Orchard Pests and their Control 361 



iar reddish cast. Many trees die in midseason, with fruit and 

 foliage clinging, the second season after symptoms of trouble 

 were noticed. The inner wood of the branches of some of the 

 affected trees is dark-colored, or black-hearted, a condition which 

 has popularly been supposed to result from injury by frost alone. 

 Another symptom which seems to be associated with this trouble 

 is the splitting of the bark on the trunks. Such wounds bleed 

 profusely, and it may be that some of the excessive bleeding 

 which sometimes takes place from wounds made in pruning may 

 be due to the same cause. In all cases the starting point is either 

 at or below the surface of the ground. Fungi may be responsible 

 for some of the dead trees, but this has never been definitely 

 determined. The common pear-blight may also work in the 

 roots of apple and pear trees, but this is unusual. 



The authors have spent much time over this all too common 

 disease, but they were unable to arrive at any conclusions. For- 

 tunately, our co-worker, Dr. W. P. Headden, became interested 

 in the subject, and in a recent bulletin he gives the results of his 

 investigations. 1 He found upon analysis that the inner bark and 

 wood of affected trees, not dead trees, contained a large percent- 

 age of arsenic, as much as 12.77 parts in a million. All fruit- 

 growers know that even a small amount of soluble arsenic in the 

 soil is fatal to vegetation, but they have felt safe in using large 

 quantities of the various arsenical sprays for the reason that 

 these forms of arsenic were supposed to be insoluble. It has 

 been the custom in some sections to spray from six to twelve times 

 a season for the codlin-moth. The appliances were often crude 

 in form, consequently much spray material was wasted and was 

 deposited on the ground. Naturally, the greatest accumulation 

 is around the base of the tree where the injury occurs. Analysis 

 of soil taken from near the base of trees, to the depth of one 

 foot, shows that arsenic has accumulated in varying amounts up 

 to 61.3 parts of arsenic acid in a million of soil. 



Even such large amounts of arsenic would be harmless if it 

 remained insoluble, as had been supposed. Dr. Headden finds, 



1 Headden, W. P., "Arsenical Poisoning of Fruit Trees," Colorado 

 Expt. Sta. Bui. 131, 1908. 



