226 MONTANA EXPERIMENT STATION. 



depositing their eggs late in June, and early in July. In about three 

 weeks^the eggs hatch and the young larvae bore under the bark, 

 where they feed for three years, first just vmder the bark and later 

 in the woody parts of the stem. On young trees they most common- 

 ly occur at about the surface of the ground as shown in the photo- 

 graph above referred to. The location of the burrow may often be 

 detected from the outside by the discoloration or slightly sunken 

 condition of the bark. 



At the end of three years from the time the egg was deposited 

 the beetle bores out from the pupal chamber which it constructed 

 at the end of its larval life. The sexes mate and the eggs are de- 

 posited for the new generation. 



NATURAL ENEMIES. 



The downy wood-pecker which is so common in Montana and 

 which is so often seen in our orchards, is the fruit-grower's friend. 

 Besides picking up miscellaneous pests it locates burrows of this 

 borer and extracts them in considerable numbers. In the older 

 orchards of Montana scarcely a tree can be found that does not bear 

 the marks of wood-peckers, a large proportion of which are made by 

 this species. 



METHODS OF CONTROL. 



Borers as a class of pests are difficult to control. When once 

 in a tree they cannot be reached with an insecticide. They may in 

 many cases be removed by means of a sharp knife and a wire but 

 their presence is not usually detected until a large part of the dam- 

 age has been accomplished, and the injury done to the tree in re- 

 moving the larvae may be greater than would be done if they 

 were left to do their worst. It has been found, therefore, that clean, 

 strong, cultural methods and the use of deterrent application on the 

 trees, both of which are preventatives, constitute the best means of 

 control. 



In the first place, in planting out a young orchard the trees 

 should not be allowed to become weakened and so rendered liable 

 to attack. Young trees in an exposed position should be protected 

 against the strong rays of the winter's sun. The alternate thawing 

 and freezing on the exposed side of the trunk produces the condition 



