THE EFFECT OF TEMPERATURE AND HUMIDITY ON THE TOBACCO POWDERY MILDEW FUNGUS
ARMY BIOLOGICAL LABS FREDERICK MD
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The influence of temperature on the germination of conidia and on the infection of tobacco by powdery mildew was determined. For the former the minimum, optimum and maximum temperatures were found to be lower than 5C between 24-25C and between 30-35C, and for the latter 5, 23.5 and 25C respectively. The existence of a very close correlation between the occurrence of powdery mildew in certain tobacco areas and the average daily maximum-minimum temperatures prevailing in those areas could be shown. It was found, for example, that powdery mildew did not occur in areas in which the prevailing average daily maximum-minimum temperatures were 25C or higher. Relative humidity on the other hand, has much less influence than temperature on either the germination of the conidia or the occurrence of powdery mildew in different tobacco areas. It was found, for example, that the conidia could germinate under conditions in which the R. H. varied from 0 to 100 percent between temperatures of 15 and 30C. Furthermore, no correlation between R. H. and the occurrence of powdery mildew could be found.
- Anatomy and Physiology