170 



STATE BOARD OP AGRICULTURE. 



Neither rape nor cauliflower suggest themselves as fit subjects for the 

 arsenites. Hot water has been used extensively for killing the worms. 

 The water is poured onto the plants through a sprinkler, held at just 



the right distance from the 

 plant, the distance to be de- 

 termined by experiment. It 

 is jjossible to kill the worms 

 without injuring the plants, 

 when once the proper dis- 

 tance has been determined, 

 depending upon the size of 

 the holes in the sprinkler 

 and the temperature of the 

 water. However, the sprink- 

 ler method becomes very 

 burdensome when used on a 

 large scale. The use of 

 Pyrethrum or of Pyrethro- 

 kerosene emulsion is even 

 more effectual and involves 

 less labor. Pryethrum or 

 Buhach if fresh and pure 

 can be made to do all the 

 work with very little labor. 

 Apply with an atomizer, us- 

 ing one-half ounce to a gal- 

 lon of water. We have used 

 this with very gratifying re- 

 sults apparently killing all 

 the worms that were hit. It 

 is but fair to state, however, 

 that the Pyrethrum used 

 has been of the very highest 

 quality, being that grown in California and kept in tightly sealed tin 

 cans. This costs about 75 cents per pound, making the spray 2^/2 

 cents per gallon. A gallon will spray a large number of plants, so 

 that after all it is not expensive. 



Whale-oil Pyrethro-kerosene-emulsion, or emulsion to which Pyreth- 

 rum has been added (see directions for making insecticides) works very 

 nicely, in fact nearly as well as the Pyrethrum alone and it costs only 

 a little over a cent per gallon, if the materials are purchased in fairly 

 large quantities. In fact if one can not procure the best of Pyrethrum 

 to begin with, it is likely that the emulsion referred to will prove more 

 uniformly successful. Dilute the emulsion about eight times with 

 water. When diluted ten times, it failed to kill a few of the worms and 

 when diluted only six times, it burned the foliage slightly. 



The Cabbage-looper {Plusia hrassicae). 



Less conspicuous in its work, but nevertheless of much importance, 

 is the cabbage-looper, so named because of the looping or measuring gait 

 of the larva. Tliis pale-green, almost translucent larva reaches a size 

 slightly larger than the common ''cabbage-worm." It is rather obscurely 



Fig. 18. — Imported cabbage-worm larva pupae and 

 adult, slightly enlarged. Original. 



