196 Journal of Agricultural Research voi. xvii, no. s 



Apple tree branches were thoroughly sprayed, and after the foliage 

 had dried from 20 to 40 newly hatched larvae were placed on each branch. 

 The caterpillars began to show signs of discomfort within 48 hours and 

 were practically all dead in from 5 to 10 days. In no case was any mate- 

 rial amount of feeding observed. 



In a second series of tests the larvae were placed on the branches and 

 sprayed after they had begun to form their tents. Under these condi- 

 tions sprays containing i pound of powder to 50 gallons of water and i 

 pound to 100 gallons killed all of the larvae within 24 hours. When i 

 pound to 200 gallons and i pound to 400 gallons were used all thelar\^ae 

 were not killed within 11 days, but the few which remained alive were 

 very small and inactive. 



Used as a dust, this material killed all of the treated larvae within one 

 week. 



Fall WEbworms. — These caterpillars (Hyphantria cunea Dru.), about 

 one-third grown, were killed within a week by a spray containing i 

 pound of powder to 5 gallons of water. Mixtures ranging from i pound 

 to 50 gallons to i pound to 200 gallons were not satisfactorily effective, 

 since nearly all of the sprayed foliage was eaten and not all of the cater- 

 pillars were killed. 



Oak worms. — ^Two small oak trees, on which about 300 caterpillars 

 {Anisota senatoria S. and A.) were feeding, were sprayed thoroughly 

 with Derris at the rate of i pound of powder to 25 gallons of water; 

 soap was added at the rate of i pound to 50 gallons, and a knapsack 

 sprayer was used. Within 24 hours the larvae became inactive and 

 ceased to feed, and at the end of 6 days no living ones could be found. 

 As a check on this test, powdered arsenate of lead was applied at the 

 rate of i pound to 50 gallons of water, and almost identical results were 

 obtained. 



A second test was made in which a small tree was sprayed, and 24 

 hours later about 50 larvae were placed on it. The caterpillars ate very 

 little and gradually disappeared, evidently leaving the tree, since no dead 

 ones were observed; and at the end of 5 days they were nearly all gone. 



Datana larv^. — Two apple trees, on which large colonies of nearly 

 full grown apple datanas {Datana ministra Dru.) were feeding, were 

 sprayed with Derris at the rate of i pound of powder to 50 gallons of 

 water. Twenty-four hours later one living lar\^a was found on one 

 tree and two on the other. The ground under the trees was thickly 

 sprinkled with dead larvae and many had lodged in the trees. 



Cabbage worms. — In two cage tests against cabbage loopers (Auto- 

 grapha hrassicae Riley), Derris, applied at the rate of i pound to 25 gallons 

 of water, killed all of the larvae within 24 hours. 



