Annual aerial survey work last year, although curtailed because of the pandemic, remained sufficient to show that the spruce beetle remains the most damaging forest pest in Colorado for the ninth straight year. The U.S. Forest Service and Colorado State Forest Service last year were forced to prioritize where they did aerial surveys in order to follow COVID-19 safety protocols. That meant they monitored 16.3 million acres from the air, down from 30.2 million acres the year prior, thus preventing comparisons of survey results between 2020 and other years. âDespite the modified flights, observers were able to detect and track pests infesting areas of forests that were previously unaffected, including the spruce beetle and Douglas-fir beetle. While the intensity of these two native bark beetles decreased in 2020, they continue to infest and kill previously unaffected stands,â the agencies said this week in a news release.