By Karen Brainard
Thomas Stephan is on a quest to save oak trees.
"I can't watch the oak trees die anymore," the Ramona resident said. "I had to do something."
As a certified arborist who operated Stephan's Tree Maintenance for 32 years, he knows a lot about trees. In 2005 he switched from running a tree service business to installing barn owl nest boxes for organic rodent control. Now, with the goldspotted oak borer infesting oak trees and the drought, he is putting a focus on tree health from the ground up.
Stephan said he was the first arborist called to troubleshoot a mass die-off of live oak trees eight years ago near Boulevard. Upon inspection, he found small "D" shaped larval borer exit holes on the bark and branches. That led to the discovery of the goldspotted oak borer infesting oak trees. The beetle is believed to have come from Mexico in a firewood shipment, he said.
For nearly a decade, Stephan has watched the pest take over San Diego County.
"It had gained tempo all the while," he said. "The government experts say there are no known predators to this bug."
As if the pest wasn't enough, the drought is putting additional stress on trees.
"A stressed tree is vulnerable to fungi and insects," noted Stephan.
Die-offs of oak trees can be seen locally on the eastern flank of Mt. Woodson just above the forestry headquarters and with scattered infested trees on state Route 67 from Mt. Woodson to Country Wine & Spirits market.
San Diego Country Estates is beginning to see the full effect of this pest, he added.
Three types of oaks are affected: canyon oaks, live oaks and black oaks.
Stephan wants to treat the trees before they fall victim to the oak borer. He performs site inspections and can make a diagnosis. Keeping the tree hydrated is important.
He will drill holes in the dirt along the drip line — the area under the outer edge of the branches. Then he mixes worm food and worm castings and pours that into the holes.
"This is how I keep the trees healthy," he said of the worm mixture.
He tops off the mixture with fish emulsion.
Stephan explained that the worms will hatch, eat the food and tunnel about the drip line, fluffing up the soil
"This allows the roots to penetrate the soil, growing out, searching for water and nutrients. This successfully accomplished, allows the rest of the tree to grow, improving the general health of the tree," he said.
After adding the mixtures, Stephan rakes mulch over the area under the tree, which he said is very important to keep in the moisture.
Mulch is an insulating blanket between the weather, sun and rain, and the mineral layer, he explained.
"Very little moisture can penetrate this hardened soil, and soon a hard crust layer is formed," he said. "Year after year, if the situation is not reversed, the trees will stress and die."
After his procedure, Stephan advises his customer about irrigating the tree. For someone who does not have drip irrigation, he can insert tubes in the holes into which he pours water.
Trees are not the only plants he can doctor.
According to the arborist, he has a mixture with beneficial fungi that works well on plants that can get a powdery mildew like roses and wine grapes.
For more information about Stephan's service or his barn owl nest boxes, contact him at 760-445-2023.