212 



AGRICULTURE ON THE PACIFIC SLOPE 



Plum aphis. In some seasons plum trees are overrun and 

 their leaves are considerably injured by the bluish green 

 plum aphis. It is easily controlled by spraying. 



Cabbage aphis. This sometimes injures young plants 

 seriously, and later infests the cabbage heads, making them 

 unpleasant to handle. It is also found on wild mustard and 

 wild radish; these weeds should therefore be kept down as 

 much as possible. Sometimes it destroys the crop of mustard 

 seed. 



Plants may be sprayed in the seed bed and dijp_2edjjitoa 



soap or kerosene mix- 

 ture, just before set- 

 ting them out in the 

 field. Plants may be 

 sprayed in the field 

 with petroleum dis- 

 tillate, about half as 

 strong as for scale 

 insects. (New Mex- 

 ico Experiment Sta- 

 tion, Bulletin 68; 

 Utah, 65.) 



Melon aphis. This 

 breeds on pepper 

 cress and alfalfa. 

 Near melon fields 

 alfalfa should be 

 cropped close, and 

 pepper cress should 

 Station, bulletin 47; 



FIG. 122. At the left an apple branch at- 

 tacked by aphis. It bears smaller apples 

 and more of them. Ordinary branch at 

 the right. 



be destroyed. (Arizona Experiment 

 New Mexico, 63, 68.) 



Apple-leaf aphis. There are two kinds of aphisjon the 

 apple le 



' one of which causes what is known as " little 



