Influence of Temperature, pH, Osmotic Potential, and Fungicide Sensitivity on Germination of Conidia and Growth from Sclerotia ofColletotrichum coccodesin Vitro

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Abstract
Germination of conidia of Colletotrichum coccodes was greatest at 22 C after 24 hr. Conidia did not germinate at 7 C after 24 hr and <70% of the conidia germinated at 10 or 31 c. Growth rates of cultures started with air-dried selerotia were greatest at temperatures from 25 to 31 C. Germination of conidia and growth from sclerotia were optimum at pH 6. Water agar was osmotically adjusted using either KCl, NaCl, CaCl2, or sucrose. Maximum germination of conidia and growth from sclerotia occurred at the highest osmotic potentials (-5 to -10 bars). Little or no germination of conidia occurred at -45 bars except when CaCl2 was used to adjust the osmotic potential of the medium. Radial growth from sclerotia was less than KCl or NaCl amendments were used than when CaCl2 or sucrose were used. Sensitivity of conidia and sclerotia to captafol, chlorothalonil, anilazine, mancozeb, and copper hydroxide were determined in vitro. Conidia were most sensitive to captafol, which significantly reduced their germination and germ tube elongation at concentrations of 0.01, 0.1, and 1 .mu.g a.i./ml. Sclerotia were also most sensitive to captafol, which significantly reduced growth at concentrations of 1, 10, and 100 .mu.g a.i./ml. Conidia and sclerotia were sensitive to chlorothalonil at the two highest concentrations tested (0.1, 1 .mu.g a.i./ml and 10, 100 .mu.g a.i./ml respectively).