Division of Plant Pathology, Volcani Center, Agricultural Research Organization, Bet Dagan 50-250, Israel; (3)(4)Tropeninstitut, University of Giessen, Giessen, D-6300, W. Germany. Phytopathology 73:1145-1147. Accepted for publication 7 March 1983. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-1145.

Under controlled conditions disease development was 5.5- 8.9 times higher in cotyledons than in leaves. For infection of both organs the minimum, optimum, and maximum wetting-period temperatures were below 10 C, from 20 to 25 C, and 35 C, respectively. Cotyledons were substantially infected after a 4-hr wetting period, and temperatures of 20 and 25 C. Much longer wetting periods were required for infection of leaves. The minimum temperature for colonization was below 10 C (the lowest temperature tested) in cotyledons and 10 C in leaves; the optimum and maximum temperatures were 20 to 30 C and 35 C, respectively. Susceptibility in cotyledons increased with age up to 20 days, and decreased thereafter. In leaves, susceptibility slightly decreased with age. Shedding of cotyledons was affected mainly by age, which obscured the effect of disease. In leaves, increase in disease severity from 0 to 16% was correlated with shedding. The epidemiological implications of cotyledon susceptibility and of shedding are discussed.