Low budworm counts allow more time to prepare

Defoliation samples sites. Stars indicate sites where defoliation consistent with spruce budworm feeding behavior was detected.

In mid-October we presented information regarding the on-going spruce budworm surveys in Maine and in the surrounding provinces.  Notably, among the 3,700 acres of light and scattered defoliation mapped in New Brunswick were several sites in the St. John River Valley between Edmundston and Connors (Madawaska and St. Francis in Maine) and defoliation had expanded and intensified in 2017 in the Bas-St-Laurent region of Quebec and other parts of the Gaspe. Two months later, the Maine Forest Service (MFS) has completed a defoliation survey in sites across the northern boundary of the state, counted some of the budworm tracker’s citizen scientist site samples (all those that have been mailed in), tabulated light trap samples, collected L2 samples (second instar larvae) for the Cooperative Forestry Research Unit (CFRU)-led study, and we are chugging through samples from the network of cooperator pheromone traps.  A summary of the results of those efforts follows. 

Defoliation Survey

This year we quantified defoliation on a subset of MFS-sampled L2 sites and additional sites in northern Maine. The Fettes Method was used to quantify defoliation on current-year growth. This method provides a systematic approach to measuring defoliation.  It was employed during the last budworm outbreak in Maine, and is currently in use in Quebec. MFS staff received training on implementing the method in a July 2016 field training held in the Matapedia Valley in Quebec.  The Fettes method captures defoliation from all causes and can be used to estimate both current-year defoliation and cumulative defoliation.  Here’s a brief introduction to the approach.

Budworm Tracker sample sites: Volunteers agreed to collect samples at these sites weekly or more frequently.

Trace defoliation was recorded at all 26 sample sites, with levels ranging from 0.2 to 3.9 percent foliage missing. Only four sample sites had defoliation that was in a pattern typical for the feeding behavior of spruce budworm. These were found in two sites near Estcourt Station, one site in Cross Lake Twp. and one site in Connor Twp. 

Budworm Tracker

Preliminary counts have been made on samples from sites where citizen volunteers deployed a pheromone trap and made collections on a more or less weekly basis. (Details of the program can be found at www.budwormtracker.ca.) Samples or data sheets were delivered to the MFS office in Old Town from 24 locations. Sites were established from Lubec and Bangor north. 

Catches ranged from 0 to 52 moths, with the highest captures in the north and east.  More information on this project will become available from the Budworm Tracker program next year. This is the second year Maine has been a full partner in this program.

Light Trap Surveys

Another set of sub-season samples comes from the network of people who tend a light trap during the summer months.  Volunteers at these sites collect trap contents daily and regularly mail them in to the MFS lab in Augusta for processing. 

Light trap sites in 2017. Numbers indicate budworm moths captured. Open circle marks former Allagash site.

The light trap network sites captured fewer spruce budworm moths this year than last.  It is apparent from atmospheric transport models and Canadian weather data that the bulk of spruce budworm moth flights from Quebec did not impact Maine, and this may be reflected in the light trap catches. 

Additional impact could be a result of the loss of a key site in Allagash.  This location had recovered spruce budworm in four of the previous five years of operation. 

We would like to find a trap operator to help fill the gap in the Allagash region.  This year, light traps in Calais, Crystal, St. Pamphile and Topsfield recovered spruce budworm.  A total of 41 spruce budworm moths were captured, down from the 2016 catch of 146, but on par with catches in 2014 and 2015. 

L2 Samples

CFRU cooperators including the MFS have been collecting and supporting processing of L2 samples for the last several years. This year samples were requested from a total of 220 sites.  Samples are being processed at cost at the Canadian Forest Service L2 lab in Fredericton New Brunswick.  Final delivery of samples for the year is planned for December 20.  As mentioned previously, defoliation was evaluated on a subset of the MFS sites. MFS plans to continue to collect this measure, at least from northern Maine sites. 

Pheromone Trap Sites

We believe that all the cooperator pheromone trap samples that will come in have been delivered to the MFS office in Old Town (we’re happy to continue receiving them if that belief is in error).  We’re working through the last of those samples and expect to have counts completed by the end of the year or early 2018. To date, approximately 360 samples have been processed and data entered.  Sixty three samples remain. 

The pattern remains the same as reported previously, with highest captures within about 40 miles of the northern border.  Captures also tend to drop off from east to west.  To date, the highest recorded catch is 68.3 moths/trap in T19 R12 WELS. 

Outlook and Future Plans

L2 and trap recoveries should be finalized and a full report of 2017 spruce budworm activities should be available early next year.  We plan to follow up on the fall defoliation survey with a similar survey of sites in northern Maine in early July 2018.  The continued low populations gives forest land owners and managers, as well as others who will be impacted, additional time to prepare for the next spruce budworm epidemic.  More information on spruce budworm can be found at www.sprucebudwormmaine.org.