- Author: Iqbal Pittalwala
We've been getting reports of coast live oak decline along the coast, well, here's one of the causes:
RIVERSIDE, Calif. — A fungus associated with the western oak bark beetle is causing a decline in coast live oak trees in Southern California by spreading “foamy bark canker disease.”
“We have found declining coast live oak trees throughout urban landscapes in Los Angeles, Orange, Riverside, Santa Barbara, Ventura and Monterey counties,” said Akif Eskalen, an assistant specialist in cooperative extension in the Department of Plant Pathology and Microbiology at the University of California, Riverside.
Eskalen recovered the fungal species, Geosmithia pallida, from tissues of infected coast live oak trees and performed pathogenicity tests on it in his laboratory at UC Riverside. The tests showed that the fungus is pathogenic to coast live oak seedlings and produces symptoms of foamy canker.
The western oak bark beetle, which spreads the fungus, is a small beetle — about 2 millimeters long — that burrows through the bark of the coast live oak tree, excavating shallow tunnels under the bark across the grain of wood. Brown in color, this beetle is native to California. Female beetles lay their eggs in the tunnels. It is not known at this time if the beetle infects trees other than coast live oak trees.
Symptoms of foamy bark canker disease include wet discoloration on the trunk and main branches of the infected coast live oak tree. This discoloration surrounds the entry holes that the western oak bark beetle makes to burrow into the tree. Multiple holes can often be seen on an infected tree.
“When you peel back the outer bark of the infected area, you see bark (phloem) necrosis surrounding the entry hole,” Eskalen said. “As the disease advances, a reddish sap may be seen oozing from the entry hole, followed by a prolific foamy liquid. This foamy liquid, the cause of which remains unknown, may run as far as two feet down the trunk.”
Eskalen explained that when the infection is at an advanced stage, the coast live oak tree dies. Currently, no control methods are in place to control the fungus or the beetle.
If you suspect your coast live oak tree has the symptoms described above, please contact your local farm advisor, pest control advisor, county agricultural commissioner's office or Eskalen at akif.eskalen@ucr.edu.
- Author: Kathy Keatley Garvey
"Where do foraging bees go to die?"
That question was asked this week of honey bee guru Eric Mussen of the UC Davis Department of Entomology, who serves as the statewide Extension apiculturist.
"Do they return to the hive? Do they retire and live out their last days inside?" he was asked.
We've all seen worker bees in the throes of death. After all, they live only four to six weeks in the busy season. But the queen bee, which can lay some 2000 eggs a day, quickly replaces them.
"Since we do not know exactly where they go, we say that they fly off in the final moments of life, lose altitude and land on whatever is beneath them, moribund," Mussen says. "They are still able to sting for quite a few minutes, as can be attested to by neighbors who find moribund bees in their lawns or swimming pools, but they die relatively soon. Bees have enzyme systems that deal with flight and when the enzymes give out, so does flight."
Mussen points out that "a few of the dying bees, maybe 15 or so, of the 1,000 or more that die daily (in a colony) during the spring, summer, and fall, do die in--or in front of--the hive."
When those bodies lose some moisture, the "undertaker bees" carry away the lighter-weight bodies and drop them 150 feet or more away from the hive, studies show. "Most of the rest just drop, somewhere, when they no longer can forage or stay in the air," Mussen says. "Bees do fly up to four miles from the hive in any compass direction, so they drop out there in that 50-square mile area."