Host Tree Species Affects Spruce Budworm Winter Survival.

Area of Science:

• Forestry
• Entomology
• Ecology

Background:

• Global warming trends suggest potential northward expansion of spruce budworm (SBW) outbreaks into boreal forests.
• Northward expansion is constrained by host tree availability and insect overwinter survival.
• Understanding host-tree interactions is crucial for predicting SBW population dynamics.

Purpose of the Study:

• To investigate the impact of larval feeding on different host trees (balsam fir, white spruce, black spruce) on SBW life history traits.
• To assess the effects on both parental and progeny generations, including overwintering survival and larval weight.

Main Methods:

• Larval feeding trials using balsam fir, white spruce, and black spruce.
• Measurement of key life history traits: pupal weight, overwintering larval weight, and overwintering survival rates.
• Comparison of traits across different host tree treatments for parental and progeny generations.

Main Results:

• Host tree species significantly influenced SBW progeny weight and winter survival.
• White spruce supported the most robust growth (heaviest pupae and overwintering larvae).
• Black spruce was least suitable, yielding smallest larvae and significantly higher winter mortality.

Conclusions:

• SBW's potential northward expansion into black spruce-dominated forests may be limited by reduced offspring winter survival.
• Observed lower survival on black spruce could prevent large-scale outbreaks, even with warming temperatures.
• Host suitability remains a critical factor in predicting insect pest dynamics under climate change scenarios.