BUREAU OF ENTOMOLOGY. 323 



This represents a stumpaije value of $270,000. It is estimated by 

 forest officials and representatives of the Bureau of Entomolo<^y, 

 who are in a position to have intimate knowledge of the subject, that 

 this amount represents the average annual loss during seven years, 

 1912-1919, which would represent a loss of 270,000,000 board feet of 

 merchantable timber with a stumpage value of $2,340,000. During 

 this period, owing to lack of funds, it was possfole for the Forest 

 Service to expend but $00,000 toward the prevention of this great 

 loss of forest resources. Through a completely organ izerl coopera- 

 tive arrangement between the Forest Service and Bureau of Ento- 

 mology, 130,000 acres within the San Joaquin drainage in California, 

 Avith a stand of 1,507,500,000 board feet of yellow pine and 082,500.000 

 board feet of sugar pine, were cov^ered by control work in 1920, and 

 the work of maintaining control will be continued during a period 

 of five years. One of the objects of this project is to make a thorough 

 test of the percentage principle and other methods of control that are 

 recommended by the Bureau of Entomology. An area of 24,000 acres 

 will be left without treatment to serve as a basis of comparison with 

 the treated area. 



The application of the newly-discovered "Craighead solar heat 

 jDrinciple " of insect control, in connection Avith work against the 

 Avestern pine beetle in California, has shoAvn that a maximum daily 

 tem])eratui-e as low as 75° F. during a few clear days Avill kill the 

 broods of beetles in the infested bark removed from the trees and 

 exposed to the direct rays of the sun. This method renders it pos- 

 sible to continue control work during the summer months which 

 heretofore could not be done by the method of burning the bark 

 OAving to fire hazard. 



Extensive reconnaissance and intensive studies are being made in 

 the Coeur d'Alene National Forest of northern Idaho, where, in 1913, 

 over 4,000,000 board feet of merchantable white pine timber Avas 

 killed by the mountain pine beetle. The area to be covered by the 

 in\-estigations is over 348,000 acres, including 80,000 acres of ydloAV 

 pine, with smaller areas amounting to 5,000 acres for the intensive 

 studies. 



The extensive experiments conducted at our field station in southern 

 Arizona during the last five years, to determine the time of year to 

 cut mesquite for fuel and other required local products to aA-oid 

 destruction of the Avood by insects, haA^e been completed and the fact 

 has been demon.strated that if mesquite is cut for cord wood, posts, 

 etc., between October 15 and January 15 in southern Arizona and 

 piled in open ricks, little or no damage Avill be caused by insects. 

 This result is of gi-eat economic importance to the residents of all 

 sections of this and other countries Avhere mesquite furnishes the 

 only or principal .source of fuel and Avood products, because or- 

 dinarily, under the common practice of cutting in the spring and 

 summer months, a very large percentage of the wood is converted 

 into piles of boring dust before the end of the summer. 



The solar heat principle of preventing insect damage to mesquite 

 posts was found to be entirely successful. The posts Avere cut and 

 put out in the sun and turned occasionally until the l)ark was 

 tlioroughlv dried. This kills the in.sects that get in before the bark 



