Last week I received a question from Dave, a loyal reader. Since the issue might be important to many local gardeners, I’m going to devote this week’s Coastal Gardener exclusively to his question. Thanks Dave.
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These pictures, taken last July, show some of the first Olive Psyllid’s in the U.S., infesting trees in Newport Beach. |
In part, he explained that his olive trees were infested with a white sticky insect. He had brought samples to a local nursery where it was diagnosed as mealybug. Possible, but unlikely. I suspect that Dave’s olive tree pest was identified incorrectly.
The white, sticky, masses that Dave and other local gardeners might be seeing on their olive trees is more likely a very new pest in North America. It is called Olive Psyllid (pronounced SILL-id) or Euphyllura olivina. Olive Psyllid’s are pests exclusive to olives and are well established in the huge olive growing regions of the Mediterranean, but are new to local gardeners.
I recall very clearly my introduction to this pest. In July of last year I was talking to my friend John Kabashima of The University of California. I like talking to people smarter than me and John easily qualifies on this account. John holds a PhD in entomology and is always one of the most up-to-date pest experts in California. More than anyone, he always knows what’s going on in the county and has the most current new pest information.
So I asked, “What’s new, John”. His eyes brightened, his head rose and his voice raised. I new something was afoot. He told me about a new pest called an Olive Psyllid that had just been found a few days earlier on some olive trees at the Newport Beach library, near Fashion Island.
Being a bit of a bug nerd myself, the next morning I took a drive over to the library and, after searching several trees, discovered a few Olive Psyllid’s on some trees in their parking lot. A day or two later I checked another large stand of olive trees about a mile away. Sure enough, more Olive Psyllid’s. I reported them to John. In the ensuing months I’ve noticed Olive Psyllid’s at several more locations around town. This new pest is now well established in the Newport/Costa Mesa area as well as portions of coastal San Diego County. They are expanding their range and spreading to olives throughout the area, including Dave’s trees.
Adult Olive Psyllid’s are very small, inconspicuous, pale green insects, about 1/8” in length; hardly noticeable. Like many small garden pests, it is the immature stage that does most of the damage. While feeding, usually in small groups, the juvenile psyllid colonies secrete a white, waxy filament that covers the pests and allows them to feed on the trees leaves and tender new stems while protected from natural enemies. It is these white, frothy, cottony masses that the gardener may notice, not the insect.
Now a word of caution. Any time I or others write about a new pest we run the potential of creating a measure of panic among gardeners. Remember the Fire Ant panic. It is important to note that Orange County gardens are victim to many new pests and diseases every year. Bougainvillea Looper, Myoporum Thrips, Citrus Root Weevil, Brown Marmorated Stink Bug, Southern Mole Cricket, Citrus Leaf Miner, Tomato Yellow Leaf Curl Virus, Bamboo Mealybug, Magnolia White Scale and others are all new pests and diseases either already in your garden or at least heading in your direction. The Olive Psyllid is just another in a long wave of new garden pests.
So what should Dave and others do about his new Olive Psyllid friends? That’s what most gardeners want to know.
First, don’t panic. More likely than not, after an initial explosion in the population, the pest will reach a natural balance in our environment. Natural predators, parasites and parasitoids, either native or introduced will aid this process. Washing the foliage frequently with a strong stream of water will probably help as well. However, over reacting with the application of broad spectrum insecticides may do more harm in the long run, interfering with the natural pest-prey relationship. The chance of Olive Psyllid’s doing severe harm to a mature olive is unlikely. Nonetheless, if a young tree is threatened, a well timed application of a narrow-range, short-residual horticultural oil or insecticidal soap may help.
Thanks Dave for your question.
Ron Vanderhoff is the Nursery Manager at Roger’s Gardens, Corona del Mar
