204 Minnesota Plant Diseases. 



both branches of this new agricultural machinery must work to- 

 gether in order to achieve successful results. The facts of ac- 

 tion and nature of diseases are useless unless applied and the 

 application of such knowledge is in the province of the plant 

 growers. In a word, the field of the plant pathologist is the 

 enlargement and spread of knowledge of diseases and their 

 causes and the field of the farmer is the application of such 

 knowledge to the raising of plants. Both parts of the machin- 

 ery of this new agriculture must work in harmony or both be- 

 come useless. The successful plant grower must not only know 

 what to do for certain diseases but why he does it, and the 

 pathologist only can tell him why. On the other hand, the 

 pathologist must look to the farmer for the solution of the 

 countless problems of practical detail in the application of that 

 knowledge. 



Every one knows that the best way of fighting off disease 

 in man — as in typhoid, tuberculosis, etc. — is to prevent infec- 

 tion, and just so with plant diseases. Prevention is the most 

 successful treatment of disease. But how can a disease be pre- 

 vented unless one knows the nature of the disease? It must 

 not be supposed that no relief is possible from actual disease in 

 plants for much can be done to furnish such relief but it needs 

 no argument to convince a fair-minded grower of plants that 

 prevention is more to be desired than methods of cure. It will 

 therefore be convenient to consider the methods for combating 

 disease under the two heads of prevention and cure. 



Prevention. Since prevention is of such great importance 

 it is obvious that a disease must be anticipated — headed off — 

 before it can get a start. Now the first stage of a fungus dis- 

 ease lies in the infection. Infection, as has already been point- 

 ed out, may be effected by fungus spores, as in rusts and smuts, 

 or by the established mycelium, as in timber and wood rots. 

 The prevention of infection is therefore first to be considered. 



Wound infection. A very common method O'f infection is 

 through wounds in plants. Wounds open up passages through 

 the outer layers of plant tissues which ordinarily resist the at- 

 tack of fungus threads and through these passages the threads 

 gain entrance. Plants have methods of covering such wounds 

 with cork or callous tissues but these methods are slow and be- 



