378 



GENERAL SCIENCE 



controlled by treating the "seed" potatoes with formalin 

 solution before planting, and by rotation of crops. 



Potato blight attacks the leaves of the potatoes and 

 causes them to die. It can be prevented by keeping the 

 potatoes covered with Bordeaux mixture to prevent the 

 entrance of the fungus spores. About five sprayings 



are necessary, but 

 one or two more 

 are sometimes 

 given. 



262. Insect Pests. 

 -The animal pests 

 which injure culti- 

 vated plants are 

 mostly insects. The 

 San Jose scale, 

 which is a sucking 

 insect, reproduces 

 very rapidly and is 

 very destructive to 

 both peach and 

 apple trees. It can 

 be killed by spray- 

 ing with strong lime-sulphur solution when the leaves 

 are off of the trees. Spray that is strong enough to kill 

 the scale will also kill the leaves. 



The codling moth, a small insect, is very destructive 

 to apples and pears. The adult moth deposits its eggs on 

 the young apple just after blossoming. The egg hatches 

 and the larva crawls to the blossom end of the apple and 

 eats its way into it. The apples thus attacked usually 

 fall when they are about the size of thimbles. About this 

 same time the worm or larva reaches its growth and 



STAGES OF THE CODLING MOTH 

 (a) the moth or adult insect, slightly en- 

 larged; (b) the egg, greatly enlarged; (c) the 

 full-grown larva, slightly enlarged; (d) the 

 pupa, slightly enlarged; (e) the pupa in its 

 cocoon on the inner surface of a piece of bark, 

 reduced about one-half; (/) moth on bark and 

 empty pupa skin from which it emerged, about 

 natural size. 



