Waiting to cut tree allows pest to spread to healthy trees

Community protection and financial aid may be a conflict that is yielding the proverbial “unanticipated results,” opined Gregg Bratcher, Cal Fire’s division chief for forestry on the Hill.

Although the number of oaks infested with the Goldspotted oak borer continues to increase on the Hill, Bratcher is concerned that residents are deferring or delaying the removal or protection of these infested trees until they obtain a grant from the Mountain Communities Fire Safe Council.

Edwina Scott, MCFSC executive director, confirmed, “We are getting the same response from homeowners. We do not have funds to remove GSOB trees. Our dead and dying tree removal grant is based on the Governors Emergency Proclamation for bark beetle trees.”

An infested tree cannot be saved. The larvae have had time to feed on the tree’s cambium layer, which eventually interferes with the movement of nutrients from the roots to the leaves. But healthy trees can be protected with appropriately applied pesticides, according to Bratcher.

“Spraying is [needed] for spring time just before flight season after the spring moisture. Generally done around April,” Bratcher urged. But some property owners want to wait until late summer or fall before taking action. They seem “unwilling or unable to take preventive maintenance,” he thought.

This delay allows the GSOB time to evolve from its larval stage, exit the oak and take flight through the neighborhood and community, landing on and attacking healthy oaks. Consequently, even if the infested tree is eventually cut, the infestation has had an opportunity to spread.

Bratcher, who has observed this behavior and discussed it with local arborists, shared his thoughts after the recent Mountain Area Safety Task Force meeting last week.

John Huddleston of Precision Tree Experts says arborists have three different methods to help the oaks. “There are barriers, partial systemics and total systemics,” he wrote in an email.

He summarized each strategy: “The barrier strategy is a compound called bifenthrin. It is an extremely common insecticide found in many common products.

“The partial systemic strategy is a compound called dinotefuran. When mixed with a penetrating surfactant, it can be applied directly to the bark and will travel into the leaves. Adult GSOB beetles are poisoned when they eat the leaves. It does not affect any larvae that are feeding in the phloem. It needs to applied in April, and will break down in about three months.

“The full systemic strategy is a compound called emamectin benzoate. It is injected directly into the tree’s xylem by drilling holes into the root flare. It will affect the adults that feed on the leaves, as well as the larvae feeding in the phloem.”

Money and cost are not the only concern property owners have, according to Huddleston. The effect on honey bees is frequently mentioned, but “California requires that every pesticide of these classes have information in the label regarding that product’s specific threat to bees,” he said.

Applicators must have a license from the state and county. Any questions about the status, licensing and registration of any of the listed or non-listed companies should be directed to the Riverside Agricultural Commissioner’s Office at 951-955-3045.

A list of operators in Riverside County can be found at http://ucanr.edu/sites/gsobinfo/Resources/By_County/Riverside_County/Licensed_Pest_Control_Operators-Riverside_County/ and to verify a license one can visit www2.cslb.ca.gov/OnlineServices/CheckLicenseII/CheckLicense.aspx.

The GSOB hotline remains 951-659-8328. He urged residents to call if they fear a local oak has been infested with GSOB.

“We need to collaborate. Everyone on the Hill is affected by the GSOB,” he lamented.

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