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



opened, so as to take advantage of warm weather. Commercial 

 liquid lime-sulphur s"olution was very generally used, although a few 

 growers preferred miscible oil occasionally. When the scale began 

 to increase, two dormant sprays were more frequently applied, one 

 in the fall after the foliage was off and a second in the spring. At 

 the same time many growers increased the strength of their spray 

 mixture from the recommended 25 gallons of 33° Baume lime- 

 sulphur solution to as much as 35 or 40 gallons in a 200-gallon spray 

 tank. In spite of this the majority of growers failed to obtain a 

 satisfactory control of the scale. On incrusted trees enough scales 

 escaped to provide breeding stock for the following season. A few 

 growers, however, were able to control bad infestations of the scale 

 with two thorough applications of lime-sulphur. In such instances 

 all parts of the trees were thickly coated with spray, which required 

 an unusually large amount of spray material on each tree. 



The expense involved in making two dormant sprays with lime- 

 sulphur solution, together with the unsatisfactory control obtained, 

 led the orchardists to welcome any new methods to fight the scale. 

 When it was found that lubricating-oil emulsion gave a splendid 

 killing of the scale, the growers were enthusiastic about using it. 



SPRAYING EXPERIMENTS IN THE FALL OF 1921. 



A block of young Early Harvest trees, so badly incrusted with the 

 scale that many limbs had already been killed, was obtained for the 

 spraying experiments in the English & Boles orchard at Benton- 

 ville, Ark. The experiment consisted of 26 plats, and included tests 

 of several different strengths of lubricating-oil emulsion, kerosene 

 emulsion, a proprietary miscible oil, several brands of dry lime- 

 sulphur, three brands of commercial liquicFlime-sulphur, and home- 

 made lime-sulphur solution. The spraying was done with a barrel 

 spray rig Avhich maintained a pressure of about 125 pounds for a 

 single rod with one nozzle. The trees were small enough to avoid 

 any difficulty in covering their entire surfaces by means of this outfit. 

 The tests were made during the middle of December, 1921, after the 

 trees were completely defoliated and before cold weather had begun. 

 Each plat consisted of at least 4 trees, and examinations to deter- 

 mine the mortality of hibernating scales were made under a binocular 

 microscope from twigs of 4 record trees. 



All oil emulsions were made by the boiled process, and potash fish- 

 oil soap was used as the emulsifying agent. No examination of twigs 

 at the time of first-generation hatching or of the fruit at harvest time 

 was made. Observations of the fruit on the oil-emulsion sprayed 

 plats, however, showed scarcely any scale spotting at picking time. 



Table 1 giA^es a summary of the experiment, showing the various 

 insecticides and dosages used, with the percentage of dead scales in 

 each plat at the time of examination. It requires about 30 days after 

 spraying with oil emulsions before absolute determination of dead 

 scales can be made. The killing poAver of lime-suli:)hur extended over 

 a considerably longer period than that of oil sprays. 



The results from the dry lime-sulphur plats are not included in 

 this circular. 



