-45- 
per acre cnecked the increase of thrips for a longer period than a 1 per- 
cent DDT dust, and the 1-percent dust prepared -with methyl naphthalenes 
[VelsicolJ was more persistent in its effects on the thripa population 
than the 1-peroent dust prepared with aoetone. In a field test better 
control of thrips was obtained with the DDT treatments than with nico- 
tine sulfate. A DDT dosage of 2 pounds of 20 percent material with soap 
gave almost as good results as the 5-pound treatments. The increase in 
yield of the DDT-sprayed plots over tne nicotine-sprayed plots was be- 
tween 70 and 87 (100-pound) sacks of onions per acre. These figures 
adequately illustrate the value of keeping the thrips population under 
control.— Jeppson and Borden (226 ) . 
In the greenhouse a powder suspension containing 8 ounoes of DDT 
per 100 imperial gallons of water gave excellent control (98 percent 
reduction over check) of thrips on potted onions. In the field one appli- 
cation failed to give more than a very temporary reduction in the popula- 
tion. Pour days after spraying with formulations containing 16 ounces of 
DDT the average population per plant was 6.8 with the powder suspension, 
16.0 with the Velsicol emulsion, and 77 in the check plots. However, 
within 9 days after treatment there was no appreciable difference between 
the treated and the untreated plots* Apparently few of the larvae at the 
base of the plant within the proteotion of the leaf sheath were killed. 
— Ross (506) • 
Preliminary laboratory tests with several concentrations of DDT 
dusts and sprays showed a definite possibility for controlling onion 
thrips, especially with the higher concentrations of DDT.— Granovsky (187) « 
A DDT aerosol produced excellent kills of thrips on onions*— Ditstan 
(155 )* 
Unidentified thrips 
Under greenhouse conditions, 1 pound of DDT per 100 gallons of water, 
applied approximately every 2 weeks, controlled thrips and reduced spotted 
wilt of tomatoes more effectively than did frequent fumigation with nico- 
tine. However, the treatment seriously damaged the plants, and it can- 
not be recommended unless further experiments show that such injury can 
be avoided. The composition of the spray was: 5 pounds of AK-20 contain- 
ing 20 percent of DDT, 6 ounces of blood albumin, and 100 gallons of 
water*— Gardner &t ej.. (164 ) • 
A 5-peroent DDT dust was effective against thrips on chrysanthemums* 
— Haseman (203) * 
A fog made by feeding DDT in oil solution into a current of steam 
was affective in the Salt River Valley, Aril., against thrips on grape- 
fruit trees, beets >and cauliflower •— Anon* (49)* 
