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Sumatra. The derris roots, which may be dry or fresh, are cut into small 
pieces, placed in a little water, and then pounded into a paste, which is 
diluted with a gallon of water and left standing overnight in a wooden 
vat. The dregs are then pressed, and all the fluid is strained through 
a cotton cloth. The resultant concentrate is a milk-white solution, which 
keeps for a few days only. It is diluted with 9 parts of water for spray- 
ing. About 16 imperial gallons of solution are needed for 1,000 tobacco 
plants that have been from 25 to 30 days in the field. Twice this quantity 
is needed for full-grown plants. If derris roots are to be stored they 
must be kept dry. 
The Deli Proef station at liedan (67) in 1926 reported that akar toeba 
extract gave excellent control of aphids on tobacco. Some difficulty was 
experienced in obtaining a uniform extract, so this was' prepared with the 
machinery of the Delische Kleiindustrie. Formalin was added, to a concen- 
tration of 2.5 percent as a preservative. The proefstation (68) in 1927 
reported that derris extracts (suspensions of the milky sap in water), 
supplied by the proefstation to tobacco growers, retain their toxicity 
for at least 1 year when kept in well-closed barrels. Decomposition occurs 
in open vessels and in those not hermetically closed. The suspension 
becomes gray or nearly black, develops the odor of hydrogen sulfide, and 
loses effectiveness. Contact with iron is stated to be undesirable. 
Redecker (229) in 1926 called attention to the large-scale use of 
aqueous derris extract in Sumatra for destroying aphids on tobacco. 
W, A, Foote, American Consul at Medan, Sumatra, in May 1929 sub- 
mitted a report to the United States Bureau of Foreign and Domestic 
Commerce on the use of derris in fighting tobacco plant pests. Against 
tobacco lice an aqueous extract of fresh derris root at 1:40 is more 
effective but slower than 3 percent of nicotine with soap. In 19 31 
Foote (#L06) reported that a liquid contact insecticide prepared from 
derris was used against the tobacco aphid in Sumatra. Hand pumps were 
more effective than power sprayers in applying it. 
Braddock (20), American Vice Consul at Medan, Sumatra, in 1930 
reported that derris is used on practically all the tobacco estates 
to combat aphids. The insecticide is prepared by the Deli Proefstation 
and supplied to the planters at cost. The station supplied the following 
quantities (expressed in liters) of derris extract to the tobacco growersj 
In 1926, 35,000j in 1927, 77,000; in 1928, 56,000; and in 1929, 65,000. 
The Wageningen Plantenziektenkundigen Dienst (292) in 1933 reported 
that derris extract had long been used for the control of leaf aphids in 
the Deli tobacco fields, and for some time had been a' constituent of 
proprietary extracts. 
Hendren (l_46_), American Trade Commissioner at Ratavia, Java, in 1931 
reported that tuba (derris) extract is an excellent remedy for aphids on 
tobacco in Java, 
