ol2 Agricultural Experiment Station, Ithaca, N. Y. 



of treatment recommended for the destruction ol" the fungus are 

 generally very effective in controlling the disease. 



B. TREATMENT OF FUNGOUS DISEASES. 



1. Potato Rot or Late Blight. — Bordeaux mixture is the 

 sovereign remedy for the rot or late blight. It was first success- 

 fully used by the French in 1886 and since that time innumerable 

 experiments have been made with this fungicide in checking the 

 trouble. Success has followed whenever the applications have been 

 properly made, and it is no longer a question whether the mixture 

 will prevent the blight ; it is now entirely a matter of judgment 

 and skill on the part of the grower. If the Bordeaux mixture is 

 properly made*, and thoroughly applied at the right time, scarcely 

 a decayed tuber should appear in the held. It is impossible to state 

 when tlie first applications should be made, nor how many times the 

 plants should be treated, for the conditions vary so umch in differ- 

 ent localities. As a rule it is unnecessary to begin spraying before 

 the middle of July, and the tirst of August will prove none too 

 late in the majority of cases. The character of the season, and the 

 prevalence of the disease in former years must serve as guides as to 

 the best time to begin spraying. In certain localities the late blight 

 appears with considerable regularity, and in such cases it is well to 

 spray about ten days before the period in which the trouble is 

 generally first noticed. 



Later applications may be made at intervals of one to three 

 weeks, depending upon the weather. Even in years favorable to 

 blight, three applications should be sufiicient to protect the plants 

 almost perfectly. The foliage should be thoroughly covered from 

 above, and if the spray may be conveniently applied from below 

 also, so much the better. A fine and abundant spray will be found 

 most satisfactory (see page 325 for report upon spraying machinery). 



2. Early Blight. The successful treatment of the early blight 

 is by no means an easy matter, as appeared in the discussion of its 

 probable causes. It was shown that the early blight does not appear 



* A fjood mixture for use npon potatoes iiiiiy be prepared by dissolving six 

 pouuds copper sulphate iu about twelve gallons of water; slake four pounds 

 quirklinie and add fo the copjjer snl])liate sohilion. Dilute to forty gallons. If 

 the ferocyanide of potassium tost is employed, put -in about one-fourth more 

 lime than the test solution shows to be necessary. 



