Pheromone surveys
In Massachusetts, for each year from 2007-2018, adult male moths were
collected using pheromone-baited lures (Great Lakes IPM, Vestaburg, MI;
Elkinton et al., 2010, 2011) hung in plastic bucket traps (Gempler’s
Inc., Janesville, WI) at points along the Massachusetts transect (Figure
1). These included 49 unique localities; however, due to factors such as
road construction, early-season snow, ice storms, vandalism, and mouse
predation, an average of 22 trap localities (± 1.5) were sampled each
year, with a minimum of 16 traps in 2015 and a maximum of 32 traps in
2017 and 2018. In addition, after 2009, we discontinued monitoring traps
close to the Boston Metropolitan area (T21-T25) in an effort to conserve
survey resources because these traps were entirely composed of winter
moth individuals (Elkinton et al., 2014). From 2007-2016, moths were
collected from traps twice during the sampling period (late November
through early January), coinciding with observations of male moth
flight. In 2017, moths were collected during the same period weekly, and
in 2018, traps were sampled bi-weekly. For the Connecticut transect
(Figure 1), pheromone traps were deployed from 2016-2018. These included
19 localities in 2016, though due to factors mentioned above, in 2017
and 2018, only 18 and 17 of these localities were sampled, respectively.
Along this transect, moths were collected weekly from late November
through early January. A list of trap locations is provided in
Supplemental Table S1. Upon collection, moths were removed from traps,
placed in glassine envelopes (Uline Inc., Pleasant Prairie, WI), and
stored at -80°C. The total number of moths collected over the flight
period in each trap was counted to provide an estimate of relative
population density surrounding each trap location.