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UCCE Helps Growers of Ornamental Eucalyptus Ravaged by an Invasive Pest

The Issue

Baby blue gum eucalyptus is grown for the production of fresh cut foliage for flower arrangements or it is dried, dyed and sold in preserved floriculture markets. It has been grown commercially in California from San Diego County to Sonoma County for 40 years. There is no other significant commercial production of baby blue gum elsewhere in the United States. Ornamental eucalyptus has been virtually pest-free, requiring only occasional pesticide treatments. However, in August 2003, tortoise beetles (Chrysophtharta m-fusca Boheman) were observed on ornamental eucalyptus in Orange County, Calif. Within a few years, this leaf-feeding beetle spread throughout Southern California in the major growing area of ornamental eucalyptus, and has caused very heavy feeding damage to terminal growth. In 2006, beetle populations in growing regions reached extremely high levels, resulting in nearly complete crop loss.

What Has ANR Done?

Because there was no information available on control efforts against this pest, Jim Bethke of UC Cooperative Extension in San Diego County worked in cooperation with local growers, the agricultural chemical industry, and the San Diego County Ag Commissioner's office in an effort to identify a solution to the immediate problem. Data from university research-based studies are needed to support registration of new products like chlothianidin, the latest in the new generation of pesticides, the neonicotinoids. The neonicotinoids are a good choice for control of tortoise beetle because they are reduced-risk, systemic products and will have a negligible impact on adults of the beneficial parasitoid species introduced to control another pest in the system, the blue gum psyllid. Trials on several neonicotinoids as well as older products were conducted at grower facilities to give the growers options that will match their particular operations.

The Payoff

Options Identified for Control of an Invasive Insect on Ornamental Eucalyptus

In UC studies, several pesticides were identified that are effective against tortoise beetles and can be used on this minor crop with a variety of application methods, including aircraft. Early-season treatment holds population levels in check so that little if any aesthetic damage occurs during the rest of the cropping cycle. This information has been made available to growers in all blue gum growing regions. Armed with this information, the growers can continue to provide their customers with a high-quality specialty commodity.

Clientele Testimonial

"This past year we had an infestation of tortoise beetle that could have completely destroyed our crop had it not been for the assistance and help of Jim Bethke and the San Diego UCCE. Without his and the UCCE support, I believe we would have gone out of business." Richard Russell, President, International Decoratives Co., Inc., Valley Center, Calif.


Supporting Unit: San Diego County

James A. Bethke, Staff Research Associate Floriculture and Nursery, UCCE San Diego, bethke@ucr.edu