396 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 15 



information on the life history of the peach twig-borer and particularly 

 how to satisfactorily control it. 



The following questions required solution: — 



1. Does lime-sulphur spray effectively control the peach twig- 

 borer? 



2. What are the relative values of lime-sulphur, its substitutes and 

 other spray materials now in use? 



3. What is the best time to apply the sprays? 



4. What is the life history of the insect? Is there a second genera- 

 tion or only one irregular brood? 



Spraying Experiments 



The work was begun in the fall of 1920. Various orchards were in- 

 spected with the view of securing heavily infested trees for the purposes 

 of the investigation. About 600 two-year-old almond seedlings at the 

 University Farm, at Davis, were selected for the experiment. Mr. 

 C. D. Gregory, of Winters, kindly volunteered the use of his apricot 

 orchard, while Mr. J. Caughy of Vacaville offered 900 plum trees for 

 spraying tests. 



Various spray materials that have been recommended for control 

 of the peach twig-borer were applied to the almond seedlings at Davis 

 at three different stages, in order to determine the proper time of 

 spraying. The experiments at Winters and Vacaville were planned to 

 test the relative values of liquid lime-sulphur and dry lime-sulphur. 



Table I shows the results of the 1921 experiments at Davis. Re- 

 sults of the Winters and Vacaville experiments are similar. 



It will be noted from the data that nicotine sulphate and zinc ar- 

 senite gave excellent control when applied as the buds were swelling 

 and at full bloom. Lime-sulphur controlled the insect only partially, 

 while the lime-sulphur substitutes and the oil sprays were not effective. 



The results of experiments in 1921 were used as a basis for more ex- 

 tensive experiments in 1922. Growers in different parts of the state 

 became eager to test suggested remedies and cooperators were se- 

 cured in Placer, Solano, and Yolo Counties. Professor Essig and the 

 writer outlined and supervised these experiments. In addition 

 to these numerous test plots, the writer, conducted experiments again 

 on the almond seedlings at the University Farm, at Davis. 



It is too early to report the results of all the 1922 experiments. In 

 most of the orchards the twig injury caused by the first generation of 

 larvae has not been enough to afford conclusive counts. The almond 

 seedlings are the only ones that showed evidence of injury and counts 



