. Cooperative economic insect report. Insect pests Control United States Periodicals. - 1010 - also occurred on some 150,000 acres in parts of Shasta and Lassen Counties. In southern California, many Coulter pines were killed at several locations; in River- side County, groups of 90 or more trees were killed late in the season. In some places outbreaks were sparked by forest fires where beetle broods de- veloped in scorched trees; in others they developed in trees struck by lightning. Warm, dry weather during winter and early spring favored bettle broods in all areas. Mountain Pine Beetle Infe
. Cooperative economic insect report. Insect pests Control United States Periodicals. - 1010 - also occurred on some 150,000 acres in parts of Shasta and Lassen Counties. In southern California, many Coulter pines were killed at several locations; in River- side County, groups of 90 or more trees were killed late in the season. In some places outbreaks were sparked by forest fires where beetle broods de- veloped in scorched trees; in others they developed in trees struck by lightning. Warm, dry weather during winter and early spring favored bettle broods in all areas. Mountain Pine Beetle Infestations Most Abundant In Decade Infestations of the mountain pine beetle, Dendroctonus monticolae Hopk., in sugar pine were more numerous and widespread than at any time in the past 10years. The beetles killed more lodgepole pine in many stands, and began new infestations in pole-size stands of ponderosa pine in Modoc County. The most critical outbreaks in sugar pine were in the southern part of the westside Sierra in Calaveras, Mariposa, Madera, and Tuolumne Counties. In some places, trees of all ages were killed in groups. Mortality over large areas averaged one or more pines per quarter section. Several widespread outbreaks of lesser intensity also occurred in the northern part of the westside Sierra. Infestations covered several thousand acres in both Shasta and Yuba Counties. In YoSem- ite National Park, and in the adjacent Mather-Crane Creek drainages, losses are the highest in several years. Infestations in lodgepole pine increased but became critical in only a few areas. The outbreak in the Dingley-Delaney Creek drainages near Tuolumne Meadows, Yosem- ite National Park doubled that of 1958, and a new loss center developed in the vicinity of Cathedral Lake where stands had been weakened by needle miner defoliation. Other centers of severe infestations in lodgepole pine occurred at Lassen Volcanic National Park, Las sen County; on the Plumas National Forest in Plumas Cou
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