Here is some good, updated info regarding chemical treatments in the North East.
So far we have not seen any evidence of white grubs developing resistance to the neonicotinoids, in spite of the pattern of repeated use throughout the Northeast. However, it does appear that the “window of opportunity” for applying imidacloprid when targeting white grubs is shorter than it used to be. In other words, when Merit™ was first available, applications in early May remained active well into autumn and provided excellent control of white grubs. But imidacloprid does not appear to have as long a residual activity against grubs now. Applications of imidacloprid made before early June may not provide the anticipated level of control of the late summer grubs that we saw in the 1990s. As discussed, recent field trials suggest that chlothianidin and thiamethoxam have longer residual activity than does imidacloprid.