A week ago I planted out a lot of young module-grown brassica plants in a new bed created out of long-standing meadow land. Three days later a large number of quite big black shiny flea beetles had landed on several of the weaker plants and were fast reducing them to lacy thinness. I tried a soapy spray and diatomaceous earth but to no avail. I read that talcum powder can deter flea beetle so I liberally dusted the plants with Johnson's Baby Powder. Having hopped away, the beetles regrouped within an hour or so of my treatments and moved on to slightly stronger plants. A day or so later I resorted to a pyrethrum based spray which advertised itself as killing beetles. The attack remains unabated and it look as though within a few days the whole planting of about 70 or so plants will have been finished off.
I've never encountered flea beetle on this scale before and wondered whether there's any explanation for this sudden onslaught and whether anyone else has had similar experience

On 20/06/2019 08:24, Janet G wrote:
A week ago I planted out a lot of young module-grown brassica plants
in a new bed created out of long-standing meadow land. Three days
later a large number of quite big black shiny flea beetles had landed
on several of the weaker plants and were fast reducing them to lacy
thinness. I tried a soapy spray and diatomaceous earth but to no

Spraying diatomaceous earth isn't good for you lungs. Natural != safe.

avail. I read that talcum powder can deter flea beetle so I liberally
dusted the plants with Johnson's Baby Powder. Having hopped away, the
beetles regrouped within an hour or so of my treatments and moved on
to slightly stronger plants. A day or so later I resorted to a
pyrethrum based spray which advertised itself as killing beetles. The
attack remains unabated and it look as though within a few days the
whole planting of about 70 or so plants will have been finished off.
I've never encountered flea beetle on this scale before and wondered
whether there's any explanation for this sudden onslaught and whether
anyone else has had similar experience

I had it destroy my purple sprouting brocolli once. Leaving just the
ridges of the leaves. They did to my surprise recover after the
infestation had run its course. I was surprised how quickly they went
from normal looking to distressed. Almost as bad as gooseberry sawfly.

You may have to try a more potent insecticide or at a higher strength.
Beetles are well equipped with armour plate - they don't absorb much
insecticide through their waterproof thick chitin exo skeleton.

--
Regards,
Martin Brown

On 20/06/19 08:24, Janet G wrote:
A week ago I planted out a lot of young module-grown brassica plants in a new bed created out of long-standing meadow land. Three days later a large number of quite big black shiny flea beetles had landed on several of the weaker plants and were fast reducing them to lacy thinness. I tried a soapy spray and diatomaceous earth but to no avail. I read that talcum powder can deter flea beetle so I liberally dusted the plants with Johnson's Baby Powder. Having hopped away, the beetles regrouped within an hour or so of my treatments and moved on to slightly stronger plants. A day or so later I resorted to a pyrethrum based spray which advertised itself as killing beetles. The attack remains unabated and it look as though within a few days the whole planting of about 70 or so plants will have been finished off.
I've never encountered flea beetle on this scale before and wondered whether there's any explanation for this sudden onslaught and whether anyone else has had similar experience

Welcome to the future.

There are no effective chemical insecticides, because they've all been
removed from the market (at least for amateur use). I'm not advocating
wholesale, unlimited use of chemicals - I have had many unopened or
little-used bottles of insecticides over the years as I find many
attacks are self-limiting. However, I don't grow food crops, so it
doesn't matter if an ornamental gets a bit unsightly for a time, or I
just give up on it and grow something else. But food crops are another
matter; sure there are bioinsecticides coming one (you might find a bit
of googling on Beauvaria bassiana of interest), but they aren't cheap,
sometimes don't work well at low temperatures, and resistance is on the way:
https://www.frontiersin.org/articles/10.3389/fpls.2015.00381/full

I find a certain irony - at least with what you have been trying to grow
- that the Greens policies are ensuring there won't be any greens for
you to eat.

--

Jeff

On 20 Jun 2019 00:24, Janet G wrote:
A week ago I planted out a lot of young module-grown brassica plants in a new bed created out of long-standing meadow land. Three days later a large number of quite big black shiny flea beetles had landed on several of the weaker plants and were fast reducing them to lacy thinness. I tried a soapy spray and diatomaceous earth but to no avail. I read that talcu
m powder can deter flea beetle so I liberally dusted the plants with Johnson's Baby Powder. Having hopped away, the beetles regrouped within an hour or so of my treatments and moved on to slightly stronger plants. A day or so later I resorted to a pyrethrum based spray which advertised itself as killing beetles. The attack remains unabated and it look as though
within a few days the whole planting of about 70 or so plants will have been finished off.
I've never encountered flea beetle on this scale before and wondered whether there's any explanation for this sudden onslaught and whether anyone else has had similar experience

Used to use Derris dust but that's off the market now, have been
thinking for a long while that amateurs wont be able to grow much soon.
So distressing when a whole crop gets devastated after all your hard
work.
There is a gap in the flea beetle life cycle which normally
allows the plants to recover and grow through it but it's not always
the case.

--
Regards
Bob Hobden

In article ,
Jeff Layman wrote:

I find a certain irony - at least with what you have been trying to grow
- that the Greens policies are ensuring there won't be any greens for
you to eat.

That is nonsense. Another solution that works is netting - I use it
because our 'oriental greens' were getting too full of shotholes to
be worth (us) eating. But I don't use it on kohl rabi, broccoli or
kale. I do use toxic chemicals, but do my damnedest to avoid doing
so on food crops or those visited by bees.

Flea beetles are very rarely more than a nuisance, and I also find
it a bit puzzling - but the solution is to tackle a cause rather than
covering the plants with toxic chemicals. Which first means finding
one or more of the causes for such an infestation. It is possible
that there was a thriving population in the meadow, because they live
in Cruciferae, and they all hatched at the wrong time. If that is so,
the solution is to grow something else for a year, and then net the
brassicas, at least until they are properly established.


Regards,
Nick Maclaren.

On 21/06/19 11:29, Nick Maclaren wrote:
In article ,
Jeff Layman wrote:

I find a certain irony - at least with what you have been trying to grow
- that the Greens policies are ensuring there won't be any greens for
you to eat.

That is nonsense.

In what sense? This is from the section on "Sustainable Farming" in
their policies on "Food and Farming" at
https://policy.greenparty.org.uk/fa.html

"FA638 The Green Party will ban the use of the most harmful substances
used in the treatment of soil, crops and animals and support a
progressive reduction in the use of synthetic fertilisers and pesticides
which do not meet organic standards, through the promotion of benign
forms of pest and disease management and maintenance of optimal soil,
plant and animal health. (See also CY525)"

What pesticides meet organic standards? Even pyrethrins are toxic to
many forms of life other than pests. Derris went years ago. And the
organic standards can be set so that nothing meets them.

And from the "Food Safety" section:
"FA313 Levels of pesticide and drug (including antibiotics) residues in
food will be closely monitored and programmes put in place to eventually
eliminate these residues."

I wonder what they will consider to be the level at which the residues
will be eliminated/? The level of detection? Sub-attograms per gram?

Even before the agricultural use chemicals go completely, there will be
none for amateur use.

Another solution that works is netting - I use it
because our 'oriental greens' were getting too full of shotholes to
be worth (us) eating.

I have no doubt that netting works, but what happens if some flea
beetles happen to get in? What is their reproduction rate?

But I don't use it on kohl rabi, broccoli or
kale. I do use toxic chemicals, but do my damnedest to avoid doing
so on food crops or those visited by bees.

I wouldn't argue with that, because, in general, amateurs grow food
plants "for fun". If our crops fail we go round to the greengrocer or
supermarket to replace them. But on a commercial scale it's a different
matter. Already some farmers have given up growing oilseed rape because
of flea beetle, and if other pesticides go other food crops will be at
risk. Our escape policy of going round to a shop to get food just won't
work, because they won't have the crop either. That's what you get with
an extremist policy. I am happy for pesticides to be used as little as
possible, but I want there to be a stockpile of two or three pesticides
with different modes of activity if (when?) the organic methods fail.
But that is not what the Greens want. They want them gone, and gone
forever.

Flea beetles are very rarely more than a nuisance,

Not to the OP - "it look as though within a few days the whole planting
of about 70 or so plants will have been finished off".

and I also find
it a bit puzzling - but the solution is to tackle a cause rather than
covering the plants with toxic chemicals. Which first means finding
one or more of the causes for such an infestation. It is possible
that there was a thriving population in the meadow, because they live
in Cruciferae, and they all hatched at the wrong time. If that is so,
the solution is to grow something else for a year, and then net the
brassicas, at least until they are properly established.

Sorry, but that's wishful thinking. They *will* reappear; maybe not next
year, or the year after, but they'll be back in force to decimate your
crop. Why should they be any different from other insect pests such as
locusts, which we are very lucky to not have here (but with global
warming, who knows?), and which reappear at regular intervals?

One other point. Where will your seeds come from if the seed-crop plants
that produce them have been killed off?

--

Jeff

In article ,
Jeff Layman wrote:

What pesticides meet organic standards? Even pyrethrins are toxic to
many forms of life other than pests. Derris went years ago. And the
organic standards can be set so that nothing meets them.

And they can be set so that nothing can survive, not even the humans
eating the product.

There are more than you realise, soft soap for one, though it's not
useful in this case. Personally, I would allow nicotine again!

Another solution that works is netting - I use it
because our 'oriental greens' were getting too full of shotholes to
be worth (us) eating.

I have no doubt that netting works, but what happens if some flea
beetles happen to get in? What is their reproduction rate?

You get minor damage. Live with it. I posted what I said for good
reason - a solution targetted to the pest's life-cycle is going to
work my better than merely making the plant toxic. No, they do not
reproduce that fast, and summer greens are cropped after a fairly
short period. As I said, once a brassica is established for winter
use, significant damage is very rare.


Regards,
Nick Maclaren.

Avoiding controversy and keeping to practicalities I would say that well over half of the young plants have been lost. I noticed elsewhere though that flea beetles were crowding onto the mesh covering brassicas but were unable to get through. So I think the treatment has to be mesh rather than netting. I had used butterfly netting on these plants rather than enviromesh. Replacing the netting with mesh at least prevented further waves of flea beetles.
For some reason there seem to be a lot more this year than usual at least in my patch. I wonder whether they have come off the nearby rape fields in greater quantities than normal.
Janet G

On 29 Jun 2019 16:26, Janet G wrote:
Avoiding controversy and keeping to practicalities I would say that well over half of the young plants have been lost. I noticed elsewhere though that flea beetles were crowding onto the mesh covering brassicas but were unable to get through. So I think the treatment has to be mesh rather than netting. I had used butterfly netting on these plants rather than e
nviromesh. Replacing the netting with mesh at least prevented further waves of flea beetles.
For some reason there seem to be a lot more this year than usual at least in my patch. I wonder whether they have come off the nearby rape fields in greater quantities than normal.

Interestingly a couple of years ago we went to an outdoor event next to
some Rape fields and not thinking my wife wore a bright yellow tea
shirt. She was covered in the things. I recon those yellow sticky pads
you get for the greenhouse would do for lots.
--
Regards
Bob Hobden

In article ,
Janet G wrote:
Avoiding controversy and keeping to practicalities I would say that well
over half of the young plants have been lost. I noticed elsewhere though
that flea beetles were crowding onto the mesh covering brassicas but
were unable to get through. So I think the treatment has to be mesh
rather than netting. I had used butterfly netting on these plants rather
than enviromesh. Replacing the netting with mesh at least prevented
further waves of flea beetles.

In my case, it was pak choi etc. eaten to the point of being inedible
by humans - i.e. there was nothing left except dry threads! Now I
use mesh, they have holes in but are still fit to eat.

For some reason there seem to be a lot more this year than usual at
least in my patch. I wonder whether they have come off the nearby rape
fields in greater quantities than normal.

Very likely. There was one year when aphid clouds impeded visibility
enough to cause traffic accidents, following harvest.


Regards,
Nick Maclaren.