42 MASS. EXPERIMENT STATION BULLETIN 417 



percent mortality occurred in the sprayed logs, based on the number of surviving 

 progeny (immature and emerged) of both species per brood gallery the next 

 spring. Many Saperda tridentata Oliv. and some Magdalis sp. survived the spraj' 

 application. 



While 79 percent mortality is a considerable reduction, it would still allow 

 more beetles to survive than is desirable in the case of a vector of a disease. 



Creosote and Kerosene. Attempts to kill scolytids in elm logs by spraying the 

 entire bark surface with 12.2 c.c. per square foot of the creosote-kerosene mixture 

 dscribed in the previous section were not at all successful. A heavier application 

 might be more successful. 



The Prevention of Hylurgopinus rufipes (Eich.) Attack by Repeatedly Turn- 

 ing Unseasoned Elm Logs in the Sun during the Early Season Oviposition Period. 



(W. B. Becker.) Freshly cut elm logs lying in a north-south direction in the 

 sun at Amherst were rolled 180 degrees of their circumference (1) every week 

 and (2) ever}' second week during the early-season oviposition period of H. 

 rufipes (May 19 to July 2 in 1943). Many egg galleries were started on the lower 

 halves, but when the logs were turned so that the sun heated the bark above the 

 temperature which the beetles could tolerate, development in almost all cases 

 stopped. Relatively few egg galleries reached the stage where eggs were laid 

 in them — fewer in the logs turned every week than in those turned every second 

 week. Of those larvae which developed from these eggs, most died when still 

 very small. No attacks occurred after July 2, which was the last date the logs 

 were turned. On one large log which was left in the sun unturned from May to 

 November, the upper half was not suitable for the construction of egg galleries, 

 while the lower half was. In comparison with control logs piled in the shade, 

 logs turned over at one-week intervals were practicall}' free from infestation, both 

 on the basis of the number of beetles, per square foot of bark, which had emerged 

 by the end of the season (November) and on the basis of the combined number 

 of emerged progeny and immature progeny still in the bark at the end of the 

 season. The control was practically as good where logs were turned at two- week 

 intervals. When the logs were examined in November, none seemed to be in a 

 condition which would be suitable for further attack the next spring. 



The successful results obtained in this experiment suggest that, in certain 

 situations, this method might prove useful in preventing an increase in the local 

 beetle population. Of course, warm sunny weather is necessary. However, since 

 experiments were started here in 1939, solar-produced heat has always prevented 

 elm bark scolytids from becoming established in all or most of the upper half of 

 elm logs exposed to the sun since spring. 



Combined Use of Sprays and Solar Heat on Individual Elm Logs. (W. B. 



Becker.) Individual unseasoned elm logs laid in a north-south position in the 

 sun at Amherst on July 2, 1943, were sprayed on the top half with (1) the ortho- 

 dichlorobenzene-fuel oil mixture and (2) the creosote-kerosene mixture previously 

 described and then rolled over so the sprayed half was underneath. Unfortu- 

 nately, not enough H. rufipes beetles attacked even the control logs to furnish 

 any comparative data. However, since attacks on entire individual logs in the 

 shade have been prevented by spraying, and attacks on most of the upper half 

 of untreated logs have been prevented by laying them in the sun, it seems possi- 

 ble that (1) laying logs to be sprayed in the sun may save much spray material 

 since only slightly more than half of the bark area on each log need be sprayed, 

 and (2) spraying the under half of logs in the sun may save returning at a future 

 date to turn them over. 



