New York Agricultural Experiment Station. 395 



making the applications. The results of the treatment with 

 Bordeaux mixture, according to the plan previously explained, 

 throw some light on these questions. 



It will be remembered that three series of treatments were 

 made. In Series 1 the first spraying was given May 17, when 

 the buds were breaking; the second was given just after the trees 

 had gone out of blossom; the third was given June 1. In Series 

 2 the first spraying was made May 17, the second was made 

 June 1 and the third was made June 15. In Series 3 the first 

 treatment was made June 15, the second was made July 16. 

 The estimate of the amount of loss or injury to the foliage from 

 all causes, which was made September 28, gave the following 

 results: 



Series 1. Treated May 1, ^ Bordeaux mixtuie 24 per cent, injury or loss 



May 17 and JuueJ. ( No treatment 95 per cent, injury or loss 



Series 2. Treated May 17, j Bordeaux mixture 10 per cent, injurv or loss 



- - ) No 



June 1 and June 15. \ No treatment 78 per cent, injury or loss 



jries 3. Treated June 15 5 Bordeaux mixture 41 per cent, injury or loss 



and July 16. ( No treatment 96 per cent, injury or Iobs 



Judging from these results it is not best to make the first treat- 

 ment later than the first of June. Arthur* has shown that the 

 leaf-spot fungus lives over winter in the infested leaves, and that 

 the spores of the mature form of the fungus begin to ripen about 

 the first of June. In the above experiments the best results 

 were secured when the foliage was covered with Bordeaux mix- 

 ture before the time when these spores are said to ripen, that 

 is to say, before June 1. This confirms tTie results secured by 

 Thaxter. f 



• Arthur, J. C. Plum Leaf Fungus. Kep. N. T. State Exp. Sta. 1887. 6: 347-3.50. f. 2. 



f Thaxter, Roland. Rep. Conn. Sta. 1889: 176. 1890: 102. 



Dr. Thaxter reijorts an experiment in 1889 in which two Lombard trees were sprayed with 

 Bordeaux mixture, \-^% formula, May 22, June 14 and July 16. A third tree wa.s left unsprayed 

 for comparison. The two sprayed trees held their foliage intact up to severe frost in October, 

 showed hardly any black-knot and matured a fair amount of fruit. The untreated tree was 

 leafless in A uj;ii8t, matured no fruit and was badly infested with black-knot '-The mixturs 

 did not adhere to the fruit to any extent, which may account for the fact that the fruit rot was 

 not more eflfectually controlled." 



In 1890 similar ai)plication was made to several large plum trees, thereby presfrving their 

 foliage intact. In another place Bordeaux mixture was api)lied to plums and cherries with simi- 

 lar results while a lew untreated trees lost their foliage in July. 



