- Editor: Jennifer Hopkins
Invasive Spotlight: Goldspotted Oak Borer (GSOB)
Adult goldspotted oak borer, Agrilus auroguttatus, on an oak leaf. Photo by Mike Lewis, Center for Invasive Species Research, Bugwood.org
There are several flatheaded boring beetles in California, however only a few are of particular concern. The goldspotted oak borer (GSOB), Agrilus auroguttatus, is a metallic wood-boring beetle that threatens our native trees. Since it was introduced to Southern California on contaminated firewood in the early 2000s, this pest has caused extensive damage to woodlands and native oaks.
What does the goldspotted oak borer look like?
Adult GSOB are 0.4 inch long and 0.08 inch wide with bullet-shaped bodies. They are black with an iridescent green sheen and six distinct gold spots on their back.
What damage does the goldspotted oak borer cause?
Goldspotted oak borers only attack oaks (Quercus spp.). They are particularly damaging to coast live oak and California black oak. Adult beetles lay eggs on host trees and the larvae bore into the wood, feeding on the tree's vascular tissue. The larvae feed on the tree until they pupate into adults and exit the tree, leaving D-shaped exit holes in the bark. Extensive GSOB feeding can girdle trees, disrupting water and nutrient uptake and eventually causing the tree to die.
What can you do about the goldspotted oak borer?
Don't move firewood! The most important way to prevent the spread of invasive wood borers like GSOB, is to buy firewood where you're going to burn it. If you live in an area of Southern California where GSOB is present, avoid planting susceptible trees. If you need to remove an infested tree, keep the cut wood away from healthy oaks and tarp or grind the wood to kill any larvae present. To report possible sightings, fill out the Goldspotted Oak Borer Symptoms Reporting Form at https://ucanr.edu/sites/gsobinfo/What_You_Can_Do/Report_GSOB_Symptoms/
To learn more about this invasive pest visit the UC IPM Pest Notes: Goldspotted Oak Borer or the UC ANR Goldspotted Oak Borer page.
- Author: Tami Reece
I have caterpillars eating the leaves on my oak trees, what should I do?
Ann M. Arroyo Grande
The California oakworm is probably your pest. On a typical year, there may only be two generations of oakworms, but this year was unusually warm and dry in mid-winter, which has created a perfect environment in order to have a third generation. The life cycle of an oak moth starts with eggs, then maturing to a larva (caterpillar), eventually transforming into a chrysalis (pupa) then finally to the adult oak moth. The oakworm is a small light green caterpillar with a dark brown head and dark stripes on their sides. The oak moth may be spotted during the summer afternoons.
The California oakworm’s favorite food of choice is the coast live oak. Populations are unpredictable year to year, with outbreaks appearing occasionally followed by years of almost no damage to oak trees at all. Don't panic, healthy oaks will tolerate extensive loss of leaves without serious harm, so treatment to control oakworms usually is not recommended. In the past month, the Master Gardener helplines have received numerous reports that there is an abundance of oakworms in San Luis Obispo County. Pesticide sprays applied to control oakworms usually are not warranted to protect the health or survival of oak trees. If you believe your oak trees need protection because they are stressed, regularly check foliage for oakworms and spray least toxic pesticides only when caterpillars reach levels needing treatments. Control oakworm and protect oaks with an integrated pest management (IPM) program that relies primarily on the conservation of natural enemies and good cultural practices. Yellowjackets and garden spiders are good predators of oakworms. Providing a birdbath may help increase the amount of birds in your yard, which will help decrease numbers as well. A good resource for identifying and controlling the oakworms through the use of natural enemies is http:www.ipm.ucdavis.edu.
If you feel that your oak tree was weak or dying before the oakworm outbreak, you may want to consider the cultural care of your tree. Oaks do not need irrigation, unless supplementing during a time of winter drought. Is your tree affected by nearby lawns, compacted soil, damaged roots from construction or nearby pavement? UC ANR offers a free download of their publication "Living Among The Oaks" a guide to keeping your oak trees healthy so they can benefit generations to come.
- Posted By: Amy Breschini
- Written by: Ann Dozier
Turf’s up
By Ann Dozier
Q: At the end of summer are you unhappy about the amount of work and water your lawn requires? Or, are you wondering what will fill your vegetable bed when the squash vines are ripped out?
A: No, we’re not recommending that you tear up your lawn and plant vegetables, although that might be a solution for problem lawns. Instead, come to the Master Gardener Advice to Grow by presentation Saturday, September 17, to get some answers to both questions.
The session will offer a seminar on turf replacement plants featured in the demonstration at the Garden of the Seven Sisters. Gardeners hoping for sustainable ground covers will learn about eight different kinds of ground covers/grasses that take little water or mowing and are disease resistant and amenable to foot traffic. And they look good, too!
The ground covers are planted in 3 different blocks, which will all be on three different irrigation schedules in the future. These grasses may be mowed to resemble lawn or left unmown for easy care. Four of these turf replacements are native to California and four are chosen from other Mediterranean climate areas. All provide attractive alternatives to a conventional lawn. Fall is the best time to plant these new ground covers.
As your vegetable garden winds down summer production you may wonder what vegetables you should plant next – or perhaps you’re planning a season of rest and wonder how to put the vegetable garden to bed for the winter. Another section of Saturday’s presentation will focus on vegetables, showing what winter veggies can be started or planted now. It will also describe the list of chores for fall in the vegetable garden.
The free Advice to Grow By presentations are held from 10-12 at 2156 Sierra Way in San Luis Obispo. Come prepared for changeable weather and bring a chair if possible.
Click here: For more information about the garden turf alternatives.
Got a Gardening Question?
Contact the University of California Cooperative Extension Master Gardeners: at 781-5939 from 1 to 5 p.m. on Monday and Thursday; at 473-7190 from 10 a.m. to noon on Wednesdays in Arroyo Grande; and at 434-4105 from 9 a.m. to noon on Wednesday in Templeton. Visit the UCCE Master Gardeners Web site at groups.ucanr.org/slomg/ or e-mail mgsanluisobispo@ucdavis.edu
