104 ANM'Al. REPORTS OF DEPARTMENT OF AGBICXJI/TUBB, 1940 
the extermination of the insect, the application of the insecticide this 
year with improved equipment at the 3n-pound dosage should he 
ent irely satisfactory. 
I NSK( TIC IDF I N V ESTIGATK I N - 
Research to develop new and more effective insectides was actively 
prosecuted, and the results were made available to the public by means 
of 39 scientific publications, comprising *2 department circulars, 3 
articles in the Bureau's E series, and 34 articles in technical and trade 
journals. Twelve patents were issued to members of the Division, and 
the monthly review of United States patents relating to pest control 
M as issued regularly and distributed to a large Dumber of foreign and 
American entomologists.' 
INSECTICIDAL PLANTS (TOBACCO. DERRIS. PYRETHRUM, ETC), AN I) 
THEIR CONSTITUENTS 
Numerous species of Nicotiana^ the genus of plants to which tobacco 
belongs, and hybrids produced by crossing them, were examined to 
determine how much nicotine they contain, whether other alkaloid- of 
insecticidal value are present, and what relation the alkaloid of the 
hybrids hears to that of the parents. Further attention was also 
devoted to the solid compounds of nicotine, one of which, nicotine 
hentonite, is the most promising organic substitute for lead arsenate 
for the control of codling moth larvae. A study was made of different 
bentonites on the American market, and a procedure was developed 
for making a nicotine bentonite that does not build up such an un- 
sightly deposit on fruit and foliage as does the tank-mix product. 
The chemistry of hentonite in relation to base exchange was investi- 
gated to obtain fundamental knowledge helpful in the study of nicotine 
bentonite. An improved method for the separation of nicotine from 
anabasine, nornicotine, and related alkaloids was worked out. New 
analytical procedures for the quick and accurate determination of 
minute quantities of nicotine, such as would occur in spray residues of 
nicotine bentonite. were perfected, and nornicotine was found to be 
the predominating alkaloid in a specimen of Maryland tobacco. 
The importation of the roots of derris from the East Indie- and of 
cube and timbo (Lonchocarpus) from South America has increased 
greatly. First brought in less than 1<) years ago, in L939 there were 
imported 2.335.04s pounds of crude derris root. 1,907,194 pounds of 
crude cube and timbo roots, and 896,640 pounds of powdered roots. 
These roots contain rotenone and rotenoids (deguelin and related 
compounds), which are among the most potent insecticide- known. 
Extracts of these root- are used in fly -prays and greenhouse sprays, 
and the powdered root- mixed with talc or other diluents have a wide 
use in combating the pea aphid, the pea weevil, the Mexican bean 
beetle, and cabbage caterpillars. 
Accomplishments during the year include the finding of a minute 
quantity of alkaloidal material in derris, cube, and timbo roots, which* 
however, proved nontoxic t<> mosquito larvae. An improved method of 
dispersing the insecticidal constituents of derris. pyrethrum, and other 
riant materia] was developed in cooperation with entomologists of the 
)i vision of Control Investigations. It consists in burning the pow- 
dered material under Mich condition- that a dense smoke is formed, or 
in spraying an extract in a suitable organic solvent upon a heated 
