VIEW ARTICLE

Biological Control

Antagonism of Selected Bacterial Strains to Stemphylium vesicarium and Biological Control of Brown Spot of Pear Under Controlled Environment Conditions. Emilio Montesinos, Food and Agricultural Technology Unit-CeRTA and Department of EQATA, University of Girona, 17071 Girona, Spain; Anna Bonaterra(2), Yakir Ophir(3), and Steven V. Beer(4). (2)Food and Agricultural Technology Unit-CeRTA and Department of EQATA, University of Girona, 17071 Girona, Spain; (3)(4)Department of Plant Pathology, Cornell University, Ithaca, NY 14853. Phytopathology 86:856-863. Accepted for publication 22 April 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/Phyto-86-856.

Over 410 strains of Erwinia herbicola and Pseudomonas fluorescens were isolated from aerial plant parts and roots of several crops, and of these strains, 7% inhibited germination of conidia and mycelial growth of Stemphylium vesicarium. Among the inhibitory strains, only four were highly effective against brown spot of pear in a detached leaf assay. An inverse relationship was observed between disease severity and inhibition of conidial germination on the leaf surface. The most efficient strains were P. fluorescens, which exhibited chemotaxis toward germinating conidia and produced antifungal compounds in solid and liquid culture. Pear plants treated with P. fluorescens EPS288, the most active antagonist, and subsequently inoculated with conidia of S. vesicarium, showed significantly (P < 0.001) lower disease incidence (57% less) and severity levels (88% less) than nontreated controls under conditions conducive to brown spot disease development. A spontaneous rifampicin-resistant mutant of strain EPS288 survived relatively well under moist conditions but survived less well under a moist-dry-moist schedule.