12 
The Colorado Experiment Station. 
a good recovery. The winter of 1905-06 was less severe and the 
fruit buds passed the winter safely. While the growers thinned 
their peaches as carefully as usual, the trees, having failed to fully 
recover from the severe freeze in one growing season, were un¬ 
able to mature the normal crop. Where severely pruned, the 
trees matured their crop well. Following severe freezes which 
injure the wood, it would be well to thin the first crop more closely. 
COPPER SULPHATE INJURY. 
Copper sulphate has been placed about trees with injurious 
results by some orchard men. When taken up by the roots the 
material blasts the foliage and causes it to fall. The most tell¬ 
tale effect is a blackening of the outer ring of the sap wood and 
cambium. When taken up by the roots in a concentrated form, the 
wood and bark near the base of the tree are killed in strips of 
varying width. Nearer the top where the material spreads more, 
the tendency is for the leaves to drop, and later a new growth starts. 
The upper limbs probably recover. The strips of bark on the trunk 
and limbs, however, seem to be perfectly dead. 
The stock solution used in spraying with arsenite of lime, 
prepared b}^ dissolving white arsenic in water and sal soda, is very 
destructive to plant life. The general practice of keeping this 
solution in the orchard under a tree should be discouraged. If a 
small amount is spilled, or if the vessel leaks, the material will 
soon kill the tree. In fact, it almost appears as though in some cases 
the material will kill peach trees when placed under them in an open 
vessel. The fumes given off when boiling this solution will kill 
trees without a doubt, and this boiling should be done some distance 
from the orchard. I have seen trees standing twenty feet from an 
open packing house door killed on the side next to the packing 
house in which the material was boiled. 
Some Ben Davis and Gano orchards have shown a very 
sickly yellow color during the summer, and investigations have 
shown that the trees were suffering from arsenical poisoning. The 
trees were sprayed with arsenite of lime in which the quantity of 
lime used was deficient, or with an arsenate of lead which contain¬ 
ed a large amount of free arsenic. The growth of foliage is scant 
and the color yellow. Though the material may have been used 
only once, the effect seemed to last through the season. There 
seems no reason to believe but that the trees will recover the coming 
season. 
THINNING APPLES. 
Experiments were undertaken in thinning apples during the 
eaily part of the season. An orchard was selected in which large 
