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An actinomycete isolated from the rhizoplane of nitrogen-fixing nodules of Ceanothus velutinus was identified as a variety of Streptomyces griseoloalbus. Streptomyces griseoloalbus is a strong antagonist to three destructive root pathogens, Phellinus weirii, Fomes annosus, and Phytophthora cinnamomi, inhibiting all three on several culture media and preventing establishment of F. annosus on hemlock wood disks. The stability and longevity of the antimicrobial substance produced by it, its consistent effect on the pathogens on all substrates, its ability to colonize wood, and its ability to grow at 10 degrees C suggest biological control possibilities for this organism in the Pacific Northwest.

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A Gram-positive bacterium that inhibits several root-rot pathogens was isolated from alder forest soil on the Oregon coast. This organism, similar toBacillus cereus, produces in culture media a heat-stable, broad-spectrum antibiotic which inhibits growth of four important Northwest conifer root disease fungi:Phellinus weirii (Murr.) Gilbertson,Fomes annosus (Fr.) Cke.,Armillariella mellea (Fr.) Karst., andPhytophthora cinnamomi Rands.