The Douglas-fir Tussock Moth is a native defoliator of California's forests. Outbreaks occur periodically and the last one near Buck Lake in the Plumas National Forest was in 2013-2014. This current outbreak began in 2022 and strengthened in 2023. Remote sensing using HiForm and 10m Sentinel-2 gives us the ability to precisely track defoliation over multiples years. In some cases repeated defoliation can lead to tree mortality, and that too  can be captured by remote sensing monitoring.