By Tim Clancy, for Let’s Talk Plants! November 2023.
There Goes the Neighborhood
In the community of Cardiff-by-the-Sea, the South American Palm Weevil (SAPW) has made itself known. A part of Encinitas, Cardiff makes up its southmost end. Like the rest of the city, Cardiff is home to a diverse plant palette. San Elijo Lagoon is home to native plants which in turn attract native fauna. Most of the plant material in Cardiff would be considered “exotic” in that it is not native or near native.
Bismark palm, Bismarkia nobilis, in 2020 at the Cardiff Library.
The SAPW is also considered “exotic” and in this case it’s a plant killing machine. All over San Diego County you can see evidence of the weevil’s handiwork. I first saw the damage the weevil can inflict on Canary Island date palms over the border in Tijuana. Not long after that I was getting calls to diagnose “sick” date palms in the south county, then in La Jolla and now in Encinitas. This has all occurred in the span of about ten years.
Besides its favorite snack of the Canary Island date palm there are several other known hosts.
The garden at the Cardiff Library has a lovely collection of plants. Amongst that collection lived a stunning Bismark palm, Bismarkia nobilis.
Found natively among the flora of Madagascar, the Bismark palm can grow to 60 feet tall (200’ in its native range) and have a spread of up to 16 feet in Southern California. The leaves are silver greenish and are costapalmate (costapalmate describes a growth feature). I haven’t seen many mature specimens around San Diego and when I do see one, I am always amazed by the size of the fronds. Once mature they can, and quite often do, reach 4’ across. As you can imagine it’s not a palm for smaller gardens.
The weevils have just about wiped out the Canary Island date palms in Glen Park. The tree contractor was in the park in October 2023 removing several specimens (including the one the author got married under in 1990). In the end, as of this writing, eight of the trees have been removed because the weevil found them a suitable place to stopover for a snack and make baby weevils.
Just down the street from Glen Park is the San Diego County Library County Branch. One of the best features to me was the accessibility of the garden. You can look at the plants up close and really get a feel for how they grow, especially if you make a point to go several times a year. The Bismark palm had a trunk about 20’ tall and a +/-16’ spread. It was an absolutely magnificent plant standing sentinel in the Northeast corner of the garden.
The weevil (which does not fly well) made its way down the street and took up residence in the Bismark. The thing is, I didn’t see any signs or symptoms of a problem until one day the beautiful specimen I have admired for years collapsed. Close examination revealed a weevil nest in the “heart” of the palm.
Bismark palm, Bismarkia nobilis, at the Cardiff Library now.
Starting with Glen Park this has all occurred in the last 18 months in Cardiff. As of this writing I do not know of any pesticide that is labeled for treatment of the pest. Of course, there are some chemicals we suspect will prove to be efficacious and I know of some nurseries working on a preventative program. This is problematic in that all palms need to be treated (and regularly retreated) at great expense. I estimate approximately $1000.00 per year to apply a prophylactic insecticide per tree. This will prove to be burdensome to many people and as a result the Canary Island date palm will slowly disappear from Southern California.
