Pilot Tests for Commercial Production and Application of Bacillus subtilis (B-3) for Postharvest Control of Peach Brown Rot. P. L. Pusey, Research Plant Pathologist, USDA-ARS, Southeastern Fruit and Tree Nut Research Laboratory, P.O. Box 87, Byron, GA 31008. M. W. Hotchkiss, H. T. Dulmage, R. A. Baumgardner, E. I. Zehr, C. C. Reilly, and C. L. Wilson. Research Technologist, USDA-ARS, Southeastern Fruit and Tree Nut Research Laboratory, P.O. Box 87, Byron, GA 31008; Research Microbiologist, USDA-ARS, Subtropical Crops Insects Research, P.O. Box 1033, Brownsville, TX 78520; Professor, Department of Horticulture, and Department of Plant Pathology and Physiology, Clemson University, Clemson, SC 29631; Research Plant Pathologist, USDA-ARS, Southeastern Fruit and Tree Nut Research Laboratory; and Research Plant Pathologist, USDA-ARS, Appalachian Fruit Research Station, Route 2, Box 45, Kearneysville, WV 25430. Plant Dis. 72:622-626. Accepted for publication 8 February 1988. 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, 1988. DOI: 10.1094/PD-72-0622.

The potential of Bacillus subtilis for postharvest control of peach brown rot caused by Monilinia fructicola was assessed in pilot tests on simulated commercial packing lines at Byron, GA, and Clemson, SC, and in a commercial packinghouse in Musella, GA. Because disease pressure was low due to drought conditions (1986), inoculum was introduced either in the dump tank water or as a spray onto the fruit after treatment on the line. Strain B-3 of B. subtilis was cultured in nutrient-yeast-dextrose broth (NYDB) in flasks at Byron or in another medium contained in a 250-L fermentor at Brownsville, TX. Nutrient broth was replaced by cottonseed flour as the primary source of nitrogen in the fermentor. This medium was low in cost, suitable for commercial use, and yet supported antibiotic production in culture, as did NYDB. In packing line tests, the number of colony-forming units of the bacterium added to each fruit was between 2 × 10⁷ and 7 × 10⁷ for B-3 from flask cultures and approximately 2 × 10⁹ for B-3 from the fermentor culture. In a test at Byron, B-3, cultured in flasks and applied fresh or after being stored (as paste or powder), was equal to benomyl (1–2 ppm residue in fruit) for brown rot control. In a similar test at Clemson, stored forms of B-3 from both flask and fermentor cultures were as effective as benomyl. In the packinghouse, B-3 produced at Byron approached benomyl for disease control, whereas that produced in the fermentor had no effect. However, an inability to completely remove fungicide residues from equipment in the packinghouse and the need to spray-inoculate fruit twice with the pathogen introduced unusual circumstances.