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Effect of Mineral Salts on Aphanomyces euteiches and Aphanomyces Root Rot of Peas. J. A. Lewis, Research Soil Scientist, Plant Protection Institute, Agricultural Research Center, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, Maryland 20705; Phytopathology 63:989-993. Accepted for publication 15 February 1973. DOI: 10.1094/Phyto-63-989.

Of the salts of 11 cations tested, only CuSO4 and FeCl3 at concentrations of 50 µg cation/ml or less almost completely inhibited growth, zoospore formation, and zoospore germination in Aphanomyces euteiches in vitro. The effects of the other cations (A1, B, Ba, Ca, Co, Mg, Mn, Mo, and Zn) on these processes were varied. The addition of A1, Ca, Cu, and Zn at concentrations of 50 and 100 µg/g of soil significantly reduced root rot of peas without apparent adverse effects on the plants. The cations were effective in combination with various anions. Most of the salts, which included the chlorides, nitrates, phosphates, sulfates, and carbonates of A1, Ca, Cu, and Zn, significantly reduced pea root rot. Addition of a complete fertilizer to amended soil did not alter the effectiveness of the cations in disease reduction. The effectiveness of A1, Cu, and Zn was sustained throughout three pea plantings, but that of Ca was lost after the second planting. No additional benefit was derived from using A1, Cu, or Zn in combination with each other. Copper at 50 µg/g, or Cu at 25 µg/g in combination with either A1 or Zn at 25 µg/g, almost completely suppressed disease. Possible use of these materials in agriculture to reduce Aphanomyces root rot of peas is discussed.

Additional keywords: root-infecting fungi.