18 The Colorado Experiment Station. 
tested, and the Triumphs, which we had sprayed, were exceedingly 
clean. The difficulty experienced in spraying trees so late in the 
season, lies in the fact that the leaves always tend to curl and pro¬ 
vide such protection for the lice, that only the most thoro work can 
result in much good. 
TIIORONESS NECESSARY TO SUCCESSFUL SPRAYING. 
No matter when the spraying may be done for the control of 
this insect, success cannot be attained unless a very thoro applica¬ 
tion of the insecticide is made. In fact, this is a general rule that 
will hold good in spraying for the control of all insect pests. While 
this point is always emphasized by entomologists, our experience 
with orchardists has been that many do not have a proper concep¬ 
tion of what thoro spraying means. This may be due in part to the 
failure to appreciate the fact that insects multiply tremendously in 
a short time, and unless a spray kills practically all of a pest, such 
as the one in question, a few days or weeks may see them as plenti¬ 
ful as they were before the spray was applied. Spraying investiga¬ 
tions in the orchard indicate, also, that much of the trouble is due 
to the expense of a proper treatment. Most of the insecticides used 
are very high priced, and the orchardist does not feel that he can go 
to the expense necessary to thoroly treat his trees. He very often 
fails to realize that work such as this, half done, is really work 
wasted, to say nothing of the expense. 
It is safe to say that spraying for the control of the green 
peach aphis can only be successful when very great care is used to 
thofoly drench every portion of infested trees. 
conclusions. 
1. Lime and sulfur, both Rex and home prepared, Black Leaf 
extract, Black Leaf “40,” and soluble oil, may be effectively used 
for the control of the green peach aphis when applied in the early 
spring just as the eggs are hatching. 
2. A lime and sulfur spray is not effective when applied two 
weeks or more, after the eggs are hatched, for at this time the stem- 
mothers are mature, or nearly so, and are able to resist the action 
of this insecticide. 
3. Good tobacco preparations may be used with success any 
time after the aphids hatch, but it is more difficult to succeed late 
in the spring, because it is then more difficult to get the spray on 
all the lice, on account of the protection of the leaves. 
4. The best time to spray for this insect is in the early spring 
when the eggs are hatching. 
Table II, giving results attained in killing eggs and newly 
hatched lice of the green peach aphis on small trees in the W. C. 
Strain orchard at Clifton : 
