What is the key differentiator in peak flight timing between the Winter Moth and the Bruce Spanworm?

The Winter Moth flight peaks later (Nov-Dec) than the Bruce Spanworm flight (Oct-Nov).

Accurate location assessment requires distinguishing the Winter Moth from the similar Bruce Spanworm (*Operophtera bruceata*), as treatment timings might vary. The table provided outlines clear differentiators, most notably the timing of the adult flight period. The Winter Moth’s flight is concentrated later in the season, spanning late Fall/Early Winter, specifically noted as November through December. In contrast, the Bruce Spanworm’s flight activity generally peaks earlier, occurring in October through November. If significant activity is noted peaking in October, the Spanworm is likely the larger component, whereas December activity strongly indicates the presence of the Winter Moth.