Hot Topic Forest Health Issues
Mediterranean Oak Borer
The recently detected invasive Mediterranean oak borer (Xyleborus monographus) was found in valley oak in northern Napa Valley. Subsequent detections determined it had established in Middletown (Lake Co.) and eastern Sonoma Co. We are working with US Forest Service, Cal Fire, and CDFA to conduct trapping and research programs.
A Pest Alert will be available soon.
Douglas-fir Branch Dieback
Recently a landowner contacted me regarding branch dieback that was occurring in their planted Douglas-fir. In the last few months, the same symptoms have begun to appear on natural Douglas-fir occurring on the coast.
While I have yet to confirm all the issues in the coastal Douglas-fir, I have found several pests I suspect are causing much of the damage:
These are native insects/diseases and typically are not serious pests. Outbreaks usually occur with favorable environmental conditions and don't cause extensive tree mortality. Management options usually include sanitation and improving vigor. Chemical controls can be used, but are not recommended.
Twig and Branch Dieback of Oaks
This past summer I received multiple calls from land owners and managers regarding branch flagging and dieback on oaks.
The likely cause of these symptoms were several native pests:
Twig canker and oak pit scale
Oak pit scale
A wet and warm spring created ideal conditions for the outbreak of these native pests. Typically they do not result in tree mortality; however, they can present aesthetic concerns. Management usually includes sanitationn and improving tree vigor. Chemical controls are not recommended.
Dieback and Decline of Ornamental Redwood in Lake and Mendocino County
Last summer (2019) I received several calls from Lake and Mendocino County landowners regarding issues with ornamental redwood (Sequoia sempervirens). I have observed two general patterns: trees dying from the top down or declining canopies that appear discolored and drooping. While I have not explicitly determined the cause of the dieback or decline, there are several common health issues that can occur in off-site (i.e. planted outside of their natural range) ornamental redwood. I suspect the issues will persist through this summer.
Forest Health Research
Below are some of the forest health issues were are addressing in our research and outreach Forestry Program, with the goal of helping land owners and managers better understand and manage forestlands in California.
Bishop Pine Forest Decline
Bishop pine forests along the coast of Mendocino and Sonoma Counties are experiencing significant declines due to a multitude of issues (e.g. change in land-use, absence of fire as a disturbance, native and invasive insects and diseases). Working with state and local agencies, researchers, and land managers, we are exploring management options for these unique forest types.
Balsam Woolly Adelgid
Grand fir is an important component of coastal forests in Northern California, the southernmost limit of its distribution. The health of these coastal forests are already impacted by the spread of sudden oak death and bishop pine decline.
BWA infestations were first detected (by FHP and Cal Fire) in grand fir stands along the California coast in 2011. Since then substantial grand fir decline and mortality has occurred in California coastal forests. Therefore, it is important to understand how the health and structure of coastal forests will be impacted by balsam woolly adelgid (BWA).
Sudden Oak Death
We are actively involved in research and outreach with collaborators.
Redwood Forest Health
Redwood are resilient trees, but environmental stressors (e.g. drought) and poor land management can impact these forests.