L.K. Hartling, J. Proude, D. Winter, D. O'Shea, D. Lavigne and N. Carter
SERG Project # 2001/05
Hemlock looper (Lambdina fiscellaria fiscellaria (Gn.)) populations did not reach large outbreak levels, hence conclusions from this study pertain to the conditions encountered. However, the study did allow the opportunity to help refine existing methods for forecasting and monitoring, essential cornerstones of good Integrated Pest Management and overall Best Management Practices. Furthermore, this report integrated data from this study and previous DNRE studies, and compared these findings with that of other jurisdictions. Such information will be invaluable if future foliage protection programs become necessary.
The study was able to build on relationships between pheromone trap catch and egg density, egg and early instar larval counts, egg counts and defoliation, and larval numbers and defoliation. Evaluation of pheromone trap survey data showed that pheromone (10-ug strength lure) trap catches of <1200 moths/trap are unlikely to represent threatening populations because associated egg densities never exceeded 15 eggs/100-cm lower-crown branch. Furthermore, counts up to 25 eggs/100-cm lower-crown branch seldom caused >10% loss of current-year foliage, and seldom exceeded 25% loss of the 3 older age classes of needles.
Most of the egg parasitism in not accounted for when sampling in the fall and winter months. Significant increases in egg parasitism were caused by spring-attacking parasitoids. Any population forecast derived solely from sampling in the fall and winter months could underestimate egg parasitism, and thus have the potential to overestimate the forecast. When planning control plans it is probably prudent to include spring egg surveys to see if treatment areas can be excluded.
A trial indicated that pheromone traps might be placed out 1 - 2 weeks earlier than `normal', thus giving some logistic flexibility to surveys at that time. Furthermore, it may be possible to retrieve traps one or two weeks earlier, a significant advantage in areas of higher elevation where snowfall comes early in the season. Data should be collected over several years to strengthen these observations.
Degree-day relationships were further developed to aid in forecasting egg hatch and larval development, both essential to `timing' and assessing control operations.
While not intended as a major component of this project, opportunities arose to evaluate methodology for sampling eggs and larvae, and assessing feeding damage of the current and older age classes of foliage. Likewise, techniques for measuring larval populations (e.g. branch sizes and location within trees), and assessing defoliation of current-year and previous-years' foliage on balsam fir were examined.
Results from this project are expected to be pertinent to various agencies, landowners and other forest management groups dealing with hemlock looper outbreaks in such jurisdictions as Nova Scotia, Québec, Ontario, Newfoundland and the State of Maine.