As others have pointed out, a lot depends on the user and following
directions. To be effective, the granular herbicide needs to hit a
wet weed and stick. It also needs to be applied at the right rate.
The herbicide is only affective against most broadleaf weeds. So, if
it's crabgrass that's the problem, it's not going to work. Also, this
is slow release, so burning should not be a problem with this product,
unless you apply it beyond the directed rate.
I'm not a big fan of the Weed n Feed type products. They can be useful
if the lawn is a complete mess with a lot of weeds. But for a
reasonably maintained lawn, spot weed control with a small tank sprayer
is more effective and better for the environment. You get maximum
effectiveness with minimum herbicide by delivering it where it's
I also would not be fertilizing in the northeast at this time of year.
Nitrogen plus hot weather tends to promote disease and fungus.