428 F. M. Rolfs 



In preparing to set out an orchard, great care should be used in 

 ordering the trees. Purchases should be made only from reliable nursery- 

 men, and, if possible, the nursery should be visited and the trees inspected 

 in the fall, while they are still in full leaf, in order to make sure that the 

 foliage is free from shot-hole condition and the twigs are free from cankers. 

 If this is impossible, the trees should he carefully examined for black 

 cankers in the spring, before they are set out. The disease is usually 

 more easily detected in fall than in spring. All infected trees should be 

 rejected. 



Since the organism is readily carried from one tree to another, the lo- 

 cation of a young orchard or nursery in relation to old, diseased trees or 

 orchards is of considerable importance. The writer has frequently ob- 

 served old orchards which served as centers of inoculum for young trees. 



In 190(3 a tract of one hundred and sixty acres of new land near Koshko- 

 nong, Missouri, which bordered an old peach orchard on the south, was set 

 with two-years-old Elberta peach trees. During the first year the foliage on 

 the trees in the first fifteen rows became more or less diseased, but during 

 the second year the disease advanced more rapidly and the foliage on (ices 

 in the two hundred and fifty rows next to the old orchard became invoked. 

 The trees beyond this, however, were norma! and were making satisfac- 

 tory growth. At the end of the third year nearly every tree in the entire 

 orchard was diseased. Those in the first fifty rows bordering the old 

 orchard contained more twig cankers than did those in any other part. 



ERADICATION 



After the disease has once become established, the chief point of attack 

 is, of course, the cankers on twigs, limbs, and trunks of the trees, since 

 these wounds not only serve to carry the organism through the winter 

 but also in many cases tide it over unfavorable periods in summer. ( !are- 

 ful pruning not only removes many of the twig cankers — and very often 

 the cankers near the tips of the twigs contain the greatest numbers of 

 bacteria — but also serves to stimulate new growth which often 

 shows considerable resistance to the attacks of the organism. It is 

 of course impossible to remove all the twig cankers in a crop season. 

 But in an off year, when the fruit buds have all been winterkilled, the 

 twig cankers on the old trees can be removed by cutting back the limbs 

 to one-fourth of their entire length and carefully trimming out all the 



