Conidial and ascospore germination of Uncinula necatorn, the causal agant of grape powdery mildew, was studied at different temperatures and, in different relative humidities. The results indicated that ascospores germinated on dry microscopic slides (at saturation humidity in a rang) of 5-30?C. Maximum germanation of ascospores (37 %) occurred at 25?C. Optimum germination was measured at a range of 20-30?C. Ascospore germination at 25?C on dry microscopic slides and at 100, 95, 76 and 54 % relative humidities were found to be 37% , 4.5 %, 0 % and 0 % , respectively. The conidia germinated over a wide range of temperatures and relative humidities on either of dry microscopic slides or grape leaves. Minimum temperature for conidial germination was 6?C with 21?C being optimum temperature for germination at saturation humidity. Conidia could germinate in between 54 to 100 % r.h at a range of 5-35?C. On grape leaves, conidial germination occurred under 100 %r.h and at a range of 5-35 ?C. Maximum conidial germination on leaves took place at 15 and 25?C.
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