On 25/05/2011 20:11, Jake wrote:
On Wed, 25 May 2011 19:31:30 +0100, Mike Lyle
wrote:

The red lily beetle have been at work, and I'm not completely mobile
at the moment. So far, my lilies haven't had a full-scale assault, but
my beloved snake's-head fritillaries have been copping it a bit. I've
caught a few and squashed them, and gone over the leaves for eggs and
larvae; but it occurs to me that the fritillaries are pretty near over
anyway, with seed pods fairly well developed and many leaves looking
tired. So I'm going to cut them off and dispose of the little sods'
food supply. How sensitive are snake's-heads to cutting down before
they die down naturally?

I've always understood it to be essential to let the foliage die back
naturally (though I lop the heads off) - one reason I don't grow them
in grass is the advice not to mow until the foliage has had it. I've
checked my reference books and any that talk about post flowering
treatment refer to not cutting the foliage until summer when it has
completely died back.

I believe this is down to the fact that the plant effectively eats its
bulb during the flowering period and then starts to create a new bulb
and so needs the dying foliage more than, say, a narcissus or a tulip.

Lily beetle are the main obstacle to my going fully organic - I use
Provado Ultimate Bug killer on lilies now. As long as you're careful
when you spray (it kills ladybirds, bees etc as well) it's then
absorbed by the plant and will continue to kill the little red things
once they chomp a bit of leaf. Alternatively, Toby Buckland says that
he's found that a product called SB Plant Invigorator (also sold by
QVC under the Flower Power brand) kills lily beetle among other
nasties and it's organic.

Note that the name Provado Ultimate Bug Killer is used for several
products. Those that contain imidacloprid alone as the active
ingredient are, in my opinion, inactive against lily beetle. To deal
with that pest you will have to use the aerosol can, which contains
methiocarb as well as imidacloprid. Even then, after a few weeks it
will be back, and you will have to spray again.

--

Jeff