23 



application. That means ordinary apple scab sprays won't 

 catch. 



Chairman Jenks. Sooty blotch is very bad with us in east- 

 ern Massachusetts. 



Professor Whetzell. Sooty blotch is a disease that comes 

 on relatively late, and you have got to get a mixture on ahead 

 of it, and probably a couple of them. 



Chairman Jenks. The question is asked, why is it better 

 to spray before rather than after rain? 



Professor Whetzell. Well, for exactly the same reason that 

 it is better to get inoculated for typhoid before you get it than 

 after. 



Here is the situation. Take the apple scab. The first infec- 

 tions in the spring are produced in the old leaves of last season 

 that lay on the ground, the scabby foliage of last year, that 

 fell to the ground this year. 



Those spores are shot from the old leaves, and then a breeze 

 catches them and carries them to the foliage, but they are only 

 shot out during rains, and they get on to the leaves only 

 during rains, and they germinate, and they go into the leaves 

 during that rainy period. 



In other words, to get apple scab infection on your early foli- 

 age, you have to have about forty-eight hours of rainy weather, 

 some rain for a period of about forty-eight hours, and you will 

 get infection. The fungus will be inside the leaf. If you have 

 no protection on the foliage, you can go if you want, after 

 the rain is over, and put it on the outside, but the spray mix- 

 ture does not operate to kill the fungus. 



In other words, spraying is a protection. . 



Now, some of you labor under the delusion that you spray 

 to kill something which is already there. You do not. You 

 put the spray mixture on to protect it from something that is 

 going to come, and that something comes during the rain. 

 Almost all fungi are either put on the leaf in the rain or germ- 

 inate only during a period when the surface is wet; therefore, 

 you must put protection on ahead and not after. 



Any other question? 



Chairman Jenks. Is it the opinion, Professor, that it is 



