Sempervivum forum: Weevils in my Sempervivum

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Name: Lynn
Dallas, OR (Zone 8b)
Charter ATP Member Garden Sages I helped plan and beta test the plant database. I helped beta test the Garden Planting Calendar I was one of the first 300 contributors to the plant database! Plant Database Moderator
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valleylynn
Nov 29, 2017 11:05 AM CST

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tcstoehr said:It's been sunny, t-shirt weather this morning. Now it's dark as night and heavy showers thundering down.

I wanted to ask about something. I had a sizable Heuf come down with some rot a week or two ago. Looking at the plant, part of it was kind of sad looking. Poking a finger underneath revealed a mushy spot. The plant broke into three pieces as I messed with it. The largest section remains alive and well in the ground. Another piece is in the green house. The remaining mushy section had tiny little maggots crawling around inside it. Anybody see this in any of your semps?
I don't know if the rot attracted some dead-flesh-eating flies, or these maggots themselves were the cause.
Possibly baby crane-fly larvae? If so then I've saved myself some grief down the road.
The same thing happened on a different semp earlier. I caught these both pretty early and the damage was minimal.
If I ever see them again I'll take a picture. It will be difficult cuz they're way small.


LivingWreaths said:
Yes, I have had this happen. For me the grubs are not from crane fly. They are from my worst enemy, the WEEVIL!
yes, evil-weevil is the culprit at my house, and I battle it all year round. When I notice my Semps, or any of my plants are not growing as much as they should, I begin to suspect the evil weevil.
You won't necessarily notice any above-ground damage from the adult Weevil because it may be living in a different plant nearby. Then they lay their eggs everywhere and the grubs eat your roots from the inside out. In the winter time when it starts to rain, my Weevil damaged semps will turn mushy yellow and I pull them out of the ground and they have no roots attached(or hardly any)... prior to the rains they will look perfectly normal other than they haven't grown any bigger. Or they put out a ton of babies, but the central semp has no roots. Weevil larvae have a symbiotic relationship with a nasty bacteria that aids in turning the roots to Mush so they can eat it easily. Even after the larva are gone, this bacteria will continue to rot The Roots. So the damage keeps on giving... then other tiny worms come in to eat up more of the mush (but they arent the problem...they're just cleaning up the mess).


dirtdorphins said:Eeek Blinking
Just looked up the weevils and I've seen a few adults now and then...
I'm blaming all my potted plant deaths on these guys now (rather than my poor tending skills aka negligence)
but seriously, I'm gonna have to investigate the roots more closely next time!


valleylynn said:Well this is very interesting. Tiffany how to you get rid of your evil weevils?


tcstoehr said:OK... that's two votes for the weevil. I hadn't even thought that weevils had a larval stage. Shows what I know.
After reading Jo Ann and Tiffany's remarks I now consider this Vine Weevil to be a highly likely suspect. Perhaps I should have him brought in for questioning.
At the very least I should have put those larvae under high magnification to see if they have a distinct head or not. No discernable head/mouth/eyes would lead me to think it was a fly maggot and not a beetle or weevil grub.
This may also be the reason why my colony of 'Ohio Burgundy' was found to be largely devoid of roots this past Spring. I also discovered a Heuf earlier this year that was growing great but began to show signs of stress. Lifting it showed a complete absence of roots although the crown and leaves were OK. I've potted that one up in my greenhouse and it has grown vigorous new roots.
Seems like this weevil may infect either the roots or the crowns of semps.
If it ain't one thing... it's another.


LivingWreaths said:

I use Imidacloprid or beta-cyfluthrin, in systemic form.
During the height of the adult activity-Midsummer-I go out at night and pick off as many as I can. They like to play dead so make sure you crush them. Weevils only come in female form, so every Weevil can lay a potential of 400 eggs. That adds up to a lot of damage! They allegedly go through two full life cycles a year. When Weevils lay their eggs in the fall, the Grubs winter over, all the while eating the "bejeebers" out of your plant's roots-- and you won't see the damage until the Spring! Thus you would never suspect the evil weevil.
Weevils can easily get to outbreak status and I found that they live at my neighbor's house and walk over to my plants at night! Stinkers!
The weevils almost took down an 18 foot palm tree we have in our front yard, simply because the grubs love to eat the root system. The palm tree had stopped growing for a long time and as soon as I treated with the above, tree started growing again. We almost lost the tree!


Now some blogs recommend parasitic nematodes that destroy the weevils/their grubs in a zombie apocalypse type of way.... when researching the specifics you will find that these nematodes need exact temperature, weather (atmospheric pressure, day light hours, humidity, etc) conditions in order to do their dirty work. I calculated that there are EXACTLY TWO-37 MINUTE PERIODS of time (one in Spring, one in the Fall) in the Pacific Northwest at which these conditions occur. Also, the nematodes seemed about as effective as changing the salinity of the ocean by adding a cup of tap water.
I'll let you decide if your time energy and financial resources are worth it.

One thing is for certain, you must be diligent in getting rid of these little 'buggers (I only used one pun this whole post).'
Also, the gardening oils and things like that I haven't found to work only because Weevils have such thick armor. But a spray application of the above two chemicals does work in conjunction with a systemic. If you're finding them on your fruits and vegetables then spray pyrethrin and get out at night and start picking these evil weevil babes off your plants. And make sure your non-food plants nearby are well treated so Weevils don't use them as a crashpad to get to your veggies. BTW, Weevils hide in the dirt during day so if you have them in ur pots look around the edge just at dirt surface. You'll see them taking their siesta and if you touch them they will play dead. Don't believe their lies! Crush them!


Okay, I just looked up what a weevil looks like: https://www.google.com/search?...
I have found these out in the garden once, on my Penstemon pinifolius. I didn't know what it was, but I squashed it because it appeared to be feeding on the plant. It was feeding on the seed pods.
I will start really watching for this problem. This really speaks to sending offsets bare root. I know here in the PNW most nurseries treat their potted plants for this type of problem, but coming from in ground/outside I think we all need to take precaution.
Tiffany, thank you so much for all the information.
Name: Lynn
Dallas, OR (Zone 8b)
Charter ATP Member Garden Sages I helped plan and beta test the plant database. I helped beta test the Garden Planting Calendar I was one of the first 300 contributors to the plant database! Plant Database Moderator
Forum moderator I helped beta test the first seed swap Million Pollinator Garden Challenge Celebrating Gardening: 2015 Plant and/or Seed Trader Garden Ideas: Master Level
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valleylynn
Nov 29, 2017 11:42 AM CST

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JungleShadows said:Lynn,

I've never had much problem with weevils in the ground except for an area that I filled with potting soil. That bed had it bad one spring but a treatment with a pyrethroid insecticide knocked them out. They seem to REALLY like a very fluffy peaty soil mix. Now I use what the local nursery calls "premium perennial bedding mix". It has NO peat and the semps seem to really like it. Better yet the weevils DON'T!
Kevin

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