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Encapsulation of Potential Biocontrol Agents in an Alginate-Clay Matrix. D. R. Fravel, Research plant pathologist, Soilborne Diseases Laboratory, Plant Protection Institute, U.S. Department of Agriculture, Beltsville, MD 20705; J. J. Marois(2), R. D. Lumsden(3), and W. J. Connick, Jr.(4). (2)(3)Research plant pathologists, Soilborne Diseases Laboratory, Plant Protection Institute, U.S. Department of Agriculture, Beltsville, MD 20705, (2)Present address: Department of Plant Pathology, University of California, Davis 95616; (4)Research chemist, Crop Protection Research Laboratory, U.S. Department of Agriculture, New Orleans, LA 70179. Phytopathology 75:774-777. Accepted for publication 25 February 1985. 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, 1985. DOI: 10.1094/Phyto-75-774.

A method to encapsulate microorganisms that have potential to control plant diseases was tested. Aqueous solutions containing 1% sodium alginate and 10% Pyrax^® were comminuted in a blender. Solutions were amended singly with either ascospores or conidia of Talaromyces flavus (isolate Tf1 or Tf1-I); conidia of Gliocladium virens (isolate GL3), Penicillium oxalicum, or Trichoderma viride (isolate T-1-R9); or cells of Pseudomonas cepacia (isolate POP-SI). The alginate-Pyrax^®-propagule suspension was dripped through Pasteur pipettes into a solution of either 0.25 M CaCl₂ or 0.1 M Ca gluconate which caused the formation of solid aggregates. The aggregates were dried overnight and stored under room conditions. Populations of encapsulated organisms were estimated after 0, 2, 4, 8, and 12 wk by dissolving the pellets in a mixture of 8.7 x 10^-3 M KH₂PO₄ and 3.0 x 10^-2 M Na₂HPO₄, and dilution plating on semiselective media. All fungi, but not Pseudomonas, were viable after pellet formation in CaCl₂. All organisms were viable longer after pellet formation with Ca gluconate. Initial populations ranged from 10⁵ to 10⁸ propagules per milliliter of alginate suspension. These populations declined during the test period: losses were 10 to 100-fold after 4 wk.