54 STATE POMOLOGICAL SOCIETT. 



both classes — being parasitic at first and continuing to live after 

 the host has been killed. It is with the first class — parasitic fungi 

 — that we are especially interested at this time. 



Within the past fifteen years the number of plant diseases has 

 increased with alarming rapidity until there is scarcely a fruit or 

 vegetable which does not have its specific fungous enemies. 



What is the reason for this increase? First of all, perhaps, is 

 increased knowledge of the causes of many failures. Formerly 

 crops were injured or destroyed and the fact was accepted without 

 attempt at an explanation, or the blame was thrown on the moon 

 or the weather. Now the mycologist is called and with his 

 improved means of study, he is soon able to tell us the exact cause 

 and frequently the whole life history of the pest. 



Again, many of the parasitic fungi best known at the present 

 time originated on wild plants and on such were not considered of 

 special importance. When, however, some closely related plant in 

 garden or orchard was attacked, attention was at once arrested and 

 it was said a new disease had appeared, (e g. "black knot" of 

 plum and cherry, and "orange rust" of blackberry.) 



There are various ways in which parasitic fungi injure their host 

 plants ; and no part of the plant is exempt from attack, roots, 

 stems, leaves, flowers, and fruit, are all in danger. By far the 

 most common and important injury caused by the parasites is in 

 the appropriation of nourishment belonging to the host. This 

 results in the falling or deformity of fruit or leaves, according as 

 the attack is early or later in the season. 



Again, when the fungus grows upon the leaves and stems of the 

 host it not only reduces the amount of the food supply but it often 

 prevents assimilation or the formation of a new supply, thus reduc- 

 ing the vitality of the plant affected. 



It is quite probable that the intensive culture practiced at the 

 present may have weakened the constitution of many of our fruits 

 and vegetables, rendering them less able to resist the attack. The 

 tendency of modern methods is to cause plants to va'-y in certain 

 directions most valuable to man rather than to retain those charac- 

 teristics best for the life and health of the plant. If, then, man 

 would use to the best advantage this tendency to vary in certain 

 directions, he must provide the best environment, and must so far 

 as possible, prevent the attacks of insect and fungous enemies. 



I have said we must if possible prevent attacks of fungous eue- 

 mies, for cure is usually out of the question. The fact that the 



