December, ’24] 
SHEDD AND OLNEY:TOBACCO EXTRACTS 
653 
would have contained about .05 per cent. The strength generally rec¬ 
ommended is from .05 to .07 per cent. 
The solutions were applied to aphis on tomatoes in the greenhouse 
and on plum trees in the open. The results were about the same with all 
samples. All small or medium sized aphis were killed in 2 hours and 
practically all the remaining or large ones after 24 hours. The number 
under observation in the individual experiments generally was two to 
five hundred and it was noticeable that the few which survived after 24 
hours’ observation were all full-grown. The-medium sized and small 
ones were always killed. The highest percentage surviving was 3 per 
cent, in only one case, but generally only about 1 per cent, by actual 
count, survived after 24 hours. 
The foregoing results were obtained with freshly prepared solution. 
One of these solutions which, when fresh, had killed all the aphis, was 
tried again after standing for nearly a week; it was found to exterminate 
only 82 per cent of the aphis. In the meantime, however, the decoction 
had commenced to ferment and had developed a disagreeable odor. This 
indicates that the fresh solution should be used or some preservative 
added. 
One tobacco was tried on aphis by taking the fresh solution which was 
found to exterminate all and diluting it with 1, 2, 4 and 8 parts of water. 
The degrees of extermination after 24 hours’ observation were 76, 79, 
30 and 11 per cent, respectively. The aphis in the experiment which 
gave 79 per cent extermination were smaller than the others, which 
accounts for a larger number killed in this case. In all cases, the surviv¬ 
ing aphis were of the larger size. It appears from these particular ex¬ 
periments that the solution should contain at least .05 per cent of nicotine 
for effective results; in fact, it might be preferable for it to have about 
.10 per cent to get rid of all mature aphis in a few hours where it was to 
be applied in the open with a probability of rain washing it off before 
all were killed. 
The results clearly demonstrate that if recommendations are to be 
made for preparing sprays from tobacco the nicotine content of which 
is not known, a very low percentage would have to be taken as a standard 
for any particular variety, otherwise unsatisfactory results would fre¬ 
quently be obtained. On the other hand, by accepting such a low stand¬ 
ard, some solutions would necessarily carry very much larger amounts 
of the alkaloid than is desired, due to its higher percentage in the samples 
from which they were prepared. 
