10 INSECTS AFFECTING VEGETABLE AND TRUCK CROPS. 



be discovered. Undoubtedly also wasps of the genus Polistes, be- 

 sides Lhnnerium luiwa'iiennc Cram., Chelonus hJacK-hunil Cram., and 

 Cremastus hymenite Vier., enemies of H. fascialis in Hawaii, will 

 attack this species in its larval condition. 



CONTROL. 



It is obvious fi-om the notes on the occurrence of this insect that 

 injury was discovered too late for the application of insecticides. In 

 practically every case the larvae were in the last stage, the few younger 

 larva^ merely indicating the exception to the rule. Such being the 

 case it was not possible to test any remedies whatever. It is inter- 

 esting to relate, how'ever, in the case of Swiss chard, that many of the 

 plants, being able to withstand a considerable degree of cold, re- 

 covered and put forth new leaves, practically a second crop of leaves 

 developing, and that the moths hatched from all larvae and did not 

 deposit Qgg'^, at least not in confinement. AVhat they would do under 

 natural conditions is not quite certain for this latitude. 



In the case of the related Hawaiian beet webworm, Mr. H. O. Marsh 

 has demonstrated that Paris green applied at the rate of 2 pounds 

 in 100 gallons of water did not burn l3eet foliage, and the same would 

 be true of chard and the ornamental plants which this species attacks. 

 AMiale-oil soap at the rate of 8 pounds to 100 gallons of water is 

 added, and serves as an effective adhesive agent or " sticker," thus 

 enabling a more even distribution of the poison over the leaf surfaces. 



In addition to Paris green, Mr. Marsh demonstrated that nicotine 

 sulphate, used at the rate of 1 fluid ounce to 4 ounces of whale-oil 

 soap and 4 gallons of water, sprayed upon cabbage, resulted in the 

 destruction of other small and larger larva\ He expresses the belief 

 also, reasoning from analogy, that this formula, although not actually 

 tested on Hymenia larva^, would probably prove entirely effective. 



Arsenate of lead and arsenite of zinc should both be tested for this 

 insect should it occur in numbers and an oi)port unity be afforded for 

 an early application of these poisons as spra3'^s. The most important 

 item in the control of this insect is the detection of injury early in the 

 season, before actual damage is accomplished. Among other remedies 

 fall i^lowing should be practiced. Tt is unwise to grow susceptible 

 ])lants in the same locality in which tliis insect has been abundant 

 the previous season. 



There is no proof as yet that as far north as the District of Colum- 

 bia this species will in the near future renew attack or Ix^come as bad 

 a pest as in 1012. The possibility exists, however, and a close look- 

 out will l)e kept for its reappearance. 



