108 FRUIT-GROWING 



gives them their common name of scale insects. 

 The shape of the scale varies with different 

 species and different genera, but in the case of 

 the San Jose scale it is round and marked with 

 concentric circles about a raised center. The 

 male scale of this species varies from the fe- 

 male in being somewhat elongated and very- 

 much smaller. It is chiefly the females, usually 

 fertilized in the fall, which carry the genera- 

 tion over the winter and these may be observed 

 throughout the season closely adhering to the 

 twigs, often sheltered in cracks or in the pro- 

 tecting spaces at the base of the bud. 



The insects themselves are tender, "juicy" 

 mites easily killed by contact insecticides, but 

 the fact that they are protected by their hard 

 covering gives them immunity against all ex- 

 cept the most drastic sprays that we can use. 

 Consequently our work against insects of this 

 class must be done in the winter season when 

 the tree is devoid of foliage. To use an effi- 

 cient material against the San Jose scale in the 

 summer would mean that we would ruin the 

 foliage on the tree. The presence of the foli- 

 age, too, would render it almost impossible to 

 do effective work as every part of the tree — the 

 trunk, the branches and every twig — must be 

 thoroughly soaked with the spray material if 

 we are to expect one hundred per cent, effi- 

 ciency from our work. 



