Many have noticed discoloration of lodgepole pine forests in the greater Tuolumne Meadows area. This is due to a tiny moth called the lodgepole needle miner. The larvae live inside pine needles, eating them from the inside out, and only emerging in the late summer as small gray moths for a few weeks in the late summer of odd-numbered years. The lodgepole needle miner has few effective natural predators, as not many creatures can make a good living eating something that’s only out a few weeks every other year. Repeated defoliation slowly starves trees, and makes them vulnerable to mountain pine beetle colonization. Needle miner populations generally keep rising until the overstory trees in an infested area die, then start building slowly again. Historically, large areas of lodgepole overstory die and leave isolated California red fir or mountain hemlock exposed to snow damage and wind throw. Approximately 50,000 acres of defoliation was mapped last year, and this is the fourth major episode since 1900. (NPS)
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