On Sun, 26 Sep 2010 01:26:31 -0700 (PDT), harry
wrote:

On 26 Sep, 08:37, "bm" wrote:
Recently I found that over night a patch in the centre of my lawn had been
'chewed up' Examining the mess I noticed that there were a number of white
larvae and also there was a weed that looked like grass but had a long stem
and spread by layering.
A neighbour had the same and said that it was caused by crows at dawn
digging for the larvae which he thought was the larvae of slugs or snails
By coincidence this patch coincided with the area where moles had previously
dug their tunnels
I have scraped as much of this weed as possible but I think some of the
roots remain
What weed killer should I use to kill this weed?
Blair

Slugs and snail don't have larvae, only insects. Probably crane fly
larvae. They eat the roots of grass. Birds will eat them given chance
and scrat about looking for more. More likely to be a headgehog or
other small mammal by the sound of the damage..
If you have a non-grass weed you can use a broadleave weedkiller.
There are lots of lawn weedkillers out there.

But you're going to have a problem with a lawn weedkiller - they need
foliage to be absorbed by and if you've scraped most of it away then
the weed stuff won't be so effective at getting to the roots that
remain. Weedkillers that soak into the ground and kill the roots that
way will also kill any grass roots they touch and prevent anything
(including grass) growing in the area for months.

If the ground has been "chewed up" then it won't hurt to use a hand
fork to get in a bit deeper and get all the roots you can find out
by hand.

Next you want to identify the larvae for certain - Harry's almost
certainly right but as you have a specimen or two, type "crane fly
larvae" into your search engine and you'll find something with
pictures to compare. If they are, they will damage the lawn through
the winter and spring by eating the grass roots (as well as attracting
foragers). You can deal with them using nematodes if you're organic
(Rolawn sell specific crane fly nematodes) or with Provado Lawn Grub
Killer.

Then get some suitable grass seed and reseed the damaged area - better
to get grass growing there than leaving it bare for more weeds to get
in. Put some net over the seeded area to keep the wildlife off while
the grass grows.