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June 6, 2016
Vol. 3, Issue 3
June 2016
Save the Date!    

June 16 -  Invasive Tree Pests for Parks Managers Workshop; King Gillette Ranch, Calabasas, CA

June 21 - 23
- Sixth Sudden Oak Death Science Symposium: Biosecurity, Plant Trade, and Native Habitats; Fort Mason, San Francisco, CA

June 29 - CFPC 2016 Insect and Disease Field Tour, Klamath National Forest, Happy Camp, CA

September 13-15
-
Coast Redwood Forest Symposium: Past Successes and Future Directions; Sequoia Conference Center, Eureka, CA
What Happened to that Tree? 
When a tree dies, people want to know why. Sometimes the answer isn't
Dying bishop pines. By Chris Lee, Cal Fire 
straightforward; combinations of pests often work together to take advantage of stressed trees.
 
Some of these associations are well-known, such as the one between bark beetles and vascular wilt fungi. Bark beetles carry sticky fungal spores into a tree as they penetrate it and tunnel within the inner bark. The spores germinate inside the beetles' galleries and form fruiting structures that protrude into the galleries so that young beetles pick them up before emerging to fly to a new tree, which they in turn inoculate with the fungus. In such a relationship, both species benefit - the fungi are transported to new host material and the beetles get help from the fungi to overcome a tree's defenses.
 
A less clear-cut relationship is that of bark beetles and root pathogens.
Red turpentine beetle pitch tube. By Chris Lee, Cal Fire 
  When bark beetles decimate a conifer stand, it is easy to blame them as the sole mortality agent. Yet, trees that are t argeted by beetles are often already infected and wea kened by root pathogens, making them more attractive to bee tles. Many of the trees currently dying in the Sierra Nevada, Transverse Ranges, Coast Ranges, and Klamath Mountains were   predisposed to beetle attack because of root pathogens such as Heterobasidion root disease.
 
An example of complex tree mortality can be seen in the photo of the
Leptographium stain. By Chris Lee, Cal Fire
failing bishop pines. The trees had thinning crowns symptomatic of root disease as well as entrance holes and pitch tubes, signs of beetle attack. Closer examination revealed red turpentine beetle larvae in the base of the tree and staining of the xylem tissue that yielded a species of Leptographium, a common blue-stain fungus of conifers in California that blocks the transport of water in the tree. Around several larger neighboring pines that had previously been cut were the fruiting bodies of the root decay fungus commonly called the "velvet-top fungus." The property owner had also recently built a small utility building very close to the trees and surrounded it with heavy gravel fill. This construction likely disturbed the trees' root systems, which intensified pre-existing root infections, further stressed the trees, and encouraged the buildup of beetle populations that introduced the Leptographium.
2015 California Forest Pest Conditions
The cumulative effect of California's fourth year of the drought, overstocked forests, and higher than average temperatures led to the die off of nearly 28 million dead trees in 2015. Statewide, 8,380 fires (state and federal responsibility areas) consumed 846,872 acres, killing millions of trees outright, while leaving millions more weakened and susceptible to insect and disease attacks. Drought-stricken and fire-damaged trees fueled bark beetle outbreaks of epidemic proportions, and oak and incense cedar died outright from drought. For more information on California's USDA Forest Service aerial surveys, insect conditions, forest diseases and abiotic conditions, and invasive plants for 2015, see the 2015 California Forest Pest Conditions report.
Newsletter feedback and ideas are welcome.  Please submit comments to caforestpestcouncil@gmail.com

When buying firewood for home heating or camping, remember to buy it from local sources, helping to minimize the spread of pests and diseases - Buy It Where You Burn It.  For a list of firewood dealers local to where you live, go to firewoodscout.org.

Sincerely,

Katie Harrell
Communications Director  
California Forest Pest Council
California Forest Pest Council | (510) 847-5482 | caforestpestcouncil@gmail.com |

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