INJURIOUS INSECTS. 109 



bugs will not injure the cabbage as long as there are 

 mustard or radish tops for them to eat. 



THE CABBAGE APHIS. 



Next to the imported cabbage worm, this spe- 

 cies is perhaps the most injurious insect enemy of 

 the cabbage. Nearly as many remedies have been 

 recommended for this pest as for the European cab- 

 bage worm. It should be remembered that plant 

 lice are only killed by insecticides which smother or 

 kill by contact. None of the poisons will kill them. 

 The best remedy for outdoor purposes is kerosene 

 emulsion diluted with ten parts water. It should 

 be applied to the lower as well as the upper sides of 

 the leaves, and, if possible, while the cabbage are 

 small. In a number of tests of Pyrethrum, or 

 Buhach, Persian insect powder and tobacco dust, 

 tobacco was found to be the most active killing 

 agent. Pyrethrum and Persian insect powder are 

 considered good, but are liable to be adulterated and 

 to lose their strength. 



