ANNUAL REPORT, 1943-44 41 



Sprays to Prevent Scolytid Infestation of Individual Elm Logs. (W. B. Becker.) 



Orthodichlorobenzene and Fuel Oil. At Amherst, unseasoned elm logs were thor- 

 oughly sprayed when dry with orthodichlorobenzene and No. 2 fuel oil mixed 

 one to eight b}' volume and applied at the rate of 240 c.c. per square foot of bark. 

 This was done on May 14, five da3's before Hylurgopinus rufipes (Eich.) beetles 

 started to dig their first egg galleries in the vicinity. A small hand-operated 

 compressed air sprayer was used. The crevices where the beetles commonly 

 enter the bark were well saturated, and each log was turned over during the 

 application so all sides could be reached. The sprayed logs together with un- 

 sprayed control logs were then exposed to beetle infestation in the shade. H. 

 rufipes was the only scolytid which attacked the logs. Compared with unsprayed 

 control logs of similar size, 99.5 percent prevention of H. rufipes infestation per 

 square foot of bark was obtained, based on the number of brood galleries which 

 became established in the logs. Based on the number of progeny which emerged 

 from the bark during the season (beetle exit holes), 100 percent prevention was 

 obtained; and based on the combined number of progeny which emerged and 

 which were still present in November, 98.5 percent prevention was obtained by 

 spraying. 



Creosote and Kerosene {strained). Unseasoned elm logs were thoroughly 

 sprayed with creosote and kerosene mixed one to four by volume and applied 

 at the rate of 160 c.c. per square foot. This was done on May 20, one day after 

 H. rufipes beetles started to dig their first egg galleries in the vicinity. Complete 

 prevention of all H. rufipes infestation was obtained for the entire season. When 

 this spray was applied to parts of other logs which were also subsequently piled 

 in the shade, the unsprayed portions were infested with H. rufipes. 



These results suggest that, under these conditions, thoroughly coating the 

 entire bark surface with either of these two spray mixtures just before the beetles 

 lay eggs in the spring may be expected to prevent H. rufipes infestation to a 

 great extent for the entire season. If the entire bark surface is not thoroughly 

 covered with a sufficient amount of spraj' material, the scolytids may infest the 

 unsprayed portions. Since the beetles commonly dig into the bark at crevices, 

 the spray must penetrate into all such places. 



The large elm borer, Saperda tridentata Oliv., was also apparently repelled by 

 both of these spray mixtures, but was abundant in the unspra\ ed logs. 



While neither oT these spray mixtures is pleasant to work with, the creosote- 

 containing spray is much more disagreeable to handle. When the creosote is 

 mixed with kerosene, a black precipitate is produced which must be removed 

 before the liquid is poured into the spray tank. The fire hazard must also be 

 taken into consideration with sprays of the type used in these experiments. How- 

 ever, these materials may prove useful in preventing infestation of logs thrown 

 on town dumps and other locations where the fire hazard and injury to adjoining 

 vegetation may not be a problem. 



Sprays to Kill Scolytids Breeding in Individual Elm Logs. (W. B. Becker.) 

 Orthodichlorobenzene and Fuel Oil. At Westfield,^ scolytid-infested elm logs were 

 thoroughly sprayed during July 1942 with the orthodichlorobenzene-fuel oil 

 mixture described in the previous section, at the rate of 52.5 c.c. per square foot 

 of bark. Both H. rufipes and S. multistriatus brood galleries with only immature 

 progeny were in the logs at the time of spraying. None had emerged. After 

 the spray application the spraj-ed logs, together with unspraj-ed control logs, 

 were piled in partial shade. Compared with unsprayed logs of similar size, 79 



' Mr. W. E. Marshman, the Westfield tree warden, kindly provided the logs for this experi- 

 ment and a place where the work could be carried on. 



