Colorado Plant Diseases 
By JULIAN G. LEACH 
Assistant in Botany 
INTRODUCTION 
Few people realize the extent of the loss caused by plant dis- 
eases. The casual observer is often unaware of the presence of dis- 
ease in his fields. Furthermore, when the disease is known to be 
present the damage is usually underestimated. The United States 
Department of Agriculture, as a result of a nation-wide survey, esti- 
mated that in 1917 there was a loss of 64,344,000 bushels of wheat 
due to disease. This loss amounted to nearly ten per cent of our 
total production for the year. In the same year, which was not an 
especially serious one, the potato crop was reduced 117,174,000 
bushels, or a little more than one-fourth of the entire crop. The 
corn crop suffered a loss of 175,344,000 bushels. Other farm crops 
were reduced in similar proportions. In Colorado alone the injury 
to farm crops from plant diseases amounted to nearly $10,000,000. 
These figures are sufficient to convince anyone that every person 
who is in any way interested in crop production should be able to 
recognize the diseases that cause such an enormous loss and should 
know how to successfully combat them. 
The purpose of this bulletin is to furnish to the people of Colo- 
rado such information as will enable them to understand the nature 
of plant diseases, to recognize them as they occur in the field, garden 
or orchard, and to apply the best and most effective control 
measures. 
For convenience, the bulletin has been arranged in three parts. 
Part I gives, in simple, non-technical language, something of the 
nature of plant diseases and the agencies which produce them. 
Part II deals with specific diseases of Colorado crop plants. The 
crops have been arranged alphabetically and the diseases of each 
are treated in order of their relative importance. A few diseases are 
described which do not occur in Colorado, but on account of their 
serious nature and the importance of keeping them out of the state 
it has been thought advisable to include them at this time. Part III 
treats of the general principles of plant disease control and gives 
rules and formulae for the preparation and application of standard 
sprays and solutions for seed treatment. 
A bibliography has been added for the convenience of those who 
may desire further information concerning the diseases described. 
