While this Green Valley oak was being scrutinized in 2015, other oaks in the area had gone into a quick decline, were partially dead or had died from the Goldspotted Oak Borer (GSOB). We often see a GSOB-infected oak “die suddenly” but GSOB has probably been in that tree 6 months or more. The tree continues to pull water and nutrients between the infested areas. Eventually, the insect girdles the tree and shuts down all the water and nutrients to the tree. GSOB begins at the top/canopy of a tree and works its way down the tree. This is why it is important to identify a thinning tree canopy. There is one cycle of GSOB per year. Adults fly from mid-May to early October with peak flight occurring late-June to early July. Adults feed on the oak foliage. Females lay eggs in crevices in the bark of the main stem and larger branches. The eggs develop into larvae and bore through the bark into the phloem. They feed inside the tree from July to mid-December. The specific D-shaped emergence holes are created by the adults when they leave the tree.
How was GSOB discovered here:
This particular oak was identified by a very alert Southern California Edison employee. His expertise was to check trees near power lines for trimming but he had been trained to look for GSOB since taking infected wood out of the valley was known to spread GSOB. This tree was not near power lines but he was also on the lookout for any sign of GSOB infection. He alerted LA County Fire/Forestry and US Forestry. A bark sample was taken to a lab which confirmed that GSOB was in Green Valley.
About The Green Valley Oak Tree Alliance
The Green Valley Oak Tree Alliance was formed in 2020 by a group of Green Valley residents. LA County Forestry/Fire had already taken down 700 infected oaks here in Green Valley. The sound of chainsaws and chipper was overwhelming and our beautiful valley was beginning to look very different. The owners of the above tree had begun using injections for their other trees in 2016. All five of those lightly-infected oaks are alive today. Our GVOTA was formed to research and share the alternatives to cutting down a classic oak. We learned to do our own oak injections. We planned a community injection workshop last spring as well as this spring. The pandemic forced us to cancel both plans. We are pursuing grants to assist in the funding of injection for our community. We are concerned for present and future microclimate changes here in Green Valley. Shade and moisture loss from fewer oaks will affect all residents. Future fire-fighting issues are big concerns as we lose the protection from the oaks and the town becomes grassy hillsides.
Who Planted Our Oaks?
We owe a tremendous debt of gratitude to the California scrub-jay. Acorns ripen throughout fall. To get them through the winter to spring’s abundance, jays rely on stored food, overwhelmingly those durable acorns. One study estimated their yearly caches at some 5,000 to 7,000 acorns, each individually buried an inch or so beneath the soil’s surface. Perhaps half are recovered. To recover 3,000 acorns is an impressive feat, utterly beyond us. The jay is very intelligent and remembers where it buries its stash.
Of course, that still leaves 3,000 or more in the soil, largely safe from other predators and ideally placed for future growth. Acorns that simply fall upon the surface will almost never grow up to be trees. Most birds are too small to move them in one piece; squirrels and rodents concentrate their larders and do not travel far. Oaks need jays to plant them to achieve their full potential.
This is one of the most successful collaborations in the whole world of nature. There is a greater mass of oaks than any other tree on earth, and they grow nowhere without jays. Our adaptable squawkers now exceed the bounds of oaks by taking advantage of human foods, whether from feeders, picnics or orchards. But the oaks cannot do without their gardeners.
– Marin Independent Journal, Jack Gedney, August 30, 2020
What to Know Before You Mow
Every spring, many of those extra acorns sprout and become small seedlings. Before you mow or weedwack, take a walk around your property and look for oak seedlings. These are Green Valley’s future. Mark them with a protective wire or visible stake. All of the oaks in this valley began as small seedlings. How many thousands of seedlings have we trampled and mowed over the years?