Postharvest Biological Control of Stone Fruit Brown Rot by Bacillus subtilis. P. Lawrence Pusey, USDA-ARS, Appalachian Fruit Research Station, Route 2, Box 45, Kearneysville, WV 25430. Charles L. Wilson, USDA-ARS, Appalachian Fruit Research Station, Route 2, Box 45, Kearneysville, WV 25430. Plant Dis. 68:753-756. Accepted for publication 12 March 1984. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1984. DOI: 10.1094/PD-68-753.

Pseudomonas cepacia, P. fluorescens, Bacillus thuringiensis, and two isolates of B. subtilis (B-3 and B-1849) were tested in the laboratory for antagonism against Monilinia fructicola on wounded stone fruit. Peaches, nectarines, apricots, and plums were sprayed with bacterial suspensions, inoculated 1–2 hr later with spores of M. fructicola, then held in moist chambers at 18–24 C. Only the B-3 strain of B. subtilis controlled brown rot on all fruit types. When varying concentrations of B-3 were tested on peaches, brown rot development was retarded by 10⁶ and 10⁷ colony-forming units per milliliter. At 10⁸, fruit did not become infected with M. fructicola but decayed after 9 days because of other fungi. Strain B-3 reduced decay regardless of the inoculum level or the isolate of M. fructicola tested and was effective at temperatures of 10–30 C. The mechanism of B-3 activity appears to involve production of an antifungal substance, since the culture filtrate protected fruit from rot. The filtrate retained activity after being autoclaved at 15 psi and 120 C for 15 min.

Keyword(s): bacterial antagonist.