From the UC Blogosphere...
California pest invasion rate increasing
Introduction of new invasive pests into California seems to be increasing, reported Todd Fitchette in Western Farm Press. The story was based on presentations at the recent professional crop advisors convention in Anaheim by UC Cooperative Extension specialists Mark Hoddle and UC Riverside entomology professor Richard Stouthamer.
Before 1989, Hoddle said, California saw about six new pest invasions per year. The number has risen to about 10 per year, and the cost amounts to about $3 billion annually.
Asian citrus psyllid, a relatively recent invader in California, has farmers particularly worried because of the pest's ability to spread the lethal bacterial disease huanglongbing in citrus. In late 2011, Hoddle's lab began releasing a natural enemy of the psyllid he collected in the Punjab, Pakistan, a stingless wasp called Tamarixia radiata.
According to the Western Farm Press article, Hoddle is now studying a second natural enemy of ACP - Diaphorencyrtus aligarhensis - in quarantine at UC Riverside.
Stouthamer is studying another troublesome invasive pest in California, the polyphagous shot hole borer. The pest attacks many tree species that shade California streets, landscapes and parks; their greatest threat to agricultural production appears to be in avocados.
At the meeting, Hoddle said there is a growing and vocal minority of ecologists who believe invasive species are not such a serious problem, Fitchette wrote.
“They think we should just relax and let them install themselves in the environment and do whatever they like,” Hoddle said. “I think that's a wrong viewpoint to be taking with a lot of these organisms.”
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Nightmare in midtown: Brown marmorated stink bugs
A population of invasive brown marmorated stink bugs have settled in Sacramento's mid-town, a development that Sacramento Bee writer Debbie Arrington says is "worthy of a Halloween creature feature."
"Wow, I'm being overwhelmed with calls about brown marmorated stink bugs getting into people's home, as well as restaurants and businesses," said Chuck Ingels, UC Cooperative Extension advisor in Sacramento County. "It's that time of year again!"
When days get shorter and cooler, the BMSB start looking for a place to spend the winter. Frequently, that's inside homes and buildings.
Ingels told the reporter he is keeping track of the BMSB invasion. Residents are asked to fill in an online survey to report BMSB finds. For identification help, residents may deliver BMSB in a sealed plastic bag or container to the UCCE office, 4145 Branch Center Road, Sacramento, or they can email clear photos to cesacramento@ucanr.edu.
Ingels said fairly large populations of BMSB have been found in Citrus Heights near Auburn Boulevard and River Park north and west of CSU Sacramento.
"Most of the others are single finds," he said.
For more information on BMSB identification and management, read a Pest Note posted by the UC Integrated Pest Management program.
Redbud Leaf Spots
Help for the Home Gardener from the CCMG Help Desk
Client Question:
The client brought a leaf sample into the Help Desk. The leaf was from a Redbud tree. It was covered with spots. The client wondered if we could help with diagnosis and treatment of the problem.
CCMG Help Desk Response:
The spots on the leaf are most likely caused by a fungus, Cercospora. The web page at http://bit.ly/ZePPMa was generated from a Google search of “cercospora leaf spot redbud” It has photos which you could check to see if they look like your problem.
It looks like your tree is an Eastern Redbud (Cercis canadensis). My research indicates that Cercospora is a known problem of this specie. However our University of California information does not list this. Here is the UC page with some additional Redbud information, although you will notice that the leaf they show is the Western variety which is a little different. http://www.ipm.ucdavis.edu/PMG/GARDEN/PLANTS/redbud.html. Even though UC doesn't list such leaf spots on the Western Redbud (Cercis occidentalis), most Western Redbuds in my neighborhood exhibit similar leaf spot problems.
The good news is that most fungal diseases, including Cercospora, will not seriously damage the tree, but it will not look its best at times, including the loss of some leaves. The best way to manage this is to give the tree good cultural care, as stressed trees are more susceptible to problems. Eastern Redbuds, being originally from the Eastern U.S., need regular water and good drainage, so you should water when the top 2 inches of soil are dry, but not so much that the soil stays wet. A several inch layer of mulch out to several feet past the drip line of the tree will help, but make sure the soil close to the trunk is clear of mulch. Also using drip or soaker type irrigation near the drip line will help; to keep the leaves dry, you should not use overhead watering. If the foliage is thick you can lightly prune out the tree to improve air flow, and you can prune off and discard any dead wood and badly affected leaves to remove some of the fungal material. Clean up fallen leaves and debris under the tree as the fungus can survive in fallen leaves and twigs. You should avoid over fertilizing, as new growth is more susceptible to diseases. Anti-fungal sprays are not usually recommended in the home garden and are not usually helpful.
Like most landscape trees, they sometimes have their minor problems, but with some minimal care, the Eastern Redbud is a beautiful and useful garden tree that can add significantly to your home landscape.
Contra Costa Master Gardeners Help Desk
Editor's Note: The Contra Costa Master Gardener Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523.
We can also be reached via telephone: (925) 646-6586, email: ccmg@ucanr.edu, and we are on the web at http://ccmg.ucanr.edu/
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