- 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.
- The drought is most severe in the southern half of the state while drought conditions in the northern half of the state continue to intensify.
What to expect this summer:
- 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.
Individual Tree Protection Treatments:
Avoiding ineffective and unproven treatments will save time, money and trees. Past drought and bark beetle-caused tree mortality events in California have spurred numerous claims of treatments that protect individual trees from bark beetles. Treatments such as applying worm castings to the trunk, spraying insecticides into bark beetle entrance holes or applying acephate via an encapsulated implant have no scientific support for being effective. Systemic insecticides have shown some promise in limited situations, but they have not proven effective for protecting most conifer species from bark beetle attack. Consult with a forest health specialist before taking any action.
Preventive spraying with certain insecticides has a proven track record for preventing successful bark beetle attack. This type of treatment is most appropriate for protecting pines but can be effective for other trees. Many insecticides used against bark beetles must be applied by a licensed applicator. Insecticides must be applied before trees are infested with beetles. Post-infestation treatments will NOT save your trees. More information is available at: http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprd3839478.pdf
Pheromone repellents have limited applicability. Repellants are available for protecting trees such as lodgepole pine and sugar pine from attacks by mountain pine beetles and for protecting Douglas-fir from attacks by Douglas-fir beetles. Effective pheromone repellants have not yet been developed for other tree and bark beetle combinations.
Please refer to the CDPR website for current product registration at:
Supplemental watering can reduce moisture stress for trees and potentially increase their resistance to bark beetle attacks. Deep watering (a couple of times per month during late spring/early summer) that is focused at the edge of the tree canopy will be most effective. Avoid prolonged and excessive soil moisture around trees during the summer months; as this can lead to other tree health problems. The use of water-efficient irrigation tools such as deep tree watering stakes or root irrigators are highly recommended. Be sure to comply with any local water restrictions.
Removing bark beetle infested trees has shown to be effective in some situations. Prompt removal of infested trees may prevent neighboring trees from being attacked. Trees must be removed before beetles leave the tree to be effective. Bark beetles typically leave a tree about the time needles begin to fade from green to yellow. Bark beetles are no longer in the tree once needles have faded to an orange/red color. Infested tree removal is most effective for Jeffrey pine and lodgepole pine. This treatment is less effective for infested ponderosa pine and white fir.
More detailed information can be found in “Bark Beetles in California Conifers; Are Your Trees Susceptible?” http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5384837.pdf or “Managing Bark Beetles in Urban and Rural Trees” http://calfire.ca.gov/foreststeward/pdf/treenote19.pdf
For assistance, please contact:
CAL FIRE (for State and Private lands)
Cascade and Northern Sierra:
- Don Owen 530. 224.2494
Central and Southern Sierra:
- Tom Smith 916.599.6882
- Chris Lee 707.726.1254
South Coast and Southern California:
- Kim Corella 805.550.8583
US Forest Service (for Federal lands)
- Danny Cluck 530.252.6431
- Beverly Bulaon 209.532.3671 x323
- Cynthia Snyder 530.226.2437
- Tom Coleman 909.382.2871
- Sheri Smith 530.252.6667
USDA is an equal opportunity provider and employer.
CAL FIRE NEWS RELEASE!
California Department of Forestry and Fire Protection
Tuolumne – Calaveras Unit
San Andreas – As drought conditions continue to increase fire danger in the region, CAL FIRE has suspended all burn permits for outdoor open residential burning within the State Responsibility Area of Tuolumne County, Calaveras County, Eastern Stanislaus County and Eastern San Joaquin County. This suspension takes effect June 1, 2015 and bans all residential outdoor burning of landscape debris including branches and leaves.
“As the days get longer, our outdoor activities will increase. Everyone can help reduce the threat of wildfire by remaining extra vigilant of how activities are being done,” said Unit Chief Josh White. Chief White continued, “TCU is staffed and ready for rapid response to serve the community. Working together we can enjoy the summer days ahead.”
“With record-setting drought conditions we must take every step possible to prevent new wildfires from starting,” said Chief Ken Pimlott, CAL FIRE director. “One Less Spark, means One Less Wildfire.”
Similar to last year, CAL FIRE has already responded to significantly more wildfires than average. CAL FIRE is asking residents to ensure that they are prepared for wildfires including maintaining a minimum of 100 feet of Defensible Space around every home.
Here are some tips to help prepare your home and property:
Clear all dead or dying vegetation 100 feet around all structures.
Landscape with fire resistant/drought tolerant plants
Find alternative ways to dispose of landscape debris like chipping or hauling it to a biomass energy facility
The department may issue restricted temporary burning permits if there is an essential reason due to public health, safety. Agriculture, land management, fire training, and other industrial-type burning may proceed if a CAL FIRE official inspects the burn site and issues a special permit.
Campfires within organized campgrounds or on private property that are otherwise permitted will be allowed if the campfire is maintained in such a manner as to prevent its spread to the wildland.
For additional information on preparing for and preventing wildfires visit www.ReadyForWildfire.org.
Calaveras County: 209/754-6600
Tuolumne County: 209/533-5598
San Joaquin and Stanislaus Counties: 877/429-2876
For more information on defensible space and fire safety check out:
CAL FIRE-VIP Program:
Tree Health In A Time Of Drought
The fourth winter in a row of disappointing precipitation has triggered a die off of trees in the Sierra Nevada, most of which is now in ‘exceptional drought’ status. The US Forest Service conducted aerial monitoring surveys in April 2015 and observed a large increase in tree mortality in the Southern Sierra (from Sonora south). Surveyors flew over 4.1 million acres of public and private forest land and found that about 20% had tree mortality on it, totaling over 10 million dead trees.
The Forest Service found severe mortality in many pine species especially ponderosa pine. On private lands along the foothills of the Sierra, surveyors found extensive areas of dead pines. In the Stanislaus National Forest, areas with dead trees doubled since last year. Pine mortality, mostly caused by western pine beetle, was common at lower elevations. Over 5 million trees were killed in the Sierra and Sequoia National Forests, up from the 300,000 trees killed last year in the same area. Conifer mortality was scattered at higher elevation though surveyors note that the survey was conducted too early in the year to detect the full extent of mortality levels.
The insects killing trees in the Sierra are all native insects that are multiplying because of drought conditions. Native insects are a necessary part of the forest ecosystem and speed decay of wood back into nutrients, prey on other insects, and provide food for wildlife. They are normally present at low levels and cause tree mortality only in localized areas.
Drought weakens trees and reduces their ability to withstand insect attacks. Normally, trees use pitch to expel beetles that attempt to burrow into the tree through the bark. Weakened trees cannot produce the pitch needed to repel these beetles, so they are able to enter under the bark and lay eggs. Larvae feed on the tree’s inner bark cutting off the tree’s ability to transport nutrients. Attacking beetles release chemicals called pheromones that attract other beetles until a mass attack overcomes the tree. Many beetles also carry fungi that weaken the tree’s defenses.
Western pine beetle is one of the main culprits killing pines in the Sierra during this drought. It is a bark beetle, one of a genus of beetles named Dendroctonus which literally means ‘tree-killer’. Adult beetles are dark brown and about ¼ inch long. Western pine beetle often attacks in conjunction with other insects.
Other beetles causing tree mortality in the Sierra include mountain pine beetle, red turpentine beetle, Jeffrey pine beetle, engraver beetles (Ips) and fir engravers. Forests with a higher diversity of tree species are typically less affected because beetles often have a preference for specific tree species. Some species may attack only one tree type.
Signs that bark beetles are affecting a tree include pitch tubes (streams or tubes of pitch visible on the trunk), small holes through the bark, or boring dust. If the tree is extremely water-stressed and cannot produce pitch, boring dust may be the only visible sign. Trees with needles that have turned from green to red are dead. Most beetles have emerged by the time trees turn red.
The best defense against bark beetles is to keep trees healthy so they are able fight off insects themselves. Widely spaced trees are typically less susceptible to successful attack by bark beetles since they face less competition for moisture, light, and nutrients compared to densely growing and overcrowded trees. Forest health can be promoted by thinning to reduce overcrowding (so each tree has access to more resources) and removing high risk trees during thinning.
For landscape trees of high value close to a home, watering may be one option to increase tree vigor against bark beetle attacks. Apply about 10 gallons of water for each inch of tree diameter (measured at chest height) around the dripline of the tree once, or several times a month during dry weather.