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Pseudomonas lachrymans Adsorption, Survival, and Infectivity Following Precision Inoculation of Leaves. Jerry H. Haas, Agriculture Canada, Research Station, Harrow, Ontario, N0R 1G0, Canada, Present address: Dept. of Plant Pathology, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel; Joseph Rotem, Dept. of Plant Pathology, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. Phytopathology 66:992-997. Accepted for publication 12 January 1976. Copyright © 1976 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-66-992.

Precise quantities of Pseudomonas lachrymans suspensions were deposited on leaf surfaces and the effects of drying and other factors were measured. Assay of survival was by dilution plating of wash water and by direct counts of infections on the inoculated leaves. Both techniques had a minimum detection level of about 1,000 cells per leaf. Over a range of 104 to 1011 cells/4 cm2 a constant proportion (93%) of the inoculum was adsorbed, indicating nonspecific adsorption sites. During a 16-hour post-inoculation drying period, survival was highest on pubescent suscept (cucumber) leaves, less on pubescent nonhost (potato) leaves, and least on glaborous nonhost (pear) leaves; both leaf surface morphology and innate plant resistance influenced the death rate. The pathogenís resistance to dry conditions governed survival on all three crops after the initial drying period; death rates were similar on all three crops. On cucumber, survival after drying for up to 16 hours was less at 10 C than at 25 C. With increasing periods of artificial dew on leaves before inoculation, short-term survival of the pathogen decreased.

Additional keywords: epidemiology, cucumber, angular leaf spot, leaf surface.