- 5 - 
Dorris, even. at the rate of 1 pound to 200 gallons of water, was 
very effective against the green apple aphid imder field conditions. On 
apple foliage the addition of soap does not increase its effectiveness. 
This Tjcv/der is also effective as a dust. 
Under greenhouse conditions, in tests against the nasturtium aphid, 
this material was foiond to be effective when used at the rate of 1 pound 
of powder to 400 gallons of water, with soap at the rate of 1 pound to 
100 gallons. 
Oyster- shell scale: At the rate of 1 pound of powder to 20 gallons 
of v/ater, either with or without soap in the proportion of 1 pound to 100 
gallons, derris was ineffective against the crawling young of the oyster- 
shell scale, Lepi do saphe s ulmi L. 
The efficiency of derris as a stomach poison against various insects 
was also tested. 
Potato "beetle larvae: Derris powder as a stomach poison was tested 
on a small scale against potato beetle larvae, Leptinotarsa docemlineata Say, 
at several strengths, ravaging from 1 pound of powder to 15 gallons of water 
up to 1 pound to 128 gallons and was found to be very effective. Practically 
all the larvae were killed within 46 hours and the plants were little eaten. 
Since these spray mixtures mi.^ht have acted as contact poisons, 
because the larvae were already on the plants when the latter were spraj'"ed, 
a second series of tests was arranged to eliminate this factor. The same 
plants were used and from 20 to 40 larvae were placed on them 1 or 2 days 
after they had been sprayed. The results obtained were practically the 
same as in the first series of tests. Very few living larvae were found 
three days later and the plants were little eaten. When applied as a 
dust, derris was equally efficient against potato beetle larvae. 
Tent caterpillars: Derris was tested against young tent cater- 
pillars, I.ialacosoma. a mericana F. , in a series of strengths ranging from 
1 pound of powder to 8 gallons of water to 1 pound to 200 gallons. 
All the mixtures were found to be effective. Apple-tree branches were 
thoroughly sprayed, and after the foliage had dried 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 v/?s any material amount to feeding 
observed. 
In a second series of tests the larvae were placed on the branches 
and spreved after they had begun to form their tents. Under these con- 
ditions sprays containing 1 poiind of powder to 50 gallons of water and 
1 pounfi to 100 gallons killed ^11 the larvae within 24 hours. V.'hen 1 
pound to 200 gallons and 1 pound to 400 gallons were used, all the larvne 
were not killed within 11 davs, but the few which remrined alive v;ere 
verv small r.nd inactive. Used ?s a dust, this material killed all the 
treated larvf^e within 1 week. 
