Aug. 15, 1919 



Derris as an Insecticide 



193 



In one test several hundred flies were liberated in a room which had 

 been thoroughly dusted seven days before. Twenty-four hours later 

 very few active flies were to be seen, and on the second day only three 

 or four were living. 



Plant insects. — Derris applied as a dust was of no value against the 

 mealy bug {Pseudococctis citri Risso), the Orthezia {Orthezia insignis 

 Doug.), red spiders (Tetranychus bimaculatus Harv.), and the crawling 

 young of the oyster-shell scale (Lepidosaphes ulnii L.) ; but it was eff"ective 

 against nasturtium aphids {Aphis rumicis L.) and the green apple aphis 

 {Aphis pomi De Geer). 



DERRIS APPLIED AS A SPRAY MIXTURE 



Derris applied as a spray mixture was tested against the green apple 

 aphis {Aphis pomi De Geer) under field conditions and was found to be 

 very effective. Young apple trees, about 10 feet high, were used. The 

 spray mixtures were applied with a knapsack sprayer, except in tests 

 No. 3 and 6, in which a barrel sprayer was used. When soap was used 

 it was employed at the rate of i pound to 25 gallons of water. One 

 dusting experiment was performed, the powder being applied with a 

 large hand duster. 



Table VI. — Results of field tests, using Derris powder in spray mixtures and as a dust 

 against the green apple a phi (Aphis pomi De Geer) 



No. of 

 test. 



3 

 4 

 5 

 6 



7 

 8 



9 

 10 



Ratio of powder to water or soap solution used, dusting test, and 

 controls. 



I pound of powder to 25 gallons of water 



I pound of powder to 50 gallons of water 



do 



I pound of powder to 50 gallons of soap solution . 



I pound of powder to 100 gallons of water 



do 



I pound of powder to 100 gallons of soap solution 



I pound of powder to 150 gallons of water 



I pound of powder to 150 gallons of soap solution 



I pound of powder to 200 gallons of water 



I pound of powder to 200 gallons of soap solution 



Dusting test 



Control , soap solution only 



Control, trees untreated 



Num- 

 ber of 

 trees 

 used. 



5 



5 



32 



3 



52 



5 



5 



5 

 5 

 5 



Dura- 

 tion of 

 tests. 



Days. 



3 

 3 

 4 

 3 

 3 

 4 

 3 

 3 

 3 

 4 

 3 



Aphids 

 killed. 



Per cent. 

 100 

 ICO 



95-100 



100 

 100 

 80-90 

 100 

 100 

 100 

 "98-100 



"98- 1 GO 



100 



O 



O 



a Four trees entirely free of aphids. 



Table VI shows that Derris, even at the rate of i pound to 200 gallons 

 of water, was very effective against the green apple aphis under field con- 

 ditions and that on apple foliage the addition of soap does not increase 

 its effectiveness. It also shows that this powder is effective as a dust. 



Under greenhouse conditions, in tests against the nasturtium aphis, 

 this material was found to be effective when used at the rate of i pound 



122501 



