18 THE COEORADO EXPERIMENT STATION 
within three feet of the crown of the tree and within one foot of 
the surface. It should also be remembered that the same’ sub¬ 
stances that will kill the lice above ground will also^ kill them 
below, if they can only be put in contact with the lice. The 
orchardist should be cautious, also, not to accumulate in the soil, 
about the crowns of his trees, substances that are likely, either 
presently or after years of repetition, to do his trees an injury. 
EXPERIMENTS IN GRAND VAEEEY. 
For many years tobacco, in the form of dry dust, stems or 
leaves, has been considered the best known remedy for this 
louse. Soapy solutions have also been thought of some value. In 
Bulletin 23 of the Georgia - Experiment Station (1907), Professor 
R. I. Smith, reports far better success with kerosene emulsions 
than with tobacco or soaps for the destruction of the apple woolly 
aphis upon roots. 
A rather extensive series of experiments for the purpose of 
testing substances that seemed to offer some promise of good re¬ 
sults were carried through in irrigated orchards of the Grand 
Valley in Colorado, a summary of which is given in the table on the 
following page- 
The authors are under special obligations to the men who 
kindly offered their trees for the experiments and in other ways 
aided in carrying on the work. 
THE APPLICATIONS AND THEIR RESULTS 
The experiments were begun in the fall of 1906 and the win¬ 
ter following. The materials used upon the roots were kerosene 
emulsion, Scalecide, Chloroleum, Black Leaf Dip, tobacco dust, to¬ 
bacco dust decoction, tobacco stems, tobacco stem decoction, quick 
lime, lime-sulfur mixture, Rex lime-sulfur, Adams’ lime-sulfur, 
whale-oil soap, and carbon bisulfide, as shown in the table. Other 
tests were also made upon the roots which are not scheduled. 
Before making the applications, the earth was removed over 
the main roots to a depth of about 6 inches, and for a distance 
of about 2 feet upon all sides, of each tree. One man on an average 
would expose the roots of about 100 trees a day. Into these dirt 
basins, which varied some in depth and diameter, with the size and 
depth of the roots of the trees, the liquids were forcefully sprayed 
so as to well drench the exposed portions. Both the treated trees 
and the checks were given a rating of i to 4 as to degree of in¬ 
festation, so as to be able to make fair comparisons in determin¬ 
ing results. The liquid applications were then forcefully sprayed 
upon the roots in these basins until two or three gallons had been 
applied, and when the liquid had nearly or quite soaked into the 
