234 INSECTS AFFECTING TRUCK CROPS 



before many of them have laid their eggs. Two different recipes 

 for this poison spray are as follows: 



(a) 3 ounces arsenate of lead, 2^ pounds brown sugar, 4 gallons water. 

 (6) 1/5 ounce arsenite of soda, ^ pint cheap molasses, 1 gallon water. 



It is not necessary to spray all the plants in a field. If an occa- 

 sional row is treated, sufficient attraction is offered. Late planted 

 cabbages are not so seriously affected as are early cabbages : Hol- 

 land cabbage appears to be exempt. Applications to the roots are 

 rarely very effective. 



The Cabbage Aphis or Cabbage Louse. On the under side 

 of the leaves of cabbage and other members of the mustard family 



: 



FIG. 243. Tarred paper disks applied to plants: a, correctly applied; 6, incorrectly. 



are frequently found, in summer, large colonies of these lice (Aphis 

 brassicce Linn.). They are yellowish. Winged individuals appear 

 from time to time and fly from one plant to another. The average 

 length of life of each generation is about twelve days, and each 

 wingless female gives birth to about forty young. In the fall 

 winged males and females appear which mate and thus produce 

 eggs for the next season's generations. 



Injury. Plants are weakened by a constant drain upon the 

 sap and are thus made unfit for use, even if they reach a market- 

 able age. 



Control. Practice clean cultivation and the destruction of all 

 refuse of the year's crop in the fall. The curling of leaves protects 

 the lice and prevents successful spraying, for any spray used must 



