278 STATE BOARD OF AGRICULTURE. 



tlie trees after they have been pruned and with good care they will 

 I)erhaps be in even better condition than before they were attacked. One 

 should not expect the best results from this treatment upon old trees, 

 O!" after they have been seriously injured. 



THE PROPAGATION OF THE SCALE. 



Unlike most other scale insects the San Jose scale brings forth its 

 young alive. About the middle of June, in this latitude, the young scales 

 will begin to appear from beneath the covering of the old females. A 

 single scale will often develop four or five hundred. At first, the young 

 are so small that they can barely be distinguished by the unaided eye. 

 They are yellow, oval in form and can move about to some extent by 

 means of six poorly developed legs. For a few hours, or perhaps days in 

 some cases, they crawl along the branches until they find what seems a 

 suitable place, when they insert their long thread-like beak into the bark 

 and begin their transformation, after which time they do not move from 

 this place. In a short time the young scale takes on a circular form and 

 begins to secrete a shell. At first it has a creamlike color but it soon 

 turns dark brown or black. 



In seven or eight weeks, or about the middle of August, the second 

 brood will appear and develop exactly the same as the first, and a third 

 and perhaps a fourth brood will appear later in the season. As the 

 different females will not breed at exactly the same periods it will be 

 possible to find crawling larvae upon the trees at almost any time from 

 the middle of June until the weather becomes quite cold. The partially 

 developed insects are generally killed by the winter, but, if one per cent 

 winter over, the trees will by the middle of June be as badly infested as 

 they were in the fall. It can be readily seen that if each female scale 

 develops 400 young, one-half of which are females and that all of these 

 breed and if this is continued until four broods have been produced, 

 the progeny from a single female scale in one season will amount to 

 more than three billions. Even though but two females- from each brood 

 live and breed the increase will in a single season be a hundred fold. 



HOW IT IS DISTRIBUTED. 



As the female scales at no time have wings, it is a question as to how 

 they spread from tree to tree and from orchard to orchard, as it is known 

 tliat their legs could at most carry them but a few feet and over a com- 

 paratively smooth surface. It is supposed that, while crawling, the 

 larvae might get upon the legs of other insects and even of birds and 

 thus spread over large areas. It is also quite sure that the wind serves 

 lo spread them to considerable distances and in large numbers. 



For a number of years after its introduction into the eastern states, 

 \N'here it first appeared in some of the large nurseries, it was distributed 

 broadcast upon nursery stock. The laws of nearly all of the states now 

 require the inspecting of nursery stock before it is dug, and if nny 

 trees are found to be infested they are destroyed and all other trees that 

 are subject to attack that have grown within a half mile must be fumi- 

 gated with hydrocyanic acid gas at a strength that has been found fatal 

 to the scale and yet which will not injure the trees. 



