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NC State Extension

Control Based on Treatment Windows

Windows of Opportunity — Not Calendar Sprays

Since the late 1970s, most Fraser fir Christmas tree growers in western North Carolina have focused on applying pesticides in the spring to control the balsam twig aphid. Most growers used Di-Syston 15G for twig aphid and mite control and Lindane every 2 to 3 years in the summer for balsam woolly adelgid control.

Through the years, many things have changed. Lindane and Di-Syston have been replaced with newer products. New pests have developed too — first rosette bud mites, then rust mites, problems with Cinara aphids, and elongate hemlock scale. Growers discovered that when they treated in the fall for Cinara aphids, there were fewer problems with twig aphids the following year. The spring treatment window became less important.

Now that there are more pests and more choices, it’s become harder than ever to know what’s best to do to control pests. The following pages summarize for each treatment window the stage of the pests, advantages and disadvantages of treating during that window, and what pesticides are effective against which pests during that timeframe.

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