In 2005 an exotic species of thrips new to the U.S was discovered in Orange County, California. Now identified as Klambothrips myopori Mound and Morris, it has caused considerable damage to Myoporum laetum and M. 'Pacificum' (Also known as Myoporum 'South Coast') in landscape
plantings and nursery stock in Los Angeles, Orange, San Diego, Santa Barbara, and Ventura counties. By the summer of 2008 it has also been reported in numerous locations around the San Francisco Bay area.
We first learned about this pest from an article by Ventura Farm Advisor Dr. Jim Downer titled "New Thrips Pest Attacks Myoporum"
in the July 26, 2006 Ventura County UC Cooperative Extension Newsletter "Landscape Notes" (Vol. 19, No. 3).
More details on this pest were given at the at the California Ornamental Research Foundation (CORF) meeting held on September 27, 2006 in Ventura
where James Bethke, UC Cooperative
Extension Farm Advisor for San Diego County, mentioned the pest and showed pictures of the damage it had caused during his talk titled "Nursery IPM practices".
On June 10, 2008 CORF sponsored a grower tour, visiting nurseries and cut flower growers in Ventura and Santa Barbara counties, with the theme "Remaining Competitive in Today's Market". The group visited San Marcos Growers for a tour of the facilities and discussion of the nurseries diverse product
mix. San Marcos Growers also hosted two short sessions for continuing education credits. One session, conducted by San Marcos Growers General Manager Randy Baldwin, addressed the advantages of using plants suitable to our dry California climate, including native California plants and plants from other
mediterranean climates or plants, such as many succulents, that come from climates that are even drier. The second session discussed the current state of the Myoporum thrips infestation in California. This session had two parts with Randy Baldwin showing examples of infected plants from
nearby plantings and sharing observations he made about resistant varieties of Myoporum. Since first observing the thrips in nearby landscapes and then on plants in the nursery, Randy noticed that Myoporum laetum 'Compacta'
had remained unaffected by this pest and would possibly be a suitable replacement for a Myoporum laetum hedge. Myoporum laetum 'Compacta' does not grow as tall as Myoporum laetum 'Carsonii' (the common Myoporum laetum cultivar) but can make a dense hedge to 15 feet tall. Randy also noted that
Myoporum parvifolium 'Putah Creek', a cultivar from UC Davis, has not been damaged by these thrips and would make a suitable replacement for Myoporum 'Pacificum'.
[As an addendum to this page - Doug Zylstra of West Covina Wholesale Nursery discovered a Myoporum laetum that has remained free from thrips through several years of trials. This plant has been introduced into the nursery
trade as Myoporum laetum Green N Clean ]
The second part of the Myoporum thrips session featured James Bethke discussing the pest, predatory insects, and trials using several chemical treatments that he and David Shaw, Landscape Farm Advisor for San Diego County, had conducted.
Jim noted that, as yet, there was little known about Klambothrips myopori and that it had only recently been described in the scientific literature from samples collected in California and sent to Australia. He described the damage the thrips causes as characterized by gall-like symptoms and distortion of new leaves with terminal
growth severely stunted and leaf curling or folding and compared it to similar damage caused by Cuban laurel thrips, (Gynaikothrips ficorum) on Ficus species. He also described the trial he did with David Shaw to determine the efficacy of three insecticides, Avid (abamectin), Merit 21 (imidacloprid) and Conserve (spinosad),
on controlling this pest. The trial was conducted in late summer and fall in 2006 on an existing landscape of Myoporum 'Pacificum' at Arrowood Golf Course in Oceanside, CA. where the thrips infestation was moderate to heavy. They also made observations to identify any biological agents that may be affecting thrips populations.
In this trial they found that Spinosad (Conserve) and Imidacloprid (Merit) significantly reduced the mean number of thrips compared to the control and that Abamectin (Avid) did not, though damage observed declined over time for all treatments during the trial. They also found that minute pirate bugs, Orius tristicolor, natural
predators of thrips, were observed in almost every sample, indicating that predation was occurring but also found that populations of this predator declined over time on treated foliage and were eradicated on the Imidacloprid (Merit) treated plants. While reporting that a great number of Minute pirate bugs were observed feeding
on K. myopori in the trials, these predatory insects did not cause a significant reduction of thrips numbers or reduce damage to the plants. The study concluded that control of Klambothrips myopori and reduction in damaged Myoporum will most likely involve the use of insecticides but that other beneficials, resistant cultivars,
and other IPM methods may be available in the future.
For more detailed information on this trial see "Myoporum Thrips Control", the research paper by James A. Bethke and David A. Shaw that was handed out at this CORF meeting.