236 AGRICULTURAL EXPERIMENT STATION. [Jan. 



poorly nourished plants suffer the attacks of parasites of all 

 sorts, and have no power to resist them. Secondly, where 

 a crop has suffered from a fungous disease in one season and 

 a good crop of the same kind is desired in the following 

 season, every tangible trace of the disease must be removed. 

 For example, if a vineyard has suffered from mildew or black 

 rot, all diseased leaves and berries should be collected at 

 the end of the season with scrupulous care and wholly 

 burned ; and the same advice applies to a large list of cases. 

 Thus incalculable numbers of the spores of the fungi of the 

 respective diseases will be prevented from infesting the next 

 season's crop. In some cases where the spores remain in 

 the soil, as in the stump foot of cabbages or the smut of 

 onions, the attacks of the disease can only be avoided by 

 rotation with crops upon which the fungus in question can- 

 not live. Thirdly, wild plants, which, being nearly related 

 to a given cultivated one, may be subject to the same dis- 

 ease, or which bear a complementary spore form of a 

 pleomorphic fungus, should be carefully excluded from the 

 neighborhood of cultivated ones. Thus, wild cherries or 

 plums, which are equally subject to the black knot, should 

 be kept away from plum orchards ; and spinach fields should 

 be kept free of pig- weed, since both plants are attacked by 

 the same mildew; and again, since red cedars bear one 

 spore-form of a fungus whose other form is the rust of apple 

 leaves, it is plain that they should not be allowed to grow 

 near an apple orchard. 



The importance of these preventives is often underrated 

 by persons who understand and use successfully other forms 

 of treatment. It is evident, however, that, in removing as 

 completely as is possible the conditions which favor the 

 abundance and increase of a fungus in the vicinity of its 

 host plant, half the battle is won. When this has been 

 done, we may protect the plants by the external application 

 of fungicides. 



These preparations, when properly prepared and when 

 applied at the right times and in the right way, have been 

 abundantly proved to be of the greatest value, and often to 

 determine the difference between a full crop from plants on 

 which they are used and practically no crop where they are 

 not applied. 



