Project Photos & Videos

Dec. 29, 2011 -- Healthier forests will provide more products, services, and benefits to local communities. Fewer dead trees will reduce the amount of available fuel and lessen the risk of uncontrollable wildfire and its impacts on nearby communities.

Forest Service Recovery act hires in this project are field-testing alternative approaches to reduce tree mortality from a combination of sudden oak death caused by Phytophthora ramorum and insect attacks. If found to be effective, this technology may provide land managers with a new method for mitigating excessive tree mortality from these organisms. (left) A bleeding canker on a coast live oak stem infected with P. ramorum.

 This project was initiated in late spring 2010 with a search for and selection of suitable study sites in the vicinity of Novato, California. (right) Coast live oak killed by P. ramorum (causal agent for sudden oak death) near Novato.

So far, results from this work have shown that sapwood from within P. ramorum cankers on stems of coast live oak trees contain much higher concentrations of ethanol than adjacent healthy sapwood outside the canker, or compared to sapwood from nearby healthy trees.

(left) The yellow line marks the boundary of a P. ramorum canker on the stem of a coast live oak. Arrows point to small gallery entrance holes of bark or ambrosia beetles attacking the canker. The silver nails mark where tissue samples were removed with an increment borer.

 The research also demonstrated that traps baited with ethanol lures attract species of bark and ambrosia beetles known to selectively attack inside the boundaries of the P. ramorum cankers and subsequently reduce the trees’ probability of survival. These same beetle species were shown to attack coast live oak logs when sealed holes in their sapwood were filled with ethanol solution. (right) Maia Beh setting up an insect trap with an ethanol lure. 
 

The researchers concluded that ethanol associated with P. ramorum cankers is the primary attractant and attack stimulant for the bark and ambrosia beetles that colonize the cankers and accelerate tree death. Others have reported that preventing beetle attacks could extend the trees’ survival by five to nine years.

The trapping experiment described above found that adding either α-pinene or 4-allylanisol to traps baited with ethanol lures greatly reduced the trap catch, indicating that these compounds are repellents. The α-pinene also dramatically reduced beetle attacks on the coast live oak logs with ethanol infused sapwood provided the α-pinene release rate was high enough. This project continues through 2012.