The phenological window for western spruce budworm Vince

The phenological window for western spruce budworm Vince Nealis & Jacques Régnière Canadian Forest Service Pacific Forestry Centre, Victoria & Laurentian Forestry Centre, Québec Choristoneura occidentalis Thanks to Meghan Noseworthy, Rod Turnquist, and Vince Waring

Major conifer-feeding Choristoneura budworms in northern forests C. orae Coastal budworm C. biennis Two-year cycle spruce budworm C. pinus Jack pine budworm C. occidentalis Western spruce budworm C. fumiferana Spruce budworm

Late summer winter Life Cycle summer spring early summer

It’s spring! Open the window!

“Budworms are early so they won’t be late” -Bill Mattson Douglas-fir: Bud suitability Strategy 1: Synchronize with bud flush Strategy 2: Take risks early to avoid risk later

Risk of dispersal: the cost to early-birds V. Nealis and J. Régnière. 2009. Agric. For. Entomol. 11, 213 -223

Experimental Design Cohorts of final-instar budworms caged on foliage at several locations throughout season Recovered (or not) as pupae = rate of survival (S) Weight of pupae ~ proxy measure of fecundity (F) Fitness = Survival * Fecundity

Pupal weight is correlated to survival and provides a good prediction of fecundity

Fitness correlates for w. SBW cohorts Coastal BC

Fitness correlates for w. SBW cohorts Interior BC, elevational gradient

Survival of experimental cohorts of western spruce budworm at 4 locations in coastal and the interior of BC.

Conclusions • Seasonally related host-plant condition has a profound effect on budworm fitness. • Budworm is in an annual race against a deteriorating host-plant in all locations. • For period of time examined here, budworms are mostly getting it right. • This race may be run at a different rate depending on defoliation history. • Is this why they come out early; the cost of being late is even greater?

Late summer winter Process-based phenological model summer spring early summer

Western spruce budworm outbreaks are patterned in several ways suggesting weather-related influence. Don Heppner

Major conifer-feeding Choristoneura budworms in northern forests C. orae Coastal budworm C. biennis Two-year cycle spruce budworm C. pinus Jack pine budworm C. occidentalis Western spruce budworm C. fumiferana Spruce budworm