Down here along the coast (CT), no problems so far. I think you are local, so I would assume it was all watered in, because of the rain we had all season. We put ours down a little bit later - 3rd application, after 2 pre-emergents, so it was going down while the grass was really growing well. Did you put it down too early, or during that short hot/dry spell we had early in the season?
I have had lawns treated with merit sandwiched between bad lawns with nasty infestations. For the last few years its been like there is an invisible fence.
I use MachII, but a customer put down GrubX (Merit) and had some damage, not severe, but there none the less.
Another customer has one of the larger Co's in the area treat his lawn. I have been trying to get him for years. I stopped to cut one afternoon, and the tech was there. I asked what he was applying, he replied" grub control". I didn't get anything further from him.
Well, this lawn suffered big time. The critters are a diggin'. If I can't sell him after this, I never will be able to.
Steven, I would check that all problem properties were not in the same batch of spray. Can always have a mixing error. If you are sure of calibrations, I would check with the Bayer rep for your area.
When I have had problems with chemicals in the past, I found the manufacturer reps to be the best source of resolution. It is often a simple answer that you never think of.
Steven, An important factor in successful grub control is application timing,rate and pest being controlled. If Merit
is applied to early there will be not enough residue for effictive control. Bayer is recommending applying Merit at the highest rate. Merit should be watered in very soon after
the initial application v/s Mach 2. Was the grubs found checked to see what grub it was? If the grub was a masked
cheafer you may have missed the window. I've used Merit for the 5 years or so and have had excellent results. No plans
on changing products any time soon. By the way I use granular fertilizer w/ Merit.
Jaclawn, you said that a customer used some GrubX. The formulation of that product changed this year in my part of the country (midwest). It used to be the same active as merit but now is that same as MachII. I noticed this at the hardware store one day. I use merit and machII on a rotating basis now. Half my yards get merit one year mach II the next, the reverse next year. I say kill'em all let god sort them out