I have a Laurus nobilis tree that was planted in my yard by a landscaper. I noticed the tree was looking very sticky. Many of the leaves were curling.
I thought I might be dealing with aphids, so I sprayed the tree real good with water.
Then lots of little black bugs with red snouts began falling from the tree and a large number of yellow jackets were flying from the tree.
Can you tell me what the bugs are and how to get rid of them before they kill my tree?
Jean Sutton, El Dorado Hills
The red-snouted insects in your letter might be adult soldier beetles. If so, they were feeding on the aphids in your laurel tree, according to UC master gardeners Liz Haines and Mary Griggs. Without a photo, positive identification isn't possible.
Soldier beetles are harmless and are included in a group of insects that are considered "the good bugs."
The sticky material on the leaves of your tree may be honeydew excreted by the aphids. Honeydew, like its name, is sweet and attracts yellow jackets and bees. The soldier beetles are interested in the aphids.
Spraying the tree with water is an excellent response to eliminating aphids. (It knocks them down and their soft bodies can't survive the fall.) Had you not sprayed the tree, the beetles would have eventually eliminated the aphids on their own, but would not be as efficient.
Another possibility is that your tree has an infestation of scale. Laurus nobilis trees are susceptible to black scale insects, which also produce honeydew.
Scales are often well-controlled by beneficial predators and parasites. If scales are too numerous, a well-timed and thorough spray using horticultural oil applied either during the dormant season (which is now) or soon after scale crawlers become active in late winter to early summer should provide good control.
If this fails to work, a soil application of the systemic insecticide imidacloprid can provide season-long control of soft scales such as black scale. This product is available to homeowners under the brand name Bayer Advanced Garden Tree and Shrub Insect Control.
For more information on controlling aphids and scale, please send a self-addressed, stamped business-size envelope to: PN 7404 (for aphids) or PN 7408 (for scale), UC Cooperative Extension, 4154 Branch Center Road, Sacramento, CA 95827.
These pest notes are also available online at www.ipm.ucdavis.edu.
Questions are answered by master gardeners at the UC Cooperative Extension services in Sacramento and Placer counties.
Send questions to Garden Detective, P.O. Box 15779, Sacramento, CA 95852. Send email to firstname.lastname@example.org. Please put "Garden Detective" in the subject field and include your postal address.
To contact your UC Extension directly, call:
Sacramento: (916) 875-6913; 9 a.m.-noon and 1-4 p.m. weekdays
Amador: (209) 223-6838; 10 a.m.-noon Monday through Thursday; email ceamador.ucdavis.edu
Butte: (530) 538-7201; 8 a.m.-noon and 1-5 p.m. weekdays
El Dorado: (530) 621-5512; 9 a.m.-noon weekdays
Placer: (530) 889-7388; 9 a.m.-noon on Tuesdays, Wednesday and Thursdays or leave a message and calls will be returned
Nevada: (530) 273-0919; 9 a.m.-noon Tuesdays through Thursday or leave a message
Shasta, Tehama, Trinity: (530) 225-4605
Solano: (707) 784-1322; leave a message and calls will be returned
Sutter, Yuba: (530) 822-7515; 9 a.m.-noon Mondays and Tuesdays and 1-4 p.m. Thursdays
Yolo: (530) 666-8737; 9-11 a.m. Tuesdays and Fridays, or leave a message and calls will be returned