INSECTS INJURIOUS TO ORCHARD TREES 447 



begin active feeding. Soon after this they begin the secre- 

 tion of the waxy substance which is to form their scaly 

 covering. Their development is very rapid and after about 

 thirty days they themselves begin to produce living young. 

 Thus there may occur from two to six generations during the 

 summer. 



There are several kinds of parasites that are of more or less 

 importance in controlling the San Jose scale, but none of these 

 acts quickly enough to make it unnecessary to use active meas- 

 ures in fighting the pest. Many kinds of sprays have been 

 tried, but the sulphur-lime spray is the one which is now most 

 generally used. The directions for making and using this spray 

 will be found on page 416. Before spraying, the trees should 

 be pruned back as much as is practicable so that all of the 

 remaining wood may be thoroughly covered. In some re- 

 gions miscible oils are extensively used. 



There are four or five other species of scale-insects that look 

 very much like the San Jose scale, and, indeed, can only be 

 distinguished from it by the use of the lens, but as their habits are 

 much the same and as the same remedies are to be used for 

 them they need not be especially discussed. 



Oyster-shell Scale (Lepidosaphes ulmi). As the name in- 

 dicates, the scale of this insect is shaped somewhat like an elon- 

 gate oyster shell. It is long and narrow, usually somewhat 

 curved toward the posterior end. The color varies from light 

 brown to dark brown. This is a very common pest on almost 

 all kinds of fruit trees, occurring also on many other trees both 

 cultivated and wild. As it is large enough to be easily seen 

 it is perhaps better known than almost any other species. It 

 passes the winter in the egg stage, the eggs being well protected 

 by the firm tough scale under which they lie. In many regions 

 only a single brood occurs each year, but in the South there may 

 be two broods. This insect is subject to the attack of several 

 natural enemies, among the most important of which are the 

 chalcid-flies, which sometimes control the pest fairly well. It 

 is very difficult to kill the eggs by spraying in the winter, but 

 if the trees are thoroughly sprayed with the sulphur-lime wash 

 just before the buds open most of the young will be killed soon 



