1013.] PUBLIC DOCUMENT — No. 31. 91 



purpose. Elm-leaf beetle larvjc were abiiiidaiit on the elm, but 

 the application to the other plants was entirely to determine the 

 dan<i(r of injury to the foliage. 



In all cases the sprayed leaves were conspicuous until the 

 leaves turned in the fall, indicating an excellent adhesive pro]> 

 erty. On the elm the beetle larvre were quickly killed, and 

 after a short time injury to the leaf tissue around each place 

 where a beetle had fed became evident. 



After two weeks an examination of the plants sprayed showed 

 that all had been injured by the treatment, the material having 

 evidently been applied too strong. Tests at other places, reports 

 of which were received after the tests here had been made, indi- 

 cate the same thing, and it is now the intention to continue the 

 experiments the coming season, to determine the best strength 

 of the arsenite to use for effectiveness against insects and at the 

 same time avoid injury to foliage, using various fruit and shade 

 trees for the purpose. 



It was noted in the course of the work that the arsenite did 

 not remain long in suspension, and continuous agitation was 

 necessary to insure an even distribution. 



Zinc Arsenite. — Received from the California Spray Chem- 

 ical Compan}^, Watsonville, Cal., for trial. Tests of this were 

 made at the same time and in the same way as with the other 

 arsenite of zinc, as described above. The material appeared to 

 settle rather more quickly than the other, but no other differ- 

 ences were noticed. It is evident that in this case, also, the 

 application was too strong. It is quite certain that settling of 

 both of the samples of arsenite of zinc can be materially delayed 

 by the addition of soap, as has been shown by Parker (Mon- 

 tana Bulletin !N"o. 8G) and others. 



