6 
COLORADO EXPERIMENT STATION. 
as subject to variation with place, season, and variety. The egg ob¬ 
servations were made upon trees receiving no treatment throughout 
the season. 
HOW TIME TO SPRAY WAS DETERMINED IN EXPERI¬ 
MENTAL ORCHARD. 
Petals dropped—calyces open_May 11 
First spray_May 11 
First eggs seen_May 21 
Numbers eggs seen _...June 1 
Second spray_June 2 
First generation, eggs maximum_June 13-19 
First generation, eggs minimum_June 28 
Second generation, eggs begin_July 2 
Third spray—(suggested)_July 2 
Second generation, eggs abundant_July 17 
Fourth spray—(suggested)_July 18 
Second generation, eggs maximum_July 25-31 
Fifth spray—(suggested) _August 1 
Second generation, eggs diminished to 
about - Sept. 1 
The time in which an orchard must be completed with the first 
spraying will be of greater importance than the time required for 
second or other later sprays. Power spraying outfits make it possi¬ 
ble to cover larger orchards in less time than with hand apparatus, 
but it has been found that under ordinary conditions one good power 
outfit should not be expected to cover more than twenty acres of full¬ 
bearing orchard at the first codling moth spray. 
In apple orchards of mixed varieties those blooming first should 
be sprayed first. Pears do not close their calyces as quickly as apples, 
and their first spraying may be longer delayed. 
Kind of Spray —The experiments of the year demonstrated that 
Swift’s arsenate of lead was slightly superior to the arsenite of lime 
so far as killing effect upon worms was concerned. The difference 
seemed to be less than 4 per cent, but though the cost of the lead is 
considerably more, it is probable that with a heavy yield of fruit of 
high market value the lead would probably more than pay for the dif- 
ference in cost. It is more convenient and less liable to injure foliage. 
Other brands of arsenate of lead were used with nearly equal suc¬ 
cess in controlling the worms, but some samples had been improperly 
made and caused injury to foliage and fruit from an excess of free 
aisenic contained. Arsenite of lime, used with sufficient lime, will 
TIME TO SPRAY— 
GENERAL RULE. 
(1.) Petals off-caly¬ 
ces open. 
(2.) (a) One month 
from full bloom. 
( b ) Three weeks 
from center 
calyces closing. 
(c) When apples 
are about t in. 
diameter. 
(3) One month from 
( 2 ) 
(4) Two weeks from 
(3) 
(5) Two weeks from 
(4) 
