I showed this modified color wheel at the North Carolina Christmas Tree Association meeting in Boone on Thursday, March 1.
We use this wheel to show Christmas tree growers when you can treat for the various pests. Based on what we were seeing last year, I modified the timeline for the elongate hemlock scale. We've been seeing good control from mid May through August. Spraying before bud break and later in September probably won't work as well, though it may fit better into your spray schedule -- hence the dotted pink line. If you don't have twig aphid control in market size trees, you might need to treat before bud break. The fall treatment window in September is better for protecting natural predators as well as Cinara aphid control. We'll continue to evaluate control during those treatment windows in 2012, so if you do treat then, let us know so we can follow how well its been working.