INJURIOUS TO CABBAGE AND RELATED CROPS 25 



tected in the curled leaves where it is difficult to hit them with 

 a spray ; their bodies are covered with a white waxy bloom so 

 that the spray does not readily wet them ; and they occur in 

 dense masses or colonies, 

 and considerable force is 

 required in order to reach 

 those beneath the others. 

 Under commercial condi- 

 tions, it is not possible to 

 destroy all the lice by 

 spraying. The best that 

 can be expected is so to 

 reduce their numbers that 

 the plant will be able to 

 continue its growth and 

 develop the head. Efficient 

 work can be done by spray- 

 ing with the so-called 

 whale-oil or fish-oil soap, 

 10 pounds in 100 gallons 

 of water, or with "Black 

 Leaf 40" tobacco extract, 

 I pint in 100 gallons of 

 water with 4 or 5 pounds 

 of soap added. The first 

 application should be made 

 as soon as the lice begin to 

 cluster on the young plants. 

 At least 100 gallons should 

 be applied to each acre 



when the plants are young. The most eff'ective and economical 

 method of application is to use an ordinary potato sprayer 

 (Fig. 24) equipped with a Y to which are attached two leads 

 of hose 10 or 12 feet in length. At the end of each hose is an 



Fig. 23. — A radish seed-stalk infested 

 by the cabbage aphis (enlarged). 



