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Title: CONTROL OF PHYTOPHTHORA ROOT AND CROWN ROT OF BELL PEPPER WITH COMPOSTS AND SOIL AMENDMENTS IN THE GREENHOUSE

Author
item KIM, K. - UNIV. OF FLORIDA
item Nemec Jr, Stanley
item MUSSON, G. - UNIV. OF FLORIDA

Submitted to: Applied Soil Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/22/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Phytophthora capsici occurs in the tropical, subtropical, and warm areas of the world and infects all parts of pepper including roots, stems, leaves, and fruits. Pepper root and crown rot caused by the fungus P. capsici is a destructive soilborne disease. Control of this disease widely had depended on methyl bromide. Methyl bromide will be phased out by January 1, 2001 in the U.S. because it depletes the ozone layer. The possible loss of methyl bromide will severely affect major vegetable producing states including Florida and California. Thus, alternatives to methyl bromide are being investigated. Composts and soil amendments have the potential to control this important pepper disease. Ten composts and soil amendments: calcium humate, calcium sulfate, chitosan, citrus pulp, citrus pulp with molasses, crab shell waste, humate, mustard residue, sewage sludge-yard trimming, and wood chips were tested in the greenhouse for control of pepper root and crown rot disease. Disease severity and stem lesion length were determined, as were final root and shoot dry weights. These research results show that chitosan, crab shell waste, and citrus pulp with molasses are promising treatments for controlling this disease of bell pepper.

Technical Abstract: Ten composts and soil amendments were evaluated in the greenhouse for control of Phytophthora root and crown rot of bell pepper caused by Phytophthora capsici. Three rates of calcium humate, calcium sulfate, chitosan, citrus pulp, citrus pulp with molasses, crab shell waste, humate, mustard residue, sewage sludge-yard trimming, and wood chips were incorporated into soil in pots prior to transplanting six-week-old bell pepper cultivar Early Calwonder. P. capsici zoospores (2 x 10**4) were placed into the soil of each pot 2 weeks after transplanting. Areas under the disease progress curves (AUDPC) for disease severity and stem lesion length were determined, and final root and shoot dry weights were also evaluated. Soil populations of five microbial functional groups, and total microbial activity, measured by fluorescein diacetate hydrolysis analysis, were evaluated. Certain rates of chitosan, crab shell waste, and citrus pulp with molasses significantly reduced AUDPC for disease severity and/or stem lesion length, and increased root or shoot dry weights, compared to unamended controls. None of the other treatments were effective in reducing root and crown rot of bell pepper. Citrus pulp with molasses was unique in enhancing the total microbial activity and populations of certain microbial functional groups, compared to unamended controls.