No snow: Bark beetle threat increases

Publisher’s note: This is one of a series of blurbs about how the lack of winter is impacting the Lake Tahoe Basin. If you have an idea, please email it to info@LakeTahoeNews.net.

More dry weather is likely to mean more bark beetles destroying pine trees in the Sierra.

“There typically is a one- to two-year lag between when drought starts and when we start seeing increased bark beetle activity. While beetle activity started to increase in 2013, aerial surveys still recorded a fairly normal amount of tree mortality,” CalFire said in a statement. “There was significant mortality in certain areas, but overall mortality was not high. In contrast, tree mortality in 2014 is likely to be much higher. When the drought does end, there too will be a lag time before beetle activity dies down.”

California’s driest year on record was 2013, as well as the second consecutive year of below normal precipitation for the state. Without adequate precipitation, trees do not have enough water for normal growth and may be severely drought stressed by the end of the summer. For pines, true firs and some other conifers, bark beetles are the pest that typically kills drought-stressed trees. As bark beetle numbers increase, tree mortality increases. By the end of 2013 there was clear evidence that bark beetle numbers were increasing.

For individual, high value trees, supplemental watering and application of pesticide sprays (registered for use on pines) to prevent bark beetle attack are viable options and have been met with limited success, according to CalFire. For trees in forest stands and plantations, these treatments are not practical

— Lake Tahoe News staff report