Black Knot of Plums and Chhrkies. 649 



19 and 29. The conclusion reached was that " the number of 

 wans was very decidedly less where treated with the copptr mix- 

 ture, than where untreated * ^ * and we believe that the 

 plum wart may be held in check by this remedy." 



In the spring of 1893 some experiments were begun with the 

 intention of carrying on the work at least two seasons. A thicket 

 of Morello cherry trees and sprouts was chosen for one field of 

 operations. The plants were well covered with knots at the time, 

 and these were all allowed to remain until the following year. 

 The piece was divided into two nearly equal parts by cutting out 

 the brush across a convenient portion of the strip. One part was 

 treated and the other was not. The only fungicide used was the 

 Bordeaux mixture. This was applied in 1893 upon the following 

 days: March 29, April 18, May 6 and 30, and June 13. The 

 trees were as well covered as could be done, but some of the parts 

 were difficult of access. 



The work was continued in 1894, and after one application had 

 been made all the knots were cut out. This was done April 25, 

 and the knots from each portion were counted so that the relative 

 number of branches in each portion could be estimated and a basis 

 for comparison might be made when the knots should again be 

 cut. They had been allowed to remain on the tree during the 

 preceding year .so that the chances for further infection should be 

 as favorable as possible. At the time of their removal no marked 

 difference could be seen in favor of either portion as regards the 

 relative abundance of the knots, although on the sprayed portion 

 they may not have been quite so thick. 



The Bordeaux mixture was again used in 1894. It was applied 

 to the same portion treated in 1893 and upon the following dates : 

 April 9 and 25, May 21, June 6 and 27, July 10 and 20, and Aug- 

 ust I . This number of treatments gave the limbs and foliage a 

 blue color which they retained until the leaves fell to the ground, 

 and at this writing, December 3, the branches still show a decided 

 coloration. 



Figure 5 represents the thicket as it appeared November 26 be- 

 fore the knots were cut out after the summer's growth. The illus- 

 tration does not represent plainly the number of knots present, 

 but it will be noticed that there are many more on the unsprayed 



