whereas the bark beetles and bark 

 weevils only burrow in the bark or 

 just under it, but help to introduce 

 the fungi that cause decay or stain- 

 ing. 



After the New England hurricane 

 of September 1938, lumbermen 

 searched in vain for a possible spray 

 material to protect the many fallen 

 trees and unseasoned logs against 

 boring insects. Those logs that 

 could not be sawed into lumber or 

 dumped into ponds before the next 

 spring were ruined by the borers. 

 Since then, however, experiments 

 with new synthetic organic insecti- 

 cides have revealed that benzene 

 hexachloride, a name commonly re- 

 duced to BHC, is effective in pre- 

 venting attack by these insects. 

 Excellent results have been ob- 

 tained with liquid BHC concen- 

 trates diluted in water or in fuel oil. 



BHC is a complex organic chemi- 

 cal composed of several forms called 

 isomers. Only one of the isomers, 

 named the gamma isomer, is effec- 

 tive against insects. The strength 

 of a BHC insecticide is therefore 

 measured by its gamma isomer 

 content. 



Spraying Individual Logs 



In tests, individual pine logs 

 were sprayed on all surfaces until 



they were well soaked and the in- 

 secticide began to run off. The logs, 

 cut the size of cordwood because of 

 convenience in handling, were turned 

 over in the process to achieve com- 

 plete spray coverage. Garden-type 

 sprayers (three-gallon, compressed 

 air) equipped with adjustable spray 

 nozzles were used. Logs cut from 

 live trees during the winter were 

 sprayed only once in the early spring 

 before the insects' flight period. 

 Log surfaces were examined per- 

 iodically during the spring and sum- 

 mer for signs of insect activity, and 

 in the fall and winter the bark was 

 removed to count the insect tunnels. 



Of the materials tested, almost 

 complete protection of pine logs has 

 been obtained with BHC emulsion 

 sprays diluted with water to as 

 little as 0.2 percent gamma isomer 

 content (by volume) and to half 

 that strength (0.1 percent) with a 

 concentrate dissolved in kerosene. 

 The water-diluted spray cost about 

 seven cents a gallon, at late 1951 

 prices. Two gallons, fourteen cents 

 worth, were needed to spray ten 

 logs individually. 



Larger logs, such as those ac- 

 tually used for lumber, should re- 

 quire less spray per board foot of 

 potential lumber, and the use of 

 different spray nozzles may further 



The heap of sawdust is an 

 outward sign of work of the 

 round-headed borers within. 

 The sawdust fell from the 

 hole just above the heap. 



Photo by Robert L. Coffin. 



