ISSN: 0041-3216

ISSN: 0041-3216 (Online), 0041-3216 (Print)
Volume 49 Number 3
Research Papers
Germination and survival of conidia of Cercospora canescens Ellis et Martin
Germination of conidia of C. canescens was completely inhibited by CuS04 and FeCI2 at 0·001 M, K2HP04 and (NH4) 2HP04 at 0·1M and by MnS04. 2H20 and a NaCl at 0·5 M. Distilled water supported 100 per cent germination at the optimum temperature, 25°C, the conidia producing germ tubes from both end cells and from not more than three median cells. The number of median cells able to form germ tubes was reduced by extreme temperatures, 15° and 35°C, and very acid pH (pH 3·5) and increased by host leaf exudate and several organic compounds. The conidia survived longer at 20° than at 28°C. In dark, the conidia lost viability sooner at high storage humidities than at low, whereas conidia exposed to light survived longer at median humidities close to 40 per cent RH than at high and low humidities.