188 



STATE BOARD OF AGRICULTURE 



CABBAGK-WORMS. 



(Picris olcracra. Picris rapa. and Poiitia iirotodicc.) 



All three of the cabbage butterllies were present at Chathain. We have in this 

 country three ditlcrent species or kinds of cabbage butterliies: two are native and 

 one is introduced from Europe. Of the native species, one Picri.i olrracra, is pure white, 

 the spring lirood having the veins marked with grey scales on the under side of the 

 wings. This is the native form originally found in the northern part of the United 

 States. 'J'he larva feeds on a variety of ]dants, though it takes quite readily to 

 cabbage. The species is now comparatively rare in most places, though quite common 

 at Chatham. 



The southern native species (Pontia protodicc) is white, with a number of black 

 checkered marks on the wings, the female having much more of the black than the 

 male. The larva of this butterfly feeds on cabbage, rape, and a numl)er of other plants. 



'(Pieris olcracca, Pieris ruixc, and Pontia inotodicc.) 



The worst of all three, however, is the imported cabbage-butterfly (Pieris rap(r). 

 This is white, with the tips of the front wings black. The female has two black 

 spots on the front wings; in the male there is only one. Of all the butterflies that 

 are injurious to crops in America this is undoubtedly the worst. The larvoi work in 

 cabbage, rape, rutabagas and various other plants. From the nature of the case, 

 ))oison cannot safely be used, and we have to resort to other means for destroying 

 them. One of these is hot water. This has proven successful in certain cases, though 

 complaints have come from some parties who have used it. The efficacy of hot 

 water depends upon the fact that it takes a less degree of heat to kill cabbage-worms 

 than it does to injure the cabbage. 



The ordinary manner of a}ii)lying the hot water is through a sprinkler. Water is 

 taken, boiling hot, to the field and poured into a sprinkler. From this it is poured 

 on the infested plants, killing the worms, but not injuring the cabbages. Xow the 

 exact distance that must be maintained between the watering-pot and the plants 

 cannot be stated, because the watering pots vary so much as to the size of the holes, 

 and the ttmperature is likely to vary with the distance from the heating apparatus. 

 The finer the holes, of course, the nearer one can get to the plants. If. on the other 

 hand, the holes in the sprinkler are coarse, the drops of water will not cool sufficiently 

 and the plants will be injured. Everyone must try for himself on a few plants at first, 

 and then wait to see the effect. 



Another remedy that is on some accounts better is kerosene emulsion applied in the 

 ordinary way. Professor Hillman, of the Nevada Experiment Station, highly recom- 

 mends the addition of one ounce of Pj^rethrum or Persian insect-powder to the liquid 

 "when it is ready to apply. The writer has tried an emulsion of the kerosene extract of 

 Pyrethrum, wliich amounts to the same thing, and found it very elTective against 

 many resistant insects. 



The work against the early broods of these insects in spring and early summer 

 should be prosecuted with ' great vigor. At this time, before the head begins to 

 form, the most effective work can be done. 



