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Thrlps fusoipennis Haliday, a rose thrips 
In tests against this thrips on roses in England, 3 days elapsed 
before derris powder caused appreciable mortality. A spray of 2 
pounds of derris powder and 10 pounds of soft soap in 100 gallons of 
water on some occasions gave total mortality in 24 hours, but on other 
occasions it failed to do so in 4 days.— Speyer (568 , p. 64) • 
Thrips lini Lad., a flax thrips in Holland 
Experiments have shown that derris is valuable, but on biological 
grounds the value of insecticides against this thrips on flax in 
Holland is doubtful.— Doeksen (148 ). 
Spraying with derris powder in water (rotenone: 1:5,000) proved 
very successful in field tests. Dusting and spraying with derris 
gave better results than with nicotine. Dusting gave better results 
than spraying.— Spoon (561 , 562 ). 
The best control of this thrips in Holland was obtained by dust- 
ing with derris powder (l percent of rotenone) at the rate of 36 pounds 
per acre while the plants were wet with dew.— Wolters (700) • 
Thrips tabaoi Lind., the onion thrips 
Rotenone sprays or dusts did not give satisfactory control. Onion 
plants treated with an emulsified oil-rotenone extract were severely 
injured.— Anderson and Walker (17). 
In field tests in 1940 a spray of nicotine sulfate and soap was 
superior to any other inseoticide, having given 95 percent effective 
control. Sprays containing rotenone and oil, nicotine with oil, and 
derris alone or with talc or clay were superior to sprays of pyrethrum 
with oil or sulfur. Derris showed a marked residual effeot, and its 
effectiveness was somewhat improved by the addition of talc or clay. In 
1942 a rotenone extract with a resin residue spreader had a high im- 
mediate effect and good residual action. Derris powder (4 percent of 
rotenone) gave excellent kill within 24 hours, and reinfestation was 
slow. The residual effect of nicotine sulfate and soap was inferior to 
that of rotenone. In 1943 nicotine sulfate with soap was superior to 
all other treatments, having given 87 percent reduotion of onion thrips. 
A commercial rotenone solution was nearly as effective and gave greater 
residual protection.— Bourne (69, p. 58; 70; 72, p. 35). 
