South American Palm Weevil: How do they select their prey?

[Tracy]

I was doing some garden cleanup and was disturbed to see a South American palm weevil on my Ravenea julietiae.   Fortunately I had a pair of clippers in hand and was able to quickly kill it.  While examining for any signs of bores I noticed the flwer spathe was beginning to open on its first spathe.

The coincidence of timing prompted me to wonder if it was only coincidence or if something else was at work in attracting the weevil to this palm.

I also have male and female Ravenea glauca, which will be flowering again this spring.  Despite being mature enough to have flowered for a few years, they have not been prey yet.  Leucadia CIDP have been hosting and victims of the SAPW for at least 3 years now, maybe longer. 

Is their information on what attracts the weevils to their prey, such as whether scent plays a role and / or sexual maturity of the palm?

[quaman58]

Tracy, well that’s depressing. I was hoping that they took the winter off from reproducing; guess I’m wrong. Last year they took out a couple of immature Pritchardia, so I don’t think it has much to do with sexual maturity. I did read an article somewhere, that you can take for what it’s worth, that stated that freshly cut leaves somehow attracted them. So this guy‘s recommendation was to do a lot of of your larger scale pruning prior to the spring growing season. Like I say, I took it with a bit of grain of salt, but hope springs eternal. Growing palms seemed like such a simple pleasure, prior to weevils and insurance companies. 

[Phoenikakias]

For the rpw, which ravages palns in Europe, it is established knowledge, that male flowers of Phoenix spp attract the bug rather than the female ones. It is very common that after some years since the appearance of the rpw in an area, the only still surviving Phoenix specimens are in an overwhelming percentage female. On the other hand every time my female dactylifera is near in to ripening set dates, rpw pays a visit to it. I think in first case the decisive factor is called kairomone and in latter case sugar and fermentation in the fruit.

[Tracy]

55 minutes ago, quaman58 said:

Tracy, well that’s depressing. I was hoping that they took the winter off from reproducing; guess I’m wrong. Last year they took out a couple of immature Pritchardia, so I don’t think it has much to do with sexual maturity. I did read an article somewhere, that you can take for what it’s worth, that stated that freshly cut leaves somehow attracted them. So this guy‘s recommendation was to do a lot of of your larger scale pruning prior to the spring growing season. Like I say, I took it with a bit of grain of salt, but hope springs eternal. Growing palms seemed like such a simple pleasure, prior to weevils and insurance companies. 

I will take the pruning advice with a little more than a grain of salt Brett.

Now that neonicotinoid insecticide is banned in California,  does anyone have alternatives for treating palms preventivly?

[Kim]

One anecdotal comment I heard from another palm grower is that if a palm has no fibers in the trunk area, there will be no palm weevils. Theoretically growers could choose to plant only palms that have no fibrous trunks or crowns. True or false? I would love to know what people have experienced. We've all seen the photos of the fibers used to make the nest, so maybe it's true? Or maybe it's a false assumption? And it won't help those who have mature palms with fibers. 😕

[Phoenikakias]

22 minutes ago, Kim said:

One anecdotal comment I heard from another palm grower is that if a palm has no fibers in the trunk area, there will be no palm weevils. Theoretically growers could choose to plant only palms that have no fibrous trunks or crowns. True or false? I would love to know what people have experienced. We've all seen the photos of the fibers used to make the nest, so maybe it's true? Or maybe it's a false assumption? And it won't help those who have mature palms with fibers. 😕

Do Pritchardia and Ravenea have fibers?🧐

[Tracy]

50 minutes ago, Kim said:

One anecdotal comment I heard from another palm grower is that if a palm has no fibers in the trunk area, there will be no palm weevils. Theoretically growers could choose to plant only palms that have no fibrous trunks or crowns. True or false? I would love to know what people have experienced. We've all seen the photos of the fibers used to make the nest, so maybe it's true? Or maybe it's a false assumption? And it won't help those who have mature palms with fibers. 😕

Both Pritchardia and Ravenea are high on the dietary list and yes both have fibrous trunks.  CIDP are numero uno dessert items for them and ironically none of these species is native to South America.   Butia, Syagrus and Washingtonia robusta would seem to meet your fibrous trunk criteria and overlap better with this weevils original habitat yet seem to be lower on their dietary preferences from what I have observed as they move into Southern California. 

Unfortunately,  I made my palm selections before the weevil was an issue here as so many others did.

[TomJ]

In my neighborhood I have witnessed two CIDPs with overhead clear trunk taken. Each one bordering my yard.

Middle of Winter I see them everyday flying around, usually late afternoon.

This is the "catch" from 12 days in 3 traps.

[Tracy]

On 2/18/2025 at 7:00 PM, TomJ said:

In my neighborhood I have witnessed two CIDPs with overhead clear trunk taken. Each one bordering my yard.

Middle of Winter I see them everyday flying around, usually late afternoon.

This is the "catch" from 12 days in 3 traps.

Tom, please share your trap source.  I don't want to lose my Ravenea julietiae to these predators. 

[PalmatierMeg]

Here in SWFL I lost my oldest, largest Bismarckia to the FL palm weevil in 2018, 18 months after Hurricane Irma. Normally they attack compromised Sabals but they’ve developed an appetite for Bizzies. All evidence I’ve experienced, seen, studied and read about convinced me the weevils detect their victims by scent of damage, disease or other compromising conditions. Weevils are not active in winter here but come spring, dying Bizzies release adult weevils that seek out new prey. For years we cut up bars of Ivory Soap (soap, not detergent) then watered them into the crowns of our Bizzies to deter weevil attacks. The tactic worked and we lost no more palms to them. In 2022 Hurricane Ian uprooted 4 of our 6 Bizzies. We have not tried the Ivory Soap treatment since Ian but the two palms seem to be doing okay.

I won’t plant Bismarckias again. They cannot stand up to cat 4/5 hurricanes and do tremendous damage to landscapes and structures when they fall.

[Phoenikakias]

On 2/21/2025 at 1:50 AM, Tracy said:

Tom, please share your trap source.  I don't want to lose my Ravenea julietiae to these predators. 

I would not use alone such traps, because they would act completely in the opposite way, thay you hope. They will attract all nearby population of this bug, which otherwise would disperse, and with that population density it is certain that some individuals will end up in your palms and not in the bucket! Wherever traps turned out successful mean of prevention, they were serving as parts of an extended such network.

[Tracy]

On 2/16/2025 at 1:58 PM, Kim said:

One anecdotal comment I heard from another palm grower is that if a palm has no fibers in the trunk area, there will be no palm weevils. Theoretically growers could choose to plant only palms that have no fibrous trunks or crowns. True or false? I would love to know what people have experienced. We've all seen the photos of the fibers used to make the nest, so maybe it's true? Or maybe it's a false assumption? And it won't help those who have mature palms with fibers. 😕

I have continued thinking about your comment regarding fibrous trunks, particularly when walking by my Vonitra crinita.  I haven't heard anyone ever identifying the Vonitra genus as a SAPW target.  I wonder if it is because they aren't widely planted or just not frequent targets.

[gyuseppe]

to me, red palm weevil,they devoured phoenix canariensis, washingtonia filifera and robusta, trachycarpus fortunei and latisectus, brahea armata and nitida

[Than]

On 2/22/2025 at 4:56 PM, PalmatierMeg said:

For years we cut up bars of Ivory Soap (soap, not detergent) then watered them into the crowns of our Bizzies to deter weevil attacks. The tactic worked and we lost no more palms to them. 

How often did you have to apply it?

[Tracy]

A beauty and the beast greeting when i got home from work this evening. 

In the garden my male Ravenea julietiae inflorescence is opening a lovely color but no noticeable scent.  I expected a strong scent like my male Ravenea glauca inflorescence. 

As I went up the steps to the deck and house I encountered the beast.  A solitary South American palm weevil.   It didn't move so was easy to step on and kill.

[Phoenikakias]

@Tracy and @quaman58, I remember someone having posted a topic asking about early signs of a weevil infestation. Well here is an actual case concerning unfortunately a Pritchardia of mine.  Of course I have been regularly applying  insecticides preemptively and therefore hopefully larvae have not penetrated deeply and plant will eventually recover.  Plant overall looks quite pristine.

But there exist a couple alarming details for a suspicious mind. Like a drying out frond from the median set of fronds (i.e. not the oldest one) or a collapsed frond also not being the oldest one.

And I did find a dead weevil in the  base of the leaf right below the drying out one.

[quaman58]

Great pictures as always Konstantinos. On the insecticides that you’re applying, are you using them as systemic or topically?

[Phoenikakias]

6 hours ago, quaman58 said:

Great pictures as always Konstantinos. On the insecticides that you’re applying, are you using them as systemic or topically?

I use systemics from late spring to late autumn monthly. Application mode is always low pressure spraying of an ample quantity of insecticidal solution (combination of systemic and contact insecticides) directly down the apex of the crown. In winter and early spring I do not spray at all, although perhaps I also should, because root system in my climate remains during that time largely inactive. I have kept in store a small quantity of contact/vapor insecticide, just for emergency cases just like current one. It is very effective during the cold months as it practically turns whole plant to a gas chamber for besting weevils.

[Phoenikakias]

 nesting

[sonoranfans]

How they select certain plants involves the plant chemical defense systems.  All plants produce terpenes and terpenoids that function as attractants for pollinators and repellants for the pests they evolved with.  Specific terpenes/terpenoids also can be produced when a plant is sick or when it is signaling other plants about insect herbivores.  There is even one case of plants that uses scent to call in the predator of those insect herbi8vores to protect them.  Its all very complex with over one hundred terpenes that exist in the plant community many with different functions.  Sick or stressed plants is what I heard attracts palm weevils in florida but that is likely too simple a view for all cases.  Some palms may not produce the specific terpenes necessary to repel palm weevils.  There are many cases of agriculture efforts that move plants from their natural environment to another environment that has different pests and they are eaten.  If the plants are not producing the specific terpenes that protect it from that particular pest, they will be eaten.   The simplest analogy is the rock paper scissors game kids play.  If you dont have the right set of terpenes for your local pests, your plants are unprotected.  Some terpenes repel as fumigants with vapor, others that are not volatile can be contact toxins for certain pests.  

[Tracy]

On 3/25/2025 at 7:33 AM, sonoranfans said:

How they select certain plants involves the plant chemical defense systems.  All plants produce terpenes and terpenoids that function as attractants for pollinators and repellants for the pests they evolved with.  Specific terpenes/terpenoids also can be produced when a plant is sick or when it is signaling other plants about insect herbivores.  There is even one case of plants that uses scent to call in the predator of those insect herbi8vores to protect them.  Its all very complex with over one hundred terpenes that exist in the plant community many with different functions.  Sick or stressed plants is what I heard attracts palm weevils in florida but that is likely too simple a view for all cases.  Some palms may not produce the specific terpenes necessary to repel palm weevils.  There are many cases of agriculture efforts that move plants from their natural environment to another environment that has different pests and they are eaten.  If the plants are not producing the specific terpenes that protect it from that particular pest, they will be eaten.   The simplest analogy is the rock paper scissors game kids play.  If you dont have the right set of terpenes for your local pests, your plants are unprotected.  Some terpenes repel as fumigants with vapor, others that are not volatile can be contact toxins for certain pests.  

This explanation fits well with why genus and species non-native to South and Central America, which are healthy specimens otherwise,  are being attacked by the South American palm weevil here.  Thank you for those thoughts.

[MarkC]

I’m sick to my stomach with the carnage on the Phoenix genus in Florida. Central Florida’s transitional zones are especially hard hit. 

[sonoranfans]

I am just rephrasing the words of refereed research articles.  I spent about 3 years where I spent 90% of my working time researching this area of plant science.  There is really a lot out there on plant chemical defense systems, and breeding to manipulate the defense systems to a particular climate/pest.  Long term adaptation to local pests is not a theory.  Even over a shorter term a single plant has been shown to adjust its genetics (epigenetics) which can be passed onto subsequent generations.  Part of the epigenetic changes may involve production of some chemical defense system components.  But even with epigenetics the adaptation often doesn't happen fast enough to save the plant.  But with 5-10 generations the accumulated heritable changes in genetics can be more rapid than without external factors that stimulate the epigenetics.  It might be that researching the phytochemistry panels of palm species that are favored by weevils and those the weevils avoid could lead to a GRAS(human safe) weevil repellent.  Probably not enough money out there to fund it.  WH\hen I was in california I used an insecticide based on rosemary and a few other essential oils.  It smelled great, killed aphids or mites dead in seconds and was totally non toxic.  Unfortunately the big box store dropped it.   More money can be made with all those human toxic pesticides I guess.   The explosion in autism, is probably related to pesticides.

[Silas_Sancona]

9 hours ago, sonoranfans said:

  WH\hen I was in california I used an insecticide based on rosemary and a few other essential oils.  It smelled great, killed aphids or mites dead in seconds and was totally non toxic.  Unfortunately the big box store dropped it. 

Can't remember the name or who sold it but do remember what you're talking about ..and yes, it worked fairly well.. 

Imagine it wouldn't be hard for someone to put together their own formulation using  the same / other oils you could pick up at a health food store, and some soap ..or other ingredient that would help it stick ( ..for a  little while at least )

Apparently even chemical extracts from Licorice leaf may be useful in protecting plants from certain things.  Phys.org article from 2023: https://phys.org/news/2023-02-licorice-leaf-conventional-agriculture.html

Certain Bursera  sps from Mexico may also offer similar,  promising compounds as well.