L.A. County Arboretum & Botanic Garden Plant Info: January 2013

I helped out at the “New Oak Threats Workshop” today at the Huntington. This was an outreach program for tree professionals and the general public to alert them to the spread of the Polyphagous Shot Hole Borer and what steps they can take to help stop or slow down the spread of this potentially massive threat to both native and ornamental trees here. Much of the information about this pest can be found here on Dr. Akif Eskalan’s lab page, but some important new information was revealed at this seminar. Here’s my summary of what that is:

-Chipping infested wood, solarizing it and leaving it on site under a sealed tarp or composting the chips is the best way to prevent the beetle from re-emerging from cut wood and infesting new trees or re-infesting already infested trees and increasing the level of damage to the trees.

-Several insecticides have been tried on the chipped wood and two common ones have proven effective (at preventing beetles from emerging from the chipped wood; trials on trees are not finished).

-This infestation is so large and potentially devastating that Dr. Akif’s lab is reaching out to tree professionals, horticultural professionals, and governmental departments that deal with trees for help in identifying possible infestations.

-California State University San Bernardino is hosting a web application that can be opened up in your smartphone to report suspected shot hole borer or suspected gold spotted oak borer occurances. The app uses your phones gps to report on the location of the damage. If you want to be part of the team that can help deal with these threats to our oaks and other plants, both native or non-native, just cut and paste this link: (http://wrimedia.csusb.edu/oaktree/mobileapp/survey.php ) into an email to yourself and open it up in your smartphone.

-The number of tree species affected by the borer is growing; over 200 trees are known to be attacked by the borer, and the list of reproductive hosts, i.e. hosts that are not only attacked by the borer but help to spread the infestation, has grown. The reproductive host list now includes 22 species and will probably increase (California native plants are in red type):

· Box elder (Acer negundo)

· Castor bean (Ricinus communis)

· Avocado (Persea americana)

· English oak (Quescus robur)

· Coast live oak (Quercus agrifolia)

· California Sycamore (Platanus racemosa)

· Big leaf maple (Acer macrophyllum)

· Mimosa (Albizia julibrissin)

· American sweet gum (Liquidambar styraciflua

· Silk Tree (Albizia julibrissin)

· Coral tree (Erythrina corallodendon

· Titoki (Alectryon excelsus)