38 STATE POMOLOGICAL SOCIETY, 



Perithecia which are not in condition to allow ejection of 

 spores during a given rainy period are apt to ripen during the 

 following warm days and be ready at the next period of rain 

 for spore ejection. Thus it may happen and frequently does 

 that new infections at favorable periods are continually recur- 

 ring, both from the leaves on the ground and from earlier 

 infected leaves on the tree. 



So it goes throughout the season. Rainy weather followed 

 by periods of calm, foggy weather, permit new infections to 

 occur. When we have a dry summer, as not infrequently 

 happens, many spores are produced which perish for the want 

 of moisture, but with the occurrence of fall rains, sufificient 

 spores are found to be in a viable condition to cause further 

 infection, as many of you know only too well. 



Philosophy of Disease Control. 



Spray Before the Rain, Not After. From what I have said 

 you will see that it is coming to be understood generally, by 

 men who have fungous diseases to fight, that any fungicide 

 to be at all effective must be one that will adhere to the foliage 

 during periods of prolonged rainy weather and, above all, that 

 fungicides must be applied to the parts attacked before the 

 conditions arrive which make spore germination possible. It 

 is believed that more failures to control apple scab and man> 

 other fungous diseases are attributable to the failure to recog- 

 nize this one point than to any other cause. It is, therefore, 

 worthy of repetition, that any fungicide, to be at all effective, 

 must be one that will adhere to the foliage during periods of 

 prolonged rainy weather, and that, above all, fungicides must 

 be applied to the parts attacked before the conditions arrive 

 which make spore germination possible. 



Weather Forecasts. I presume many of you are already 

 wishing to ask the secret of predicting rain periods and, in 

 order not to arouse your hopes, I wish to say at once we have 

 no way of telling certainly whether rain will occur or not. We 

 have, however, a very effective way of determining whether 

 atmospheric conditions are such as to permit rain to fall if 

 there is moisture in the clouds. This service is free to every 

 person in the United States. I refer to the weather reports 



