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