Devil's coach horse beetle feasting on dying howeas?

[Rivera]

I have a clump of four young Howea forsteriana in the ground. Two are healthy and pushing new growth. I just pulled brown spears on the other two and found the bad leaves to have a small infestation of beetles and what I presume are beetle larvae. They're tiny, Argentine ant-size or smaller. 

I believe these are larval and juvenile death's coach horse beetles, which we have some of around the garden. They don't generally seem to be a horticultural pest and just tend to lurk around decaying matter, which is maybe what the larvae eat in the absence of a flesh host. 

Can anyone confirm or deny the identity of this insect based on the photos?

I will try to save the two affected howeas, but I believe they will most likely die. 

[Silas_Sancona]

5 minutes ago, Rivera said:

I have a clump of four young Howea forsteriana in the ground. Two are healthy and pushing new growth. I just pulled brown spears on the other two and found the bad leaves to have a small infestation of beetles and what I presume are beetle larvae. They're tiny, Argentine ant-size or smaller. 

I believe these are larval and juvenile death's coach horse beetles, which we have some of around the garden. They don't generally seem to be a horticultural pest and just tend to lurk around decaying matter, which is maybe what the larvae eat in the absence of a flesh host. 

Can anyone confirm or deny the identity of this insect based on the photos?

I will try to save the two affected howeas, but I believe they will most likely die. 

Tough call.. at least on the first shot. iNat pictures of juveniles look a little different. 2nd one may be something like Narcissus Fly / other detritus- consuming Fly. since i larval stage pictured is a Maggot. Beetle grubs will generally look Caterpillar-like / have tiny legs.

[Rivera]

41 minutes ago, Silas_Sancona said:

Tough call.. at least on the first shot. iNat pictures of juveniles look a little different. 2nd one may be something like Narcissus Fly / other detritus- consuming Fly. since i larval stage pictured is a Maggot. Beetle grubs will generally look Caterpillar-like / have tiny legs.

Thank you. I may have misidentified and assumed a relationship amongst the buggers that does not exist.  Though I couldn't smell the rot myself, the bugs nearly always seem to find compromised plant tissue before I do. 

[Silas_Sancona]

9 minutes ago, Rivera said:

Thank you. I may have misidentified and assumed a relationship amongst the buggers that does not exist.  Though I couldn't smell the rot myself, the bugs nearly always seem to find compromised plant tissue before I do. 

Not 100% certain of this, but, since they are in the Rove Beetle family, i think Devil's Coach eat things like fly larvae, snails / slugs ..other bugs.. So the one you found  ..same sp. or different, may have been prowling around looking for the maggots / other soft bodied bugs hanging out in the decaying plant material, rather than joining the buffet themselves..

I guess with bugs, decomposers esp, they can small decaying stuff / chemicals emitted from stressed out plants well before we notice it.

..Kind of like smelling someone BBQ'ing several blocks away when it is windy ..or the smell of Garlic in the air being drawn north 24 miles from Gilroy on a humid day when they're out harvesting. Always made me hungry / ready for the festival lol.

[PalmsandLiszt]

16 hours ago, Rivera said:

I believe these are larval and juvenile death's coach horse beetles, which we have some of around the garden. They don't generally seem to be a horticultural pest and just tend to lurk around decaying matter, which is maybe what the larvae eat in the absence of a flesh host. 

15 hours ago, Silas_Sancona said:

Not 100% certain of this, but, since they are in the Rove Beetle family, i think Devil's Coach eat things like fly larvae, snails / slugs ..other bugs.. So the one you found  ..same sp. or different, may have been prowling around looking for the maggots / other soft bodied bugs hanging out in the decaying plant material, rather than joining the buffet themselves..

This is quite right; rove beetle larvae are active carnivores which run around and consume prey like the adults. They are not worm/grub-like:

The white larva in the photo definitely looks like a maggot (dipteran) of some sort, although this is a huge field. It might be eating your palm, it might be eating decaying matter (probably most likely) or it might even be carnivorous as many hover fly larvae are. The Devil's coach horses certainly won't be eating the palm, however, and might well be eating the fly larvae. If I were you, I'd probably try to get rid of the maggots but leave the beetles if possible.
If they are eating detritus, chances are the spears were in bad shape for an unconnected reason and the larvae are just a symptom attracted by the decay. A fungicide might do more good than an insecticide.

[Rivera]

38 minutes ago, PalmsandLiszt said:

This is quite right; rove beetle larvae are active carnivores which run around and consume prey like the adults. They are not worm/grub-like:

The white larva in the photo definitely looks like a maggot (dipteran) of some sort, although this is a huge field. It might be eating your palm, it might be eating decaying matter (probably most likely) or it might even be carnivorous as many hover fly larvae are. The Devil's coach horses certainly won't be eating the palm, however, and might well be eating the fly larvae. If I were you, I'd probably try to get rid of the maggots but leave the beetles if possible.
If they are eating detritus, chances are the spears were in bad shape for an unconnected reason and the larvae are just a symptom attracted by the decay. A fungicide might do more good than an insecticide.

Thanks, much appreciated. 🙏 Clearly not beetle larvae as I first thought. 

The two affected palms are getting H2O2 treatment and packed with paper towel to absorb the water afterwards. 

[JLM]

On 5/14/2023 at 4:53 PM, Silas_Sancona said:

Not 100% certain of this, but, since they are in the Rove Beetle family, i think Devil's Coach eat things like fly larvae, snails / slugs ..other bugs.. So the one you found  ..same sp. or different, may have been prowling around looking for the maggots / other soft bodied bugs hanging out in the decaying plant material, rather than joining the buffet themselves..

I guess with bugs, decomposers esp, they can small decaying stuff / chemicals emitted from stressed out plants well before we notice it.

..Kind of like smelling someone BBQ'ing several blocks away when it is windy ..or the smell of Garlic in the air being drawn north 24 miles from Gilroy on a humid day when they're out harvesting. Always made me hungry / ready for the festival lol.

Yeah, just learned about blow flies in a forensic science class, they can basically smell death from 1-2 miles away, within just mere minutes following death. The BBQ analogy is very precise.

[Silas_Sancona]

32 minutes ago, JLM said:

Yeah, just learned about blow flies in a forensic science class, they can basically smell death from 1-2 miles away, within just mere minutes following death. The BBQ analogy is very precise.

It may sound gross to some, but some of the most insightful " Ah Ha " things i've learned about how insects ..and some other critters figure out where the " clean up " jobs are was by observing flies on dead things..

The succession -of species-,  ...who arrives first, ...and who gets what scraps might be left at the very end..  it's all an intriguing and valuable process to learn about., albeit stomach churning at times also..   Always found Forensic Entomology fascinating since again, there is a process and each type of insect noted at different times ..can provide valuable information to someone investigating..

As far as smell goes, from the perspective of " nature's janitors ",  last dead thing i came across out in the desert wasn't first noted by smell, it was watching Turkey Vultures which kept flushing from behind a bunch of cacti / Palo Verde not far from where i was standing.   Flies, various Reptiles, or mammals picking up on the scent of the deceased is one thing ..how birds like Vultures / Caracara, or any other Carrion- feeding raptor / other birds, can pick up on a, ...ahem, " buffet ",  while passing several thousand feet above the same ahem, " buffet "   is a solid testament to the wonders of nature.

 

[Rivera]

Update:

Had a chuckle looking back at this. 

All four Howea are alive and growing.

One of them pushed out a baby frond (they were planted in the shade during the winter and were badly sunburned following increased exposure).

The rest of the new leaves coming in look pretty normal, though they'll probably still look rough on the whole for a couple years.