FUNGOUS DISEASES AND SPRAYING 



H. H. LAMSON 



It is important to liave a clear idea of the nature of fungous 

 diseases. The impression we have received in talking with 

 many upon the subject would seem to warrant beginning with 

 the statement that : Fungous diseases are not caused by insects. 

 They are caused by the groiuth of one pZa?i^ iipon another. 

 The plant which causes the disease is called a parasite and 

 belongs to the class of plants known as fungi. These parasites 

 are microscopic in size, so that it is not strange that their na- 

 ture is not generally familiar. The plant on which the parasite 

 grows and produces disease is called the host plant. Most of 

 the agricultural plants serve as hosts for several or many dif- 

 ferent species of fungi and are seriously injured thereby. 

 Figures might be given which would show that the aggregate 

 loss to agriculture from this cause is enormous. 



A fungus, like other plants, consists of a nutritive or vegeta- 

 tive part and a reproductive part. The vegetative part, in 

 fungi called mycelium, grows on or in the tissues of the host 

 plant and draws its food from them just as the host gets its 

 nourishment from the soil, and in so doing produces the injury 

 which constitutes the disease. Upon the vegetative part there 

 develops sooner or later the reproductive part, consisting of 

 spores and structures on or in which they are produced. The 

 spores perform the same office for the fungus that seeds do 

 for the host plant ; they are produced in great numbers and 

 are scattered by the wind. 



The fundamental principle in the treatment of fungous 

 diseases is to prevent the infection of the host plant by the 

 spores. The most practical way of doing this is to apply to 

 the plant to be protected some subtance which will kill the 



