2 Department Circular 263, U. S. Dept. of Agriculture. 



Such being the critical situation, the hiboraton- of the Bureau of 

 Entomology at Bentonville. Ark., began, as soon as practicable in 

 the fall of 1921,- a series of experiments for the control of the San 

 Jose scale. Of all the insecticides used in the experiments best re- 

 sults were obtained with the so-called paraffin-oil or lubricating-oil 

 emulsion. The selection of oils of this type for experimental work 

 against the San Jose scale was in consequence of the excellent results 

 obtained with lubricating-oil sprays by W. W. Yothers. of the Bureau 

 of Entomology, in the control of various citrus insects in Florida. 



A preliminary announcement " of results in the use of lubricating 

 oils for the San Jose scale was made as soon as sufficient evidence had 

 been obtained to indicate strongly its suitability for this insect. 

 This circular gives results obtained to date in the experiments with 

 lubricating oils for the control of the San Jose scale, together with 

 methods for the preparation of the emulsion and recommendations 

 for the use of the insecticide. Investigation of this subject is being 

 continued to obtain further information on the use of the emulsion 

 in various parts of the country, and on various host plants, and to 

 ascertain what injury, if any, will result to the various classes of 

 deciduous fruits treated. 



HISTORY OF INFESTATION. 



During the season of 1918 the San Jose scale caused little or no 

 damage to fruit or trees in northwestern Arkansas. At that time 

 orchardists. as a rule, applied one dormant spray of liquid lime- 

 sulphur solution in the spring just as late as possible before the 

 fruit buds began to swell. At harvest time in 1919 several orchards 

 showed fruit badly spotted with the scale, though practically no dead 

 limbs or trees were evident. The beginning of the serious scale in- 

 festation in this region dates from the fall of 1919. In 1920 a large 

 number of orchards were badly infested with the scale, much fruit 

 was damaged, and limbs and trees were being killed. Even at that 

 time, with the exception of an occasional orchardist, little anxiety 

 was shown by the growers, as they were confident that the scale 

 could be controlled with the dormant applications. 



Orchards received little attention during the growing season of 

 1921, following the complete killing of the fruit crop by freezes in 

 the spring of that year. By the fall of 1921 the San Jose scale had 

 spread so rapidly that it could be found in practically every orchard 

 of the region, and it had either killed entire orchards or portions of 

 them in many instances. It was fully realized by this date that the 

 scale must be controlled immediately or many of the growers would 

 be driven out of the orchard business. 



FACTORS INFLUENCING INCREASE OF THE SAN JOSE SCALE. 



Several reasons can be assigned for the serious damage caused by 

 the San Jose scale in this region. Foremost, without doubt, is un- 



- The writer returned to the Bentonville laboratory of the Bureau of Entomologry on 

 November 1, 1921. after an absence of nine niontlis, and liOslie Pierce, of the Bureau of 

 IMant Industry, returned to this station about the middle of November. 



^U. S. Department of .\{rrioulture Clip Sheet 108. March 6, 1922. "A Promising New 

 Treatment for the San Jose Scale," by A. L. Quaintance. 



