12 BULLETIN 1201, U. S. DEPARTMENT OE AGRICULTURE. 



this table the results obtained by spraying the extracts of "cube," 

 clerris, and pyrethrum, and the nicotine sulphate upon Macrosiphum 

 sp. A are the same as recorded in Table 5. 



The extracts+soap+water (2, 1, and 1/2+2+100) of "cube," those 

 of derris (2 and 1+2+100), and nicotine sulphate (1/400) +soap+ 

 water (2.5+2+100) are equally toxic against Macrosiphum rosae 

 (none over half grown); while pyrethrum extract (2+2+100), 

 derris extract (1/2+2+100), and nicotine sulphate (1/800) are about 

 equally toxic, but the pyrethrum extracts (1 and 1/2+2+100) were 

 less toxic and were inefficient. 



The potato aphis (M. solanifolii), living on the pubescent under- 

 side of the leaves of a western jimson weed (Datura meteloides 

 Dunal), were particularly difficult to kill. Nicotine sulphate (1/400) 

 with soap (2+100) killed only 75 per cent of them within 24 hours, 

 and nicotine sulphate (1/800) only 60 per cent; but when the soap 

 was doubled, 95 per cent of the aphids were killed by each of the 

 nicotine sulphate solutions. The extracts+soap+water (4+4+100) 

 of " cube," derris, and pyrethrum were found efficient against this 

 aphis, but a " cube " extract (2+2+100) killed only 50 per cent of 

 them within 24 hours. The most satisfactory mixtures tested on this 

 aphis were kerosene emulsions containing the extracts. The ex- 

 tracts+water (1+100) of "cube," derris, and pyrethrum+2.5 per 

 cent of kerosene emulsion were about equally toxic and efficient; 

 while the pyrethrum extract (2+100), derris extract (1+100), and - 

 "cube" extracts (1 and 1/2+100), each +1.25 per cent kerosene 

 emulsion, were efficient; but the pyrethrum extract (1 and 1/2+100), 

 and derris extract (1/2+100), each +1.25 per cent of kerosene emul- 

 sion, were inefficient. The extracts + soap + water (1+4+100) 

 killed about 20 per cent of the aphids, while the control mixture 

 containing 2.5 per cent of kerosene emulsion killed only 15 per cent 

 of the aphids sprayed. This shows the effect of adding the extracts 

 to the kerosene emulsion. 



Table 6 shows that these alcoholic extracts are very promising 

 insecticides, although not all of the 11 species of aphids tested were 

 easily killed by them. Regarding the minimum dosage required to 

 produce efficient killing, which is here considered 90 per cent or more 

 within 24 hours, it appears that " cube " extract is 12 times as toxic 

 as pyrethrum extract and 3 times as toxic as derris extract. These 

 differences in toxicity are partially explained by the fact that the 

 concentration of the " cube " extract is 5.29 per cent, while the con- 

 centrations of the derris and pyrethrum extracts, respectively, are 

 2.89 per cent and 4.08 per cent. Relative to the following four insec- 

 ticides used with soap (2 pounds to 100 gallons of water) , the lowest 

 concentrations found which produce efficient killing are : Pyrethrum 

 extract from 2 pounds of powder, derris extract from one-half pound, 

 " cube " extract from one-sixth pound, and 40 per cent nicotine sul- 

 phate (1/1,200 strength). 



Various extracts from u cube " against aphids. — Reference to Table 

 7 shows the comparative results obtained by spraying five species of 

 aphids with various " cube " extracts. Practically no difference in 

 toxicity between the cold and hot alcoholic extracts is shown. The 

 resin was inefficient in all tests, and consequently contains only a 

 portion of the toxic principle present in this plant, but in the 



