December, ’24] 
SHEDD AND OLNEY:TOBACCO EXTRACTS 
651 
tender plants. It is used more than any other insecticide to destroy 
aphis or plant lice. Various concentrated extracts of tobacco are now 
on the market and with proper dilution they can be used with unvarying 
success provided their guaranteed content of nicotine is present. Fur¬ 
thermore, they can usually be added to certain other insecticides without 
detriment to either. 
The question frequently arises whether diseased, damaged or waste 
tobacco that cannot be profitably sold may be used for the preparation 
of a spray solution. The answer would be that it can, provided its ap¬ 
proximate nicotine content is known. The nicotine content of tobacco 
varies greatly depending on many factors such as variety, fertility and 
character of soil, climate, season, curing, blight or disease and other 
possible causes. 
Tobacco stalks contain less nicotine than the stems and the latter 
less than the leaf. The leaves nearest to the ground contain less nicotine 
than the upper ones. With respect to the Burley plant, the lower leaves 
are lighter in color and go into the smoker grades while the middle and 
most of the upper ones are included in the red filler grades and wrappers. 
It so happens that at present prices, the only kinds of tobacco which 
probably can be profitably used for sprays comprise stalks, stems and 
common trash. The last consists chiefly of sweepings, refuse, and dis¬ 
eased and damaged leaf and usually contains relatively the smallest 
nicotine content of any grade. It usually has more nicotine, however 
than stalks or stems and is to be preferred when it can be obtained at a 
low cost. It seems that the factors which vitiate the quality of the leaf 
also materially reduce its nicotine content, with the possible exception 
when matured leaf cures with a green color in the barn. It is thought by 
some growers that this is caused by exposure to chilly winds in the curing. 
This color materially reduces the value but will often disappear after the 
tobacco is bulked for a short time and put thru the dryer. The nico¬ 
tine content of tobacco with this green color does not appear to be 
affected to the same extent as that of tobacco which is house burned or 
diseased. For illustration, two samples of this green tobacco were 
found to contain 1.96 and 2.38 per cent of nicotine in the air-dried 
leaf, whereas diseased tobacco was found to contain much less, as will 
be shown later. 
The Burley crop of 1920 was probably one of the most inferior ever 
produced in central Kentucky, due to the prevalance of two diseases now 
commonly known as wildfire and angular leaf-spot. These diseases 
were, also, present during the same year in the dark tobacco region of 
