INSECTS INJURIOUS TO CABBAGE, ETC. 325 



Control. As the chrysalids pass the winter on the old stumps, 

 foliage, and rubbish on the field, it is evident that they should be 

 destroyed and the field plowed as soon after the crop is removed 

 as possible. A few stalks may well be left standing here and 

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

 worms from eggs laid by late female 



The most effective means of control is spraying or dusting 

 with Paris green or arsenate of lead. The former is used J 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. 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 



FIG. 274. The southern cabbage butterfly; a, male; 6, female. (After Riley.) 



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 



