Ken from Columbia, Sc writes
Merit and other products containing imidacloprid should be applied prior to egg hatch of the target pests, which means the product is typically applied in the spring/early summer. Later in the season folks typically use Dylox as a curative treatment. We recommend you check with your local cooperative extension office to see what they recommend you apply this late in the season in your region.
Answer last updated on: 11/04/2012