digger said:

A few years ago my lawn became distressed when workmen took too long
in putting up our aluminum siding. Since then every August and
September, grubs invade our lawn. I re-seed in the spring only to get
the thinning and brown patches start all over again in late summer.
Chemicals are out of the question. Does anyone have advice on a way
to protect my grass, but get rid of the grubs?

Assuming you are talking about northern (cool season) lawn grasses...

Water and fertilize through the summer rather than letting it go dormant.
If you can keep it actively growing, the grass can outpace the grubs (this
is per the MSU extension service). The beetles are less likely to lay eggs
in a well-watered turf. Once the turf is back thick and full again, you maybe
can ease back on the summer watering -- but during *really* dry spells make
sure it gets watered at least one inch every three weeks even if you've let
it go dormant for the summer.

I remember reading about research using a finely spiked machine running
over the turf in late summer to skewer grubs. Don't know if that ever proved
practical...
--
Pat in Plymouth MI ('someplace.net' is comcast)

Any technology distinguishable from magic is insufficiently advanced.
(attributed to Don Marti)