Bark Beetles
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Mountain Pine Beetle p.58 |
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Dendroctonus ponderosae Hopkins |
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Hosts-- Most native and introduced species of pines, except Jeffrey pine.
Distribution-- Wherever host species are found.
Damage-- Both adults and larvae feed in phloem layer of inner bark. Sapwood may be lightly scored. Feeding girdles the tree. Tree is inoculated with blue stain fungi clogging water transport system. Usually trees are killed, but some may be strip attacked. Trees less than 5 inches d.b.h. are seldom attacked. Large outbreaks of this beetle are common, especially in lodgepole pine.
Identification-- This is one of the few bark beetles that usually make very obvious pitch tubes on bark surface at site of attack (fig. 73). Pitch tubes are masses of red, amorphous resin mixed with bark and wood borings. Boring dust is evident in bark crevices and around base of infested trees.
Under bark, look for straight, vertical egg galleries with crook or "J" at start (fig. 72) which can extend upward 30 inches or more. Galleries are packed tightly with boring dust. Larvae (grubs) are present during fall and winter (fig. 94a). Most pupate in late spring and adults emerge from the bark in midsummer to attack new trees. Mature adults are black and about three-sixteenths inch long. Infested trees fade within a year from yellow-green to red-brown. Thin-bark hosts (primarily lodgepole pine) may have their bark removed by woodpeckers searching for larvae.
Similar damage-- Boring dust is present with attacks by Ips species or other secondary bark beetles. Gallery pattern distinguishes mountain pine beetle. Jeffrey pine beetle is similar but occurs only in Jeffrey pine.
Bark Beetles
Western Balsam Bark Beetle Figure 92 / Bark beetle gallery patterns. Figure 93 / Adult bark beetles. Figure 94 / Bark beetle and borer larvae.
Figure 72. Mountain pine beetle gallery has a "crook" at the lower end.
