4 BULLETIN 959, U. S. DEPARTMENT OF AGRICULTURE. 
vations. These studies revealed the fact that there are two full 
broods of larve and a partial third during the growing season in the 
Grand Valley and that these overlap to a certain extent, some larve 
hatching practically every day. In general, the hatching of each 
brood of larve begins first in small numbers, then in increasing 
numbers until the maximum is attained, after which there is a gradual 
decrease until the last larva of the brood has hatched.2 A tentative 
spraying schedule, based on certain intervals between applications, 
was adopted and closely adhered to throughout the work, except 
when it seemed advisable or became necessary to deviate therefrom. 
SPRAYING EXPERIMENTS IN 1915. 
The growing season of 1915 was extremely abnormal in so far as it 
related to the crop of apples and abundance of the codling moth. 
The fruit crop of the valley was practically destroyed just as the petals 
had dropped by the freezes of May 2, 3, and 4. Temperatures as 
low as 22° F’. were recorded in some sections, killing apples and pears 
except at Palisades where peaches constitute the chief crop a ma 
few smudged orchards located elsewhere. 
The sore orchard of Mr. Gus J. Johnson, of Highland Park, was 
among those that were partly saved by the ile use of oil heeices 
and was available for experimental purposes. (Pl. I, fig. 1.) This 
orchard consisted of the Ben Davis, Jonathan, Black Twig, Winesap, 
and Rome Beauty varieties and was divided into 10 plats, including 
the unsprayed or check plat. 
In Tables 2 and 3 will be found data of the experiments. Two 
spray poles were used, one of which was operated from the top of the 
spray tank and the other from the ground. Bordeaux nozzles were 
used for the calyx treatment except in Plat VI, and nozzles of the eddy- 
chamber or whirlpool-disk type were employed for all cover sprays in 
all of the sprayed plats except in plat VI; in this plat Vermorel nozzles 
were used in all applications. Plats I, ile and IX, located in different 
sections of the orchard, received identical treatment, a total of four 
cover sprays, two for the first brood and two for the second and third 
broods. Plats III and IV were given five cover sprays each, the 
former receiving three for the first brood and two for the later broods 
and the latter two for the first and three for the subsequent broods. 
Plat V was given a total of three cover sprays, two for the first 
brood and one for the broods that followed. Plat VI was sprayed 
throughout the season with a very fine mist spray delivered by 
Vermorel nozzles under a pressure of 90 pounds. Two cover sprays 
were applied for the first-brood larve followed by two more cover 
sprays for the second and third broods, making four cover treatments 
in all. Plats VII and VIII were given the same number of applica- 
8 For further details see U. S. Dept. Agr. Bul. 932, The Life History of the Codling Moth in the Grand 
Valley of Colorado, by the present authors. 
