Learn what you can do about drought-stressed trees and bark beetles

Current Situation

Four years of drought have put tremendous stress on trees in California’s forests, resulting in widespread mortality. Bark beetles are the primary cause of mortality for most pine and fir trees but other trees such as incense cedar and live oak are simply dying from lack of water. Extensive tree mortality is occurring in many areas across federal, state and private lands.

What to expect this summerÔā∑

Extreme drought will put additional pressure on already stressed trees, leading to new and expanding mortality. Bark beetle populations will continue to increase, expanding and intensifying in current outbreak areas and reaching outbreak levels in new areas. While drought may impact most trees, expect some of the greatest impacts on ponderosa, Jeffrey, lodgepole and sugar pines, as well as white fir and incense cedar. In southern California, also expect significant mortality of Coulter, bishop and Monterey pines, as well as oak trees growing on drier sites.

What you can do to protect your trees

Improve tree growing conditions - this is typically accomplished through selective tree removal (thinning) to reduce inter-tree competition for limited water and nutrients. The best time to thin is during non-drought periods.

Inspect your trees - know what tree species you have and identify individuals that are most susceptible to drought and bark beetles; look for signs and symptoms of attack such as pitch tubes (globs of resin) and boring dust (sawdust) on the trunk. Also identify trees for removal that may be hazardous to life or property.

Protect high-value trees - Extreme drought conditions in many areas of the state have necessitated that landowners and managers consider ways to protect individual trees in high-use and residential settings. Individual tree treatments such as preventive spraying with insecticides, the use of synthetic products that repel bark beetles, supplemental watering and prompt removal/disposal of infested trees may all be effective depending on the situation and the tree species at risk. It is important to consult with a forest health specialist to determine the best treatments for your trees as there are several factors to consider and pros and cons to every treatment.

Learn more about what you can do to protect trees by following the link to this flyer