Has the Red Palm Weevil Gone Extinct in Laguna Beach?

By Mark Hoddle |


The Situation: On 27 March 2013, a Canary Island palm on the Pacific Coast Highway that had been previously inspected and treated for red palm weevil (RPW) infestation in June 2011 was removed by MPA Landscape Services (Chuck Galanti). The palm was removed because it was causing structural problems to an adjacent building, and notbecause it was damaged by RPW.

The felling of this palm provided an excellent opportunity to examine the crown for evidence of RPW activity two years after the palm was treated with insecticides.

Careful inspection of every frond that was removed failed to find evidence of RPW tunneling, holes, or RPW cocoons wedged into cavities at the bases. This damage had been observed in June 2011.

Further, dissection of the meristematic bulb of the palm, the most preferred feeding site for RPW larvae, failed to detect any evidence of RPW feeding activity. No tunnels or feeding damage was observed, no larvae, pupal cocoons, or adults (in 2011 body parts of dead RPW adults were found in the crown of this tree) were found.

Has RPW Gone Extinct in Laguna Beach? The last live RPW to be captured in Laguna Beach was January 2012 when a single adult was trapped in a CDFA bucket trap baited with aggregation pheromone, ethyl acetate synergist, and fruit. Enhanced trapping trials run over June-July and October-November 2012 using stacks of cut date palm logs and pheromone baited bucket traps failed to capture RPW.

Given the lack of RPW captures and no recent signs of RPW feeding damage to Canary Island palms in Laguna Beach it is possible that RPW has either gone extinct or populations are so low as not to be noticeable.

International monitoring protocols suggest that before a pest can be considered eradicated monitoring programs must fail to detect the pest for three consecutive years.

Why Would RPW Go Extinct in Laguna Beach? There are several potential reasons why RPW populations may have gone extinct in Laguna Beach. The first impediment to successful invasion could be a lack of genetic diversity. DNA analyses of RPW collected from Laguna show very little genetic variation suggesting that the founder population was small. Consequently, inbreeding may have resulted in an unhealthy and weak population that was susceptible to environmental events that cause extinction (e.g., climate or pesticides). Second, the climate in Laguna Beach is cool, much cooler year round than the tropical climates of southeast Asia where this weevil is native. Low temperatures may not be favorable for year round RPW breeding, development, and dispersal. This would affect population growth and stability. Third, the variety of RPW in Laguna (black with a red stripe) may not perform well on Canary Island palms. Its preferred host in southeast Asia is coconut palm. There are no coconuts in Laguna Beach as it is too cool for this palm to grow well. Fourth, targeted pesticide treatments of RPW-infested palms may have been very successful at exterminating small RPW populations before they could grow large enough to spread into more favorable areas.

Are California’s Palms Safe from Palm Killing Weevils? No! There is another palm killing weevil invading southern California from Mexico. This is the South American palm weevil, Rhynchophorus palmarum. This pest has killed Canary Island palms in Tijuana and adult weevils have been trapped in San Diego County and southern Texas. It may only be a matter of time before this pest establishes in southern California and starts killing palms.

The Back Story: Red palm weevil (RPW) was first discovered in Laguna Beach in October 2010 following the inspection of a Canary Island palm that had died on a residential property. The infested palm was removed and destroyed.

RPW is native to southeast Asia and has been moved internationally through trade in live palms. This beetle is a highly destructive palm pest that has invaded many countries and killed hundreds of thousands of palm trees.

It is possible that RPW was intentionally introduced into California for food as the larvae are edible either cooked or raw.

The Response to Detecting RPW: In response to this RPW find in Laguna Beach, a red palm weevil Technical Working Group (TWG) was formed to develop a management plan for this highly destructive invasive pest.

A pheromone trapping program was initiated to delineate the infestation zone in Laguna Beach and a series of town hall style meetings were conducted in Laguna Beach and Coachella Valley by the California Department of Food and Agriculture (CDFA) to alert the public and stakeholders (e.g., date and ornamental palm producers) to this problem.

Additionally, a surveillance program was initiated and this was a joint effort between the University of California Cooperative Extension (John Kabashima [Orange County] and Mark Hoddle [UC Riverside]), the Orange County Agricultural Commissioner’s Office (Nick Nisson), and the CDFA (Mohammed Alzubaidy).

The surveillance program had two objectives: (1) to find RPW infested palms in Laguna Beach and treat them with pesticides,and (2) to run enhanced trapping trials using CDFA’s RPW pheromone traps and stacks of cut date palm logs to lure flying RPW adults to traps.

Date palm logs were acquired for these trials via cooperative efforts with Cocopah Nurseries (Duane Young) and Hadley Dates (Albert Keck) in the Coachella Valley.

This enhanced trapping trial design was motivated by RPW research that was completed in the Philippines.

Two enhanced trapping trials replicated across three different sites were conducted for four-five weeks in Laguna Beach over June-July 2012 and again in October-December 2012. These super-trapping-trials failed to capture any RPW adults (adult weevils are attracted to pheromone traps and fermenting palm logs to mate and feed and are often captured in bucket traps as a result.)

There is now mounting evidence that RPW may be extinct in Laguna Beach or populations are too low to be detected with currently available tools.

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