4 BITLLETIlSr 969, U. S. DEPARTMENT OF AGEICULTTJEB. 



vations. These studies revealed the fact that there are two full 

 broods of larvae and a partial third during the growing season in the 

 Grand Valley and that these overlap to a certain extent, some larvae 

 hatching practically every day. In general, the hatching of each 

 brood of larvae 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.® 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 and in a 

 few smudged orchards located elsewhere. 



The apple orchard of Mr. Gus J. Johnson, of Highland Park, was 

 among those that were partly saved by the timely use of oil heaters, 

 and was available for experimental purposes. (PI. 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. Bordeairx 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, II, 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 larvae 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. Bui. 932, Tbe Life History of the Codling Moth in the Grand 

 Valley of Colorado, by the present authors. 



