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Palm Weevil 101

Aired 8/22/11 on KPBS Midday Edition.

All you need to know about the latest pest threatening the multimillion dollar agriculture industry in San Diego County.

Various life stages of the South American Palm Weevil.
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Above: Various life stages of the South American Palm Weevil.


Report Palm Weevils

Report Palm Weevils

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It is the perfect picture of an ugly bug. The South American palm weevil is several inches long with a black shell, spindly legs and a face only another weevil could love. Last week, San Diego County officials announced that eight of these bugs were found in San Ysidro. It turns out these bugs are a lot more than ugly. They pose a threat to a wide variety of palm trees, though how much of a threat is still not known.


Eric Larsen, is executive director of the San Diego Farm Bureau

Lisa Leondis, is San Diego's Agriculture Commissioner, she oversees County Department of Agriculture, Weights and Measures.

Read Transcript


CAVANAUGH: This is KPBS Midday Edition. I'm Maureen Cavanaugh. It is the perfect picture of an ugly bug. Of the South American palm we shall is several inches long with a black shell, spindly legs and a face only another we shall could love. Recently, San Diego County officials announced that 8 of the bugs were found in Ysidro. They pose a threat to a wide variety of trees. How much of a threat is still not known. Joining me to talk about the we shall discovery are my guests. Eric Larsen is executive director of the San Diego farm bureau.


CAVANAUGH: And Lisa Leondis is San Diego agricultural commissioner.

LEONDIS: Hi, Maureen.

CAVANAUGH: Have we ever seen this kind of palm weevil in San Diego before?

LARSEN: No, we haven't. We have had weevils before, but nothing like this. And it's kind of interesting 'cause we have this artificial population of palm trees in San Diego County that we've all learned to love. Now we have a pest that wants to come in and lunch on them.

CAVANAUGH: I didn't like the way you said nothing like this. What do these palm weevils do to palm trees?

LARSEN: What they do, our palm trees all in all have been pretty immune from threats over the years. But what this weevil does, it comes in and the larva of the weevil feasts on the crown, the very growing top of the palm tree, and they continue to feed, and the adults lay eggs, and the life cycle continues until the palm tree is dead. And then they crawl away from that tree onto the income one.

CAVANAUGH: Do we know how these palm weevils get here?

LEONDIS: We're supposing that these weevils are actually flying over the border. This is a known infestation in Mexico at this time. Officials have confirmed that, and trapped about the same number that we have on our side. However, Mexico is not treating these as a concern. They're more worried about a different kind but very similar weevil. So right now, we're supposing that they're flying across the borer. They're strong fliers. We have not seen any infestations on this side of the border the. So right now, we're not completely sure.

CAVANAUGH: All you found is that eight in San Ysidro right?

LEONDIS: We're up to 9, and 1 has been found in Calexico.

CAVANAUGH: Can you tell by looking at a palm tree that a palm weevil has gotten into it?

LEONDIS: Absolutely not. It's very difficult to detect these weevils once they're inside the tree. Once a female has bored a hole into the crown and laid her eggs in there, the whole family goes on about their life cycle and has no reason to come out. As high up as some of these palms are, it would be very difficult to detect that. When the infestations become more serious, you might see pupil cases which are fibers of these insects that are wound up kind of in a ball or an elongated ball the size of a very fat cigar. At the base of the tree, sometimes the leaf sheaths come off the leaves, and instead of being sheets of paper or cardboard, they actually look like Swiss cheese. Those are some of the best ways to determine that something is going on in the tree.

CAVANAUGH: Eric, a public forum was held about the discovery of these palm weevils. What did you tell the public about this?

LARSEN: Well, what the officials, there were folks from the yesterday of California, United States department of agriculture, California department of food and agriculture. And they were telling the attendees what to watch for, what to look at, and how to see this pest. And as Lisa said, you really can't tell it's there. So really the things they were showing people was what a tree looks like once it's pretty well decimated. So if we do see it, there's an opportunity to get at it. But there was really an appeal at that meeting for everybody to become the eyes and ears and be looking for this pest in the landscape.

CAVANAUGH: Do we know how long it might take for a palm weevil infestation to really undermine a tree so that it's gone?

LARSEN: That might be a question for Lisa. It's a little bit of a technical one or someone who might know more about the biology of the weevil to answer that.

LEONDIS: Well, what's interesting is the female can lay anywhere from 250 to 700 eggs at a time. And it takes only about four months for a whole life cycle to occur within the tree. And it only takes -- and we're kind of using different species as an example, but maybe 30 to 50 weevils to kill a tree. -- And at four months that life cycle could go fast. But we've also not seen the damage that we expected in some areas like up in Laguna Beach where a different specific was found, we didn't see palm trees dropping up left and right. That's why we're not entirely sure how this species will act here in our climate and in our area.

CAVANAUGH: I see. Eric, give us some idea about how big a business is growing palm trees in San Diego.

LARSEN: Well, San Diego County is the number one horticultural county in the United States. So it's a billion dollar business a year here. When you look at all horticulture. And palms are a significant portion of that. So we're really the area in the United States supplying the palm trees to all of Southern California and to Arizona, the southern states and into the east. So we don't know exactly how many dollars worth of palm trees are grown here, but it's in the tens of millions of dollars, and lots of jobs and adding the trees to the landscape.

CAVANAUGH: Do we have an idea that if some varieties of palm trees are more at risk than others from this weevil?

LARSEN: Yeah. The Phoenix Canaries, which is the canary island date palm, that's the real stately palm tree that we have in, like, Balboa Park and down by the airport. It's a very heavy trunk with a big crown, the pineapple looking top of it. That seems to be the favorite of this pest so far because it's a big crown that they can land in and have a lot of space to work in.

CAVANAUGH: Lisa, what's being done to prevent infestation? Anything?

LEONDIS: Well, right now, we're trying to determine how far this weevil has been distributed within the county. The first part is to figure out if there's some parts that don't have the weevil at all. Right now the department of food and agriculture are looking at whether or not a quarantine is needed to control the pest.

CAVANAUGH: That's what I was going to ask next. So this is something that is perhaps being considered?

LEONDIS: Well, it is being considered. And it would have a devastating impact on our local nurseries here in the county. So it's not something that anybody wants. At this point, if we can, though, determine that there are no weevils, for instance, in North County, if a quarantine is enacted, we could leave out that portion of the county and save many of our palm growers.

CAVANAUGH: What can be done if anything, Lisa, to treat trees that have become infested?

LEONDIS: Well, there are a number of chemicals that we have hopes that will be effective. There's some certain types of pesticides that will translocate through the tree. Right now, studies are being done to see how fast some of those materials will move up inside the tree all the way to the crown where they need to be effective. There's also some sprays that could be used and are systemic. But getting them up to the top of the trees is one of the problems.

CAVANAUGH: I'm going to pose this to both of you, because I don't know which one of you might feel comfortable answering this. As I know you mentioned, Lisa, a different species of palm weevil, the red palm weevil was found up in Laguna beach last year. And that really made people very, very nervous. How different is the bug up there from the one that's found down here?

LEONDIS: Well, that's a very good question. We're still trying to figure that out. The red palm weevil that was found in Laguna beach is considered the world's worst pest of palms, and it has spread through much of Europe and Asia and other parts of the world. And it is very serious. That weevil is slightly different, it's a different species, and it may not be as deadly. One of the things this weevil carries that the other one doesn't is called the red ring nematode. It's a little worm that is vectored or transmitted by this bug. That nematode alone, once a tree is infested can kill it in about five months. So that's something the other pest doesn't have. And so we're -- so far we've tested every weevil we've caught, and they have not found this nematode inside the weevil, which is very fortunate. But again both are very bad. We're just not quite as familiar with this punish species.

CAVANAUGH: This weekend a friend of mine just happened to have their palm trees trimmed, and the landscaper was way up on top of the palm tree doing what landscapers do to palm trees. I'm not quite sure what that is. Did you -- did the officials try to get the message out to landscapers to look for anything in particular when they're up there grooming these trees?

LARSEN: Yes, there were some landscape folks at this meeting, and the officials will be getting more word out to landscape professionals because you're right. They are up in the top of these trees. They just might be the first ones to notice an infestation. They can see right in the base of the palm fronds, they will be able to discover hole where is this pest has actually burrowed into the crown of the tree. And on some of the shields and such that come off of the tree, they'll be able to detect holes where the pest has drilled in event to the point where if the tree is heavily infested, there may be some oozing coming out of those holes simply because so much of the tree has been consumed and starting to rot. So they just want them to know what symptoms are so they might be able to spot those pests even if they haven't been trapped yet.

CAVANAUGH: And if a homeowner or a landscaper does find anything suspicious, what should they do, Lisa?

LEONDIS: Well, what we're doing is asking them to give the California department of food and agriculture pest hot line a call, and that number is 1-800-491-1899. And to make sure they note where they've seen it, and let us come and take a hook.

CAVANAUGH: Is the state government or the federal government, Lisa, helping us fight this pest in any way?

LEONDIS: Absolutely. The United States department of agriculture just last week found some precious scarce resources to find extended trapping throughout San Diego County, imperial and Riverside Counties, in addition to some of the other states, namely Arizona, Texas, and Florida to see really what's going on. Also Nevada. So they're helping found this effort. Without that, the state does not have any money to fund nor does the County.

CAVANAUGH: How about, Eric, would things have to get before there were some moves made toward quarantine?

LARSEN: What'll happen is the officials would have to decide that there's actually a real threat. And this test isn't quarantine, if they don't stop the movement of it, there's the risk of it spreading even faster out. And the problem with the quarantine, we have all these growers we talked about, and some of the potential rules that would be held against the growers might likely put them out of business, such as not allowing them to move the plans for months or a year after they have been treated for the pest or perhaps even having to grow their palm trees under some kind of covers. So we're very, very worried about what could happen from a quarantine. And it under lines what Lisa said earlier. We really need to know if this pest is widespread in San Diego County. So if there is a quarantine, let's say perhaps down in the border region. We would need to know whether the growers in a place like North County would be exempt.

CAVANAUGH: It sounds like one of the areas that the federal government might be able to- us, Lisa, is in working with Mexico to try to have some sort of plan to monitor and perhaps stop the infestation there. What do you think?

LEONDIS: Well, absolutely. And the United States department of agriculture does work closely with Mexican officials on many different pests. Right now, they've got some very cooperative efforts on Mexican fruit fly, Asian citrus cyllid, but those are pests that the Mexican government is also concerned about. The South American palm weevil is not on their list of concerns for one reason or another. Yet you can almost look across the border and see giant palms with their tops having fallen off. So they are experiencing some problems from this beetle. But they're only concerned about the red palm weevil.

CAVANAUGH: So if you see anything like some creepy cigars at the bottom of your palm trees, definitely contact somebody about it. And we'll have that phone number also posted on our website. I've been speaking with Eric Larsen of the San Diego farm bureau, Lisa Leondis of San Diego -- who is the San Diego agriculture commissioner. I want to thank you both for speaking with us today.

LEONDIS: Thank you.

LARSEN: Thank you.


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