Chas Hurst wrote:
The crab grass slipped in on my lawn this spring. I have sprayed Ortho crab
grass killer on it with very dissapointing results. It was left over from
last year. Does it have a shelf life once opened? Are there other brands of
crab grass killer that work better?

My experience is that crabgrass killers work very slowly. And, they
are weak. I need about 3 applications, 2 weeks apart. And even then,
it takes a few weeks for the crabgrass do whither.