LONCHOCARPUS, DERRIS, AND PYRETHRUM CULTIVATION 27 
cemmercial production was begun, and a year later the Kenya 
Pyrethrum Growers’ Association was formed (1/2). This association, 
through the official pyrethrum board, which it elects, has standardize d 
classification, price, and marketing procedures in a way that has 
proved highly profitable to the Kenya growers, who by 1940 were 
supplying the United States with over 82 percent of its requirements. 
During the recent war years United States imports from Kenya tem- 
porarily decreased somewhat, whereas supplies from two important 
new producing areas, the Belgian Congo and Brazil, advanced con- 
siderably. 
BOTANY 
Several species of the genus Chrysanthemum have been. reported to 
possess insecticidal properties, but only three are recognized as 
worthy of consideration: C. coccinewm (also known as C. roseum), C. 
marschallii, and C. cinerariaefolium. Of these the last-mentioned is 
so superior that it has become almost the exclusive source of commer- 
cial pyrethrum. This plant, and especially its flower, is similar in 
appearance to the common field daisy, C. leucanthemum, which is of 
no value as an insecticide. C. cinerariaefolium is a perennial, which 
when mature may produce floral stems 18 to 30 inches tall. Under 
cultivation, single plants grow into large mats, ordinarily 8 to 15 
inches in diameter at the crown. The leaves may be distinguished 
from the common daisy in that they are deeply lobed, usually into 
three primary divisions, and the lobes are more or less deeply cut. 
The floral stems are long, usually erect, and nearly without leaves. 
The heads have white rays and yellow disk florets. Over 80 percent 
of the insecticidal pyrethrins are concentrated in the ovaries of fully 
opened flowers. Martin and Tattersfield (27) analyzed segments of 
fully open flowers with at least one-quarter of the disk florets open 
and no parts missing. They found the following distribution of 
pyrethrins in the various floral parts: 
Composition Total 
of flowers pyrethrins 
Floral parts: (percent) (percent) 
ECE LES UIs eg = EAS a, Se a ee ae ne ee 25. 2 0. 18 
Receptacles, and involucral scales_ =. =-__...=.-___ =. 20. 4 Pb 
Disko tloress;.excludimp Ovaries. = 9.45. ee 31. 4 . 48 
SD iaVicn eee ee ere Ce A Be = 2330 4. 54 
CULTURAL PRACTICES 
Commercial pyrethrum is propagated both by seed and by rooted 
crown. divisions commonly called “splits.” Most research workers 
agree that over a period of years plants grown from seed produce 
larger total yields than those propagated by splits. Seedlings are 
generally germinated in specially prepared nurseries and later trans- 
planted to the field (fig. 15). Usually they do not flower until the 
second year, but thereafter they may bear. heavily for 3 to 4 years, 
and, even though yields may then decline, plantations may con- 
tinue to produce e satisfactorily for a few additional years. In the 
Tropics plants grown from splits will begin flowering within several 
weeks after they are set in the field. In the United States a satisfac. 
tory crop is on obtained until the second year. The yields and 
economic life of plants grown from splits may be less than those of 
q 
