Anyone have an idea about how long a pyrethrin-based bug spray would take
to work on viburnum beetle larvae? My viburnum opulus has been
skeletonised the last several years, this year I saw the caterpillar-like
beasties at work and sprayed. Two days later there were still lots
alive, I sprayed again. A day later they're still not dead but may have
stopped eating. Do I need to switch to a more noxious product?

This is a rooted cutting, now quite large, but my friend who gave it to
me is unaffected by the bugs!

-E



--
Gardening in Lower Normandy

On 14/05/15 18:54, Emery Davis wrote:
Anyone have an idea about how long a pyrethrin-based bug spray would take
to work on viburnum beetle larvae? My viburnum opulus has been
skeletonised the last several years, this year I saw the caterpillar-like
beasties at work and sprayed. Two days later there were still lots
alive, I sprayed again. A day later they're still not dead but may have
stopped eating. Do I need to switch to a more noxious product?

This is a rooted cutting, now quite large, but my friend who gave it to
me is unaffected by the bugs!

This from a 20-years old paper at Cornell Uni:
"The natural pyrethrins are contact poisons which quickly penetrate the
nerve system of the insect. A few minutes after application, the insect
cannot move or fly away. But, a "knockdown dose" does not mean a killing
dose. The natural pyrethrins are swiftly detoxified by enzymes in the
insect. Thus, some pests will recover. To delay the enzyme action so a
lethal dose is assured, organophosphates, carbamates, or synergists may
be added to the pyrethrins."

Are you using a pyrethin with a synergist (such as piperonyl butoxide)?
If not, it is quite possible that the larvae are resistant. I wonder if
a pesticide based on Bacillus thuringiensis might work.

--

Jeff

On 14/05/2015 18:54, Emery Davis wrote:
Anyone have an idea about how long a pyrethrin-based bug spray would take
to work on viburnum beetle larvae? My viburnum opulus has been
skeletonised the last several years, this year I saw the caterpillar-like
beasties at work and sprayed. Two days later there were still lots
alive, I sprayed again. A day later they're still not dead but may have
stopped eating. Do I need to switch to a more noxious product?

Fraid so if you want them dead reliably. Or you could pick them off one
by one with tweezers which would be the only true Organic(TM) way.

This is a rooted cutting, now quite large, but my friend who gave it to
me is unaffected by the bugs!

-E

A simple organophosphate contact knock down will probably still work on
them but you have to swap every couple of years to avoid resistance. I
have never had too much bother with caterpillars unless I failed to spot
them but red spider mite has been a real problem in the greenhouse.

--
Regards,
Martin Brown

On Fri, 15 May 2015 19:35:05 +0100, Jeff Layman wrote:

On 14/05/15 18:54, Emery Davis wrote:
Do I need to switch to a more

This from a 20-years old paper at Cornell Uni:
"The natural pyrethrins are contact poisons which quickly penetrate the
nerve system of the insect. A few minutes after application, the insect
cannot move or fly away. But, a "knockdown dose" does not mean a killing
dose. The natural pyrethrins are swiftly detoxified by enzymes in the
insect. Thus, some pests will recover. To delay the enzyme action so a
lethal dose is assured, organophosphates, carbamates, or synergists may
be added to the pyrethrins."


Thanks Jeff, that's useful info.

Are you using a pyrethin with a synergist (such as piperonyl butoxide)?
If not, it is quite possible that the larvae are resistant. I wonder if
a pesticide based on Bacillus thuringiensis might work.

This is a Scott's product that I use from a squeeze bottle to keep bad
aphid infestations (and they are really bad, though letting up a little
now) off the new maple growth. It's pretty "light" in that it doesn't
stop new growth or bleach out young leaves like most products do. It
turns out (closer examination, often useful!) that it does have piperonyl
butoxide, as well as Bacillus thuringiensis (serotype 3), this latter is
apparently the principle vector against caterpillars.

If on Monday I still see activity I'll try a different product.

Thanks again for the useful reply.

-E



--
Gardening in Lower Normandy

On Fri, 15 May 2015 22:30:43 +0100, Martin Brown wrote:

Fraid so if you want them dead reliably. Or you could pick them off one
by one with tweezers which would be the only true Organic(TM) way.

Ha! There are so many thousands (many per leaf, it appears) that by the
time I was done, the bush would be defoliated.

However for most actual caterpillars I do pick them off by hand, they're
quite easy to spot on smaller plants, and don't do significant damage to
larger ones.

Never had a problem with spider mites, thankfully!

-E

--
Gardening in Lower Normandy

On 16/05/2015 11:02, Emery Davis wrote:
On Fri, 15 May 2015 19:35:05 +0100, Jeff Layman wrote:

On 14/05/15 18:54, Emery Davis wrote:
Do I need to switch to a more

This from a 20-years old paper at Cornell Uni:
"The natural pyrethrins are contact poisons which quickly penetrate the
nerve system of the insect. A few minutes after application, the insect
cannot move or fly away. But, a "knockdown dose" does not mean a killing
dose. The natural pyrethrins are swiftly detoxified by enzymes in the
insect. Thus, some pests will recover. To delay the enzyme action so a
lethal dose is assured, organophosphates, carbamates, or synergists may
be added to the pyrethrins."


Thanks Jeff, that's useful info.

Are you using a pyrethin with a synergist (such as piperonyl butoxide)?
If not, it is quite possible that the larvae are resistant. I wonder if
a pesticide based on Bacillus thuringiensis might work.

This is a Scott's product that I use from a squeeze bottle to keep bad
aphid infestations (and they are really bad, though letting up a little
now) off the new maple growth. It's pretty "light" in that it doesn't
stop new growth or bleach out young leaves like most products do. It
turns out (closer examination, often useful!) that it does have piperonyl
butoxide, as well as Bacillus thuringiensis (serotype 3), this latter is
apparently the principle vector against caterpillars.

If on Monday I still see activity I'll try a different product.

Thanks again for the useful reply.

-E



Perhaps it would help to use a systemic insecticide while the
infestation is so damaging. That way, the bugs should ingest the toxin
and die. Once the shrub has hardened off a bit, it should be less
yummy. You can always revert to pyrethin for smaller outbreaks, so it
won't be wasted.
--
Spider.
On high ground in SE London
gardening on heavy clay

On Tue, 26 May 2015 14:14:09 +0100, Spider wrote:

Perhaps it would help to use a systemic insecticide while the
infestation is so damaging. That way, the bugs should ingest the toxin
and die. Once the shrub has hardened off a bit, it should be less
yummy. You can always revert to pyrethin for smaller outbreaks, so it
won't be wasted.

Hi Spider, hope you're well.

I went and looked at the shrub again this evening as it happens. It's
looking pretty good although the larvae have made some progress, it's
nothing like in previous years: the flowers are intact and looking fine
as is most of the new growth. There are still some larvae but nothing
like before, it may be that the plant will be able to outgrow them.

I sprayed a little pyrethrin underneath where I found some of the
buggers, but was trying to be careful as the Weigela next to it is
blooming and full of bees.

I think you're right though, next year I'll do a systemic early in the
season, before the larvae hatch.

cheers,

-E



--
Gardening in Lower Normandy

On 26/05/2015 18:52, Emery Davis wrote:
On Tue, 26 May 2015 14:14:09 +0100, Spider wrote:

Perhaps it would help to use a systemic insecticide while the
infestation is so damaging. That way, the bugs should ingest the toxin
and die. Once the shrub has hardened off a bit, it should be less
yummy. You can always revert to pyrethin for smaller outbreaks, so it
won't be wasted.

Hi Spider, hope you're well.

Yes, thank you. Just been away on holiday for a while.


I went and looked at the shrub again this evening as it happens. It's
looking pretty good although the larvae have made some progress, it's
nothing like in previous years: the flowers are intact and looking fine
as is most of the new growth. There are still some larvae but nothing
like before, it may be that the plant will be able to outgrow them.

I sprayed a little pyrethrin underneath where I found some of the
buggers, but was trying to be careful as the Weigela next to it is
blooming and full of bees.

I think you're right though, next year I'll do a systemic early in the
season, before the larvae hatch.

cheers,

-E


Sounds like a good plan. Hope you manage to keep them under control.
The more that survive to adulthood, the more weevils you'll have biting
lumps out of the leaves:~(
--
Spider.
On high ground in SE London
gardening on heavy clay