174 



FUNGI AND FUNGICIDES 



tial, as diseased seed will give diseased sprouts, which, 

 in turn, will grow a crop of worthless potatoes. 



2. The selection of healthy sprouts is plainly nec- 

 essary, in case the fungus gets into the hotbeds, and 

 under no circumstances should diseased plants be put 

 into the field. The test of using copper fungicides in 

 the hotbed has not been made, but, from analogy, seems 

 to promise assistance. If the fungicide is used the 

 shoots should be kept green with it until pulled. 



3. Fields which have become so impregnated by 

 the disease that they refuse to grow profitable crops, had 

 best be added to the regular farm rotation. This 

 method will, if continued for several years, allow the 

 accumulated infective material to burn itself out by con- 

 suming all available food material in the soil. 



4. Decaying roots and the refuse after digging 

 should be carefully removed from the field and burned, 

 as such debris adds to the food of the parasite. 



5. The use of large quantities of barnyard manure 

 probably favors the development of the trouble, since it 

 adds greatly to the decaying vegetable matter of the soil. 

 Where the use of commercial fertilizers can be made to 

 take the place of manure, it will certainly be desirable 

 to make the change. 



6. Although no experiments have yet been com- 

 pleted upon the matter, it is probable the spread of the 

 disease in the bin may be checked by dipping the roots 

 in one of the copper mixtures, preferably the ammoni- 

 acal solution, before storing for the winter. What effect 

 tobacco smoke, or the fumes of sulphur, would have in 

 checking the disease in the bins remains to be ascertained. 



Literature. The two most important articles con- 

 cerning this disease that have come to the writer's notice 

 are, first, one by Dr. Halsted, published in 1890, in Bul- 

 letin 7G of the New Jersey Experiment Station (pp. 

 7-14) ; and, second, one by Dr. Halsted and Mr. D. G. 



