A Bacterial Disease of Stone Fruits 429 



one- and two-years-old twigs from the center of the trees. Lesions on the 

 limbs and trunks soon form rough, open cankers and can easily he found. 

 Such wounds must also be cut out, or, if this is impossible, the diseased 

 tissue must be completely removed by cutting around the canker well 

 into the healthy part of the limb or the trunk. In every case the wound 

 should be thoroughly disinfected with corrosive sublimate solution, one 

 part to one thousand parts of water. The organism can usually be elim- 

 inated in this way on the apricot, the nectarine, and the peach. In the 

 case of the plum, however, especially on the Japanese varieties where the 

 organism has invaded the large limbs and the trunk, it is practically im- 

 possible to save the tree. 



In 1907 the peach trees in the Missouri State Fruit Experiment Station 

 variety orchard were heavily pruned. All the limbs were cut back one- 

 fourth of their length. One hundred and thirty Elberta trees of the 

 same age were not severely pruned but were treated in every other way as 

 the other trees. During the fall the foliage on the pruned trees was of a 

 better color and more nearly free from disease than that on the unpruned 

 trees. In 1908 little or no injury was observed on the pruned trees, while 

 foliage on all unpruned Elberta trees was more or less diseased. Twenty 

 per cent of the leaves finally fell, and twig cankers also were plentiful. 

 Chandler, 4 of the University of Missouri, has also observed in his work 

 that severe pruning tends to make the trees more nearly free from the shot- 

 hole disease. 



PROTECTION 



Spraying 



Since bordeaux mixture has been used successfully in controlling various 

 plant diseases, and lime-sulfur has been used also with more or less suc- 

 cess, a number of experiments were undertaken in order to determine 

 the effectiveness of these mixtures in controlling this organism. 



In L908, thirty-two eight-years-old Elberta peach trees were sprayed 

 seven times with bordeaux mixture, and twelve were used as checks. 

 The firsl application was made with the 6-4-50 formula on March 12, just 

 before the fruit buds opened. The other six applications were made with 

 the 2-9-50 formula after the leaves had unfolded; the first, of these was made 

 on April 21, and the others followed at intervals of from twelve to fifteen 



1 Chandler, W. II., in a letter dated September 26, 1912 



