Budworm moths caught in traps increase across Maine

By Alison Kanoti, State Entomologist, Maine Forest Service

  • Light traps: In 2019, 17 light traps were operated statewide and we witnessed a dramatic increase in light trap catches, with 502 adult SBW moths caught at twelve sites, although not the same sites as in 2018 
  • Overwintering larvae: Just under six percent of sites were positive in 2018, with a combined total of 25 larvae recovered from 17 of 290 sites. Just over 10 percent of sites were positive in 2019, with a combined total of 70 larvae recovered from 30 of 271 sites.
  • Defoliation Surveys and Assessments: Although no defoliation was detected during aerial survey (feeding needs to be approaching a moderate level of damage before it is visible from the air.) Defoliation assessment indicated there was in fact a shift towards higher levels of defoliation severity, with fewer sites being categorized as trace and more sites now falling into the low and moderate categories.

The recently released report, Spruce Budworm in Maine 2019, details an increase in the number of spruce budworm moths caught in pheromone and light traps across Maine.  This is most likely due to mass migrations from areas with significant defoliation in Quebec. The results included the highest average pheromone trap catches in Maine since trapping began in 1992. (The last epidemic waned around 1985. ) Additionally, surveys for overwintering larvae uncovered a slightly higher proportion of positive sites than previous years.  I am glad to report however, that neither ground nor aerial surveys revealed budworm-caused defoliation. 

The trap numbers remind me of 2013 when mass migrations of fewer moths sparked renewed interest in spruce budworm and the formation of the Spruce Budworm Task Force in Maine. At that time, there was speculation from the Maine Forest Service (MFS) that defoliation would occur within the next five years. The prediction of onset of defoliation was early, but the call to attention was productive. 

A road map was developed by the task force to respond to the pending outbreak.  A professional website was developed with input from the task force communication team and made possible by the University of Maine’s Center for Research on Sustainable Forests.  Forest managers across the state have taken stock of the resource they manage with an eye for potential impacts from budworm.  Many, through adaptive management, have made efforts to reduce timber losses due to budworm impacts.  More than 20 organizations participate in a trap network to monitor populations, and many also participate in sampling for overwintering larvae.  In the MFS, we have made sure that a new generation of our field personnel in northern Maine have seen the signatures of budworm damage so that earlier detection is possible.

I am hopeful that similar thought and action has been given to resources other than timber that will be impacted by a spruce budworm outbreak, or at least that people will not be surprised by the outbreak.    

When will it arrive? I’ve learned a lesson from those that came before me, and I will not hazard a guess.  Budworm populations are on an upward trend in Maine, building towards epidemic numbers. There is little doubt that this generation of trees, and those who depend on them for a living, will feel impacts from this native insect.  This period of relatively low populations of spruce budworm provides continued opportunity for management and planning for its arrival.