INJURIOUS TO CABBAGE AND CRUCIFEROUS CROPS 359 



there and be kept well poisoned, so as to act as traps to destroy 

 worms from eggs laid by late females. 



The most effective means of control is spraying or dusting 

 with Paris green or arsenate of lead. The former is used ^- pound 

 to the barrel and the latter 2 to 3 pounds per barrel of water. 

 As the foliage of cabbage is extremely smooth it will be advisable 

 to add 2 or 3 pounds of resin soap or " sticker " to render the 

 material more adhesive (see page 46). The arsenicals should 

 be applied as soon as the plants are set, and they should be kept 

 well covered until the heads are half formed. If this is done, 

 the young larvae will be destroyed before they burrow into the 

 heads, and there will be but little damage after the spraying is 

 stopped. Although there is some prejudice against poisoning 

 cabbage, it is entirely unfounded, for it has been shown that a 

 person would need to eat twenty-eight cabbages at once, if dusted 

 in the ordinary manner, to secure poisonous effects. It is obvious 

 that plants should not have large quantities of dust placed on 

 them after they commence to head, and such applications are 

 entirely unnecessary. 



Various contact insecticides may be used against the worms 

 on a few plants, but are not practicable for large acreages. Thus 

 water heated to 150 F., will kill all the worms which it hits. 

 Kerosene emulsion will kill the larvae, but must hit them, and 

 may leave an odor on the plant. Pyrethrum or buhach has been 

 used effectively, applying it either dry or diluted with flour, 

 or sprayed as a decoction at the rate of 1 ounce to a gallon of 

 water. Dilute tobacco extract has also proven effective, but 

 all of these substances have the disadvantage that they 

 must be brought into actual contact with the worms to kill 

 them. 



