458 



JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 8 



more than 50 per cent. This loss, together with the other losses that 

 must be considered in the form of scab, codling moth, bruises, etc., 

 make it imperative that some means be employed in reducing this 

 waste. 



In order to determine the most advantageous method that could be 

 employed under Hood River conditions, a series of experiments em- 

 bracing lead arsenate in various strengths, crude oil emulsion, kero- 

 sene emulsion, distillate emulsion and a miscible oil w^ere used during 

 the past spring. 



Owing to the fact that it is necessary to make four or five spring 

 and early summer applications of a fungicide for apple scab control 

 in Hood River, lead arsenate, if efficient, seemed to offer the least 

 expensive plan (at least from the standpoint of labor) in bringing 

 about leaf-roller control, for this material is usable in combination. 

 Six different plans of procedure were outhned. Lime-sulfur was the 

 fungicide employed throughout the season. Spraying in the spring 

 began in what is termed at Hood River the delayed dormant spraj^, 

 or an application applied at a time when the more advanced fohage 

 has reached the size of squirrels ears. At this season it was very 

 difficult to find any hatched leaf-roller eggs. 



The orchard in which the experiments were conducted is planted to 

 Spitz enburg apples which are now about twelve years old. Two 

 rows across the orchard were used in each experiment. Between 

 each was left one as a check. In referring to the table it will be seen 

 that countings from each of these rows serve as a check on two experi- 

 ments. The degree of infestation, based on the presence of egg masses, 

 indicated that it was at least typical of the conditions as existing in the 

 valley. A power spraj^er fitted out with a ^^New Way" engine and 

 two leads of hose was employed throughout the season in apphdng 

 the materials. Frembo nozzels with a medium sized hole in the disc 

 were used. 



Two essentials were considered in the scheme of the arsenate exper- 

 iments: first, to determine, if possible, the least amount of poison 

 that must be used in bringing about control, and second, to determine 

 if possible the insect's most susceptible period to poison. 



With these thoughts in mind, six experiments were outlined. Refer- 

 ring to the table it will be seen that in all six experiments, lead arsenate 

 was used in the delayed dormant application, that the poison might 

 be present as the worms hatched. In the delaj^ed dormant spray 

 lime-sulfur was used at the rate of 1 to 18 throughout. To this fungi- 

 cide was added in experiment 1 and 3, arsenate of lead (paste in all 

 cases) at the rate of 2 pounds to each 50 gallons; in experiment 2 and 

 4, 4 pounds to each 50 gallons and in experiments 5 and 6, 6 pounds 



