i8 



As the season advances and the host plant becomes 

 less active in supplying the amount of food required by 

 the fungus, summer spores cease to be produced, and in 

 their place winter spores are formed. Winter spores 

 differ as much in structure and general appearance from 

 summer spores as a pea does from a turnip. Their use 

 to the fungus is also totally different. They will not 

 germinate until after a considerable period of rest, in 

 fact not until the spring following their production. In 

 the spring, when Rose leaves appear, the winter spores 

 present on the patches of white mycelium that grew on 

 Rose stems the previous season, escape into the air, and 

 those that happen to alight on young Rose leaves set up 

 infection, which results in the production of that form of 

 the fungus which bears summer spores. 



From the above brief account of the mode of life 

 of Rose mildew, it is obvious that two special methods of 

 treatment are necessary to successfully combat this pest. 



(1) Spraying as soon as the leaf buds expand to 

 prevent infection by the winter spores. 



(2) In spite of spraying, a certain amount of 

 mildew will probably establish itself, more especially on 

 the young growth. To prevent this from setting up 

 infection the following season, all winter spores present 

 on the new wood should be removed. Details on this 

 point will be given later. 



(3) All bushes that have been attacked^by any kind 

 of fungus whatever should be thoroughly drenched with 



