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Palmaggedon: Are California’s Palms about to Face the Perfect Storm?


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Palmaggedon: Are California’s Palms about to Face the Perfect Storm?

By Mark Hoddle | July 24, 2011


Two species of giant palm weevils, Rhynchophorus ferrugineus (commonly known as the red palm weevil) and Rhynchophorus palmarum (South American palm weevil) have both been detected in Southern California. The red palm weevil (RPW) was officially discovered in Laguna Beach in Orange County (California USA) in September 2010. The beetle has been declared by FAO as a category-1 pest of date palms in the Middle-East. RPW, native to south east Asia, has been particularly devastating following its successful invasion into Mediterranean countries in Europe and Africa (e.g., Egypt). For about one year now, the California Department of Food and Agriculture (CDFA) has been intensively monitoring for RPW in Laguna Beach with approximately 250 RPW traps baited with aggregation pheromone and fruit. These traps have failed to capture adult RPW. Visual ground inspections of palms in Laguna Beach have identified trees potentially infested with RPW. One palm was inspected on 25 May 2011 and physical inspection confirmed feeding damage from RPW, but NO live RPW were found. This palm was treated with insecticides. On 2 June 2011, a second palm displaying symptoms of RPW damage was inspected physically. Again, feeding damage was confirmed but NO live RPW were detected. This palm was also treated with insecticides.

Damaged Palm in background compared to healthy palm in foreground. A collapsed palm crown is indicative of weevil feeding damage.

In December 2010 reports were received from palm enthusiasts in Tijuana Mexico of dying Canary Islands palms and these moribund palms were displaying symptoms similar to that expected from a RPW infestation. Physical inspection confirmed the presence of live palm weevils in at least one palm, and this weevil was officially identified at Rhynchophorus palmarum, the South American palm weevil (SAPW). This weevil is native to Mexico, Central and South America and is a well known palm pest, especially of coconuts. This weevil has been recorded feeding on 35 plant species in 12 different families, but is found predominantly on palms. SAPW has been problematic in Puerto Vallarta where in 2008 it was apparently linked to the mortality of more than 500 coconut palms in this popular tourist area.

In addition to the damage that SAPW larvae inflict while feeding inside the palm crown and trunk, this weevil also vectors a nematode, Rhadinaphelenchus cocophilus, which causes red-ring disease of coconut. The contamination of healthy plants with red-ring disease occurs only if SAPW are present. The nematode cannot survive outside of it’s palm hosts and it is moved from palm to palm by adult weevils. The nematode may also cause disease in oil palms, Elaeis guineensis.

Adult Rhynchophorus palmarum found next to its palm host

Following the discovery of SAPW in Tijuana, the CDFA commenced a monitoring program in San Ysidro in San Diego County (California USA) in March 2011. The area under surveillance with traps baited with SAPW aggregation pheromone is close to the USA-Mexico border. Mexican collaborators have also deployed SAPW pheromone traps in Tijuana to monitor for this pest. Monitoring efforts have trapped adult male and female SAPW weevils in San Ysidro and Tijuana that flew into traps in response to aggregation pheromone. So far no infested palm trees have been found in the San Ysidro area. Consequently, it is difficult to determine whether or not SAPW has breeding populations in San Diego County as pheromone traps may simply be catching SAPW dispersing from Tijuana into Southern California. This situation is being monitored very closely by the CDFA and the USDA.

Potentially, for the first time, an extraordinary invasion scenario may be unfolding in Southern California with respect to exotic palms and invasive palm weevils. Should RPW and SAPW establish in Southern California this will be the first time these two weevils have ever been together in the same place at the same time and potentially attacking the same palms simultaneously!

So what could this mean for the palms of Southern California? This is obviously difficult to answer, but one potential concern could be the ability of RPW to acquire from SAPW the red-ring disease nematode and spread it as well. If this happens, it may increase the vector capacity for this nematode as two weevil species instead of one could spread the nematode to susceptible palms. This could cause a severe disease epidemic for California’s palms. Should both palm weevils infest the same palm tree will this speed up the rate of palm mortality or will different larvae species attack each other while competing for food and slow the rate of palm mortality? Could both weevil species interbreed and produce less fit offspring (hybrid or outbreeding depression) or could hybridization create a more aggressive strain of palm weevil (hybrid vigor)? Finally, what is amazing about speculating over this situation is that it is an entirely a human-made problem! People have moved exotic palms to Southern California (e.g., Canary Islands palms from the Canary Islands and date palms from the Middle East), and people have facilitated the movement of exotic palms weevils from South East Asia (i.e., RPW) and Latin America (i.e., SAPW). People have also provided an ideal but highly artificial environment (i.e., irrigated urban and agricultural landscapes) for invasive weevils to potentially establish and proliferate on exotic palms in a part of the world where none of the players (i.e., palms and weevils) are native, but the climate is agreeable for their mutual co-existence.

Topics: Invasive Species, Mark Hoddle, News, Red Palm Weevil, Rhynchophorus palmarum | 9 Comments »

9 Responses to “Palmaggedon: Are California’s Palms about to Face the Perfect Storm?”

  1. Darren@Essex Pest and Bird Control Says:
    July 29th, 2011 at 7:00 am

    Great stuff. I came across your blog after reading about bed bugs and following a link, really good detailed writing you have given, very educational, I really like it, thanks. I also have a video of a bad bed bug infestation I treated if you would like to use it on your other site.

  2. Anne Thomas Says:
    August 1st, 2011 at 11:04 pm

    I hope this could treated and prevented.

  3. Amand Gates Says:
    September 18th, 2011 at 9:39 am

    What is the cure for it? Are there any pesticides which can prevent this?

  4. Mark Hoddle Says:
    September 18th, 2011 at 10:09 am

    Yes pesticide treatments are possible and can be effective. However, they are costly and difficult to apply as the products that will be most effective must move within the palm to kill the weevil larvae (these are systemic insecticides and can applied to the trunk or as drench to the soil) and a different type of pesticide, a contact insecticide may need to be applied to the foliage and crown to kill adult weevils that are flying into the palm tree to feed, mate, and lay eggs. These pesticide applications hae been discussed in some detail in two previous blogs on treating infested palms in Laguna Beach.

  5. portable satellite dishes Says:
    October 18th, 2011 at 6:44 am

    i have a feeling there are some treatments available but check out some videos on youtube to be sure. i was watching some videos earlier on youtube about getting treatment for bed bugs. thats how i found your blog

    good luck and nice blog, thanks, jen

  6. California Blogger Says:
    November 7th, 2011 at 5:52 pm

    These insects are indeed making their way from Mexico northward. Now I hear they have been spotted in Ventura County (THESE WEEVILS HAVE NOT BEEN FOUND IN VENTURA – CISR MODERATOR). Palm trees symbolize California to the rest of the world and they’re beautiful. We cannot lose them!

  7. Seattle Facelift Says:
    January 5th, 2012 at 1:07 pm

    Oh my gosh. Those things look so mean! I hope they don’t wreck the palm trees

  8. Bird Control London Says:
    January 24th, 2013 at 5:54 am

    OMG, I hope they all are gone now !!

  9. Mark Hoddle Says:
    January 24th, 2013 at 8:12 am

    Unfortunately the number of trap captures for this giant weevil are remaining pretty consistent along the California-Mexico border. Incredibly, in southern Texas last year, they caught this beetle in monitoring traps that use the aggregation pheromone. So it would appear that this weevil has the ability to fly a long way, and given the regular capture events it is likely now to be just a matter of time until populations establish in San Deigo County and move outwards from there.

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