Studies on strawberry mildew, caused by Sphaerotheca macularis (Wallr. ex Fries) Jaczewski*

摘要: SUMMARY Cross-inoculation trials have shown that Sphaerotheca macularis on strawberries is a specialized form of this fungus. Conidia germinated consistently well dry healthy leaf surfaces. Cardinal temperatures for germination conidia were 2°, 20° and 35° C., while infection sporulation not recorded below 5° 13° C, respectively. Conidia retained their viability periods up to 5 weeks at 0° C. in saturated atmosphere, short under more exacting environmental conditions. Low humidities, although injurious conidia, especially high temperatures, had no effect growth the fungus. Light too conidial development Free water lethal was wet surfaces. A diurnal periodicity spore liberation, with maximum afternoon, has been observed. Rain drastic dispersal, reducing numbers trapped very low levels. There steep falling gradient number spores both increasing distance height from source. Heavy shade, humidities between 60 80° F. conducive production perithecia. evidence show strawberry mildew heterothallic. Inoculation experiments perithecia do play any essential part life history