Hi, I had a section of new lawn die off last year and this week I've
noticed several brown patches and a lot of crane flies in the house -
maybe half a dozen each night.

I put a groundsheet out last night and had a look under it this morning
but I couldn't see any grubs. There were however a few dead crane
flies so I suspect I have a leatherjacket infestation. One brown patch
is quite bad and will need reseeding. The other pathes aren't too bad
at the moment.

I was thinking about using nematodes but I'm unsure of when is the best
time. The crane flies first starting appearing at the beginning of
this week so should I wait for them to lay eggs or apply the nematodes
now?

It's only a small lawn maybe 25 sqm so I don't mind using the black
plastic "pick them up" method if it works.