ANNUAL REPORT, 1945-46 43 



At the same location other elm logs were sprayed four times at three-week 

 intervals beginning July 20, with the following results. The proportions and 

 amounts of spray materials indicated were used for each application. 



Present Control 

 Gesarol emulsion and water 



(1-400, 182 cc.) 52.9 



(1-200. 145 cc.) 2.6 



Gesarol A-20 and water (18 grams - 3785 cc, 172 cc.) 0.0 



Although no significant reduction in the number of exit holes resulted from 

 these DDT sprays, dead adults were occasionally found in the exit holes on some 

 of the infested logs which were sprayed one or more times with DDT. This 

 phenomenon was apparently not common enough in the logs sprayed with the 

 other materials to have been noticed. To what extent the DDT residue on the 

 surface of the bark may have affected beetles which completely emerged, was 

 not determined. 



The Control of Elm Scolytid Infestation by Solar Heat. (W. B. Becker.) 

 Scolytid development in elm logs, up to 16 inches in diameter with bark up to 

 1 inch thick, piled in partial shade and left undisturbed until late October, served 

 as a basis with which to compare the results of the several treatments. Percent- 

 ages of control are based on the number of exit holes and unemerged survivors 

 per square foot of bark. 



Merely spreading uninfested logs, up to 19 inches in diameter with bark up to 

 l}4 inches thick, singly in a north-south position in the sun on May 25 and 

 leaving them undisturbed until late October resulted in 63.2 percent control. 

 The upper half of the logs in the sun was free of brood galleries, except for a few 

 almost half way down the sides of the logs (1.9 galleries compared with 7.1 per 

 square foot scattered over the entire upper half of the control logs). On the lower 

 half of the logs the number of brood galleries approximately equaled those in the 

 control logs (15.3 compared with 14.5 per square foot); however, less than half 

 as many exit holes and unemerged survivors were found there (45.7 compared 

 with 94.6 per square foot in the controls). Both in these logs and in the control 

 logs piled in partial shade, brood galleries of Scolytus multistriatus Marsham and 

 Hylurgopinus rufipes (Eich.) were almost equally abundant. 



When logs up to 16 inches in diameter with bark up to 1 inch thick were sim- 

 ilarly placed in the sun on May 25, but turned over on July 12 after the lower 

 portion had become infested, 79.6 percent control resulted. 



Other logs with diameters up to 23 inches and bark up to 1 inch thick were 

 piled in the shade from May 25 to July 12, by which time they were well infested 

 with scolytids. On the latter date they were spread singly in the sun in a north- 

 south position, and on August 2 they were turned over. This resulted in 95 per- 

 cent control. 



When logs up to 24 inches in diameter with bark up to 1 % inches thick were 

 spread singly north and south in the sun on May 25, turned over every week 

 through August 17, and then left undisturbed until late October, 99.7 percent 

 prevention of infestation resulted. Logs up to 23 inches in diameter with bark 

 up to 13^ inches thick, which were turned in the sun every two weeks during the 

 same period showed 98.8 percent prevention, while other logs up to 24 inches in 

 diameter with bark up to 1^ inches thick showed 98.7 percent prevention. 



When logs up to 17 inches in diameter with bark up to J inch thick were spread 

 singly north and south in the sun on May 25 and spraj'ed on the lower half with 

 creosote and kerosene, strained (1 to 4 by volume), over 99.9 percent prevention 

 resulted. 



