146 MISC. PUBLICATION 273, U.S. DEPT. OF AGRICULTURE 



Since outbreaks in standing, healthy trees are sporadic and of 

 short duration, the destruction of the broods in these trees, 

 through the application of control methods, seldom contributes a 

 great deal toward reducing the damage. Efforts should be directed 

 toward preventing outbreaks by eliminating all situations favor- 

 able to the development of excessive progeny. Thus, slash should 

 he piled and burned before the Ips beetles emerge, or should be 

 scattered in the open where the sun will dry it out and make it 

 unsuitable as a breeding medium. If it should be necessary to 

 destroy broods in standing trees, the most economical and effective 

 method is to fell the trees and burn or scorch the infested bark. 

 A large number of species of this genus are recorded from western 

 pines, all very similar in appearance and habits, so only a few of 

 the more common species need be mentioned here. 



The western six-spined engraver (Ips ponderosae Sw.) is a sec- 

 ondary enemy of ponderosa and digger pines. For the most part 

 it attacks trees that have been felled or those dying from attacks 

 of more primary species of bark beetles. The adults are about 1/ 4 

 inch long, reddish brown to black, with six spines on each side of 

 the elytral declivity. The gallery pattern consists of two to five 

 egg galleries extending up and down the tree from the central 

 nuptial chamber. Though the pattern is similar to that of /. ore- 

 goni, the galleries are distinctly wider. This beetle has been re- 

 corded from Arizona, California, Montana, South Dakota, and 

 Colorado, and undoubtedly is present in other Western States. 



The California five-spined engraver (Ips confusas (Lee.)) (fig. 

 66) is destructive to saplings, poles, young trees up to 30 inches 

 in diameter (breast high) , and the tops of mature trees. It com- 

 monly attacks ponderosa, sugar, western white, Coulter, digger, 

 and Monterey pines, and, less frequently, other pines in California 

 and southern Oregon west of the Cascade and Sierra Nevada 

 ranges. It breeds readily in slash and felled logs, and the broods 

 developed in such material often cause extensive damage to the 

 young pine growth in the vicinity. 



The adults are reddish brown to pitch black, about 3 / 16 to % 

 inch long, and have five spines on the margin of each side of the 

 elytral declivity. The egg galleries usually comprise from three to 

 five nearly straight tunnels radiating from a central entrance 

 chamber. The typical form has three galleries in the shape of an 

 inverted Y. The galleries are not packed with boring dust and are 

 usually from 5 to 10 inches long. Attacks are started early in the 

 spring and from two to five generations of beetles may develop 

 during the summer. In the northern part of the range, at an eleva- 

 tion of about 3,000 feet, there are usually two summer generations 

 which develop in fallen logs and a third, or overwintering genera- 

 tion, which develops in standing trees. At lower altitudes and in 

 the southern part of the range there are from three to five summer 

 generations. Most of the beetles overwinter in the adult stage, un- 

 der the bark of recently killed trees. 



Some attempts have been made in California to control out- 

 breaks of this beetle in young pine stands by felling the trees and 

 burning the infested bark during the winter and early spring 



