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UCCE solutions for invasive pest problem on popular landscape plant

The Issue

Myoporum plants, which are native to Australia and New Zealand, include several popular ground cover and tree species that are widely planted in California for erosion control and because of their aesthetic beauty, minimal management needs, and low water requirement. Until relatively recently, California plantings have not been bothered by any insect pests. Since 2005, however, an exotic thrips species new to the United States has caused great damage to Myoporum in landscape plantings and nursery stock throughout the coastal counties of California. Thrips damage to Myoporum is characterized by gall-like symptoms and distortion of new leaves. Terminal growth can be severely stunted and leaf curling or folding, with thrips populations present within the folds, is common and eventually leads to the death of the plant. Thrips populations in infested areas have grown to extremely high levels and large landscape plantings have been severely impacted. Until UCCE got involved, there was no scientific, research-based information available on the pest.

What Has ANR Done?

David Shaw and Jim Bethke of UCCE San Diego County have been working in cooperation with local commercial landscapers and the San Diego County Agricultural Commissioner’s office in an effort to identify solutions to the thrips problem. Although their research shows that at least one beneficial insect — the minute pirate bug — was present, it was not there in sufficient numbers to impact the thrips population. Shaw and Bethke conducted a series of management trials at various sites, including such well-known sites as the Del Mar Racetrack, to determine whether specific management methods could be used to control the pest and encourage plant recovery in the landscape.

The Payoff

Research-based studies improve knowledge base and management of Myoporum thrips

Through research-based studies by UCCE, the biology of the insect is better known. Several management methods, including some low-impact pesticides and application techniques, were identified as effective against Myoporum thrips and able to be used in the landscape with minimal impact on beneficial insects and the environment. Treated plants showed excellent recovery from severely gnarled terminal growth. Trials were conducted on heavy populations in the summer so they were curative in nature. This information has been made available via trade magazines, allowing landscapers and pest control advisors to benefit from the research. Armed with this research-based information, growers and landscapers can provide their customers with a high-quality specialty commodity that will protect Myoporum so it may continue its important roles in erosion control.

Clientele Testimonial

"Thank you for the research on the Myoporum. We are following the same program you laid out in your research with good results on controlling the thrips we were having such a big issue with. The research you did has directly resulted in a positive response from the Myoporum and saved the hedges in our chute." - Leif Dickinson, Turf & Landscape Superintendent, Del Mar Thoroughbred Club


Supporting Unit: San Diego North County Office

James A. Bethke and David A. Shaw
James A. Bethke, 951-775-7172, jabethke@ucanr.edu