A google search didn't show the effective life of Dimension, but most
pre-emergents only work for 2-6 months. My guess is that whether you
de-thatch this fall or not you'll need to re-apply dimension next spring. If
you de-thatch in the Spring, you'll need to apply Dimension after
de-thatching, which could be too late to prevent crabgrass germination.

KB


"JL" wrote in message
...
I had a section of lawn that had crabgrass in years past.
This spring I used a product that contains Dimension (thanks ahlg).
It worked great. I have some stray crabgrass plants
that I deal with spot treatment.

Will I ruin my Dimension for next year if I de-thatch
this fall/next spring? That is, how long do I have to
wait for the crabgrass seeds to finally die before I'm
able to dethatch?