Diapause in Forest Insects: From Eco-Physiological Adaptations to Management Applications

Forest insects worldwide face changing environments within a given year and across multiple years. Therefore, insects must match their life cycles with critical resources to maximize fitness and survival. A key strategy for life-cycle synchronization is entry into a special form of dormancy, called diapause. Diapause affects multiple life-history traits, including development, reproduction, movement, stress resistance, and energy storage. This review provides an overview and discussion of diapause expression for forest insects, focusing on ecologically and economically relevant plant-feeding species and highlighting specific, diapause-related features of forests. Diapause regulation and expression are highly variable across species and mainly help overcome unfavorable periods, synchronize life cycles with host trees and predators, and respond to scarce or irregular resources. Changing climatic conditions have direct and indirect effects on forest insect diapause, including temperature stress, energetic stress, and phenological mismatches. Knowledge of diapause regulation is essential for practical forestry to coordinate and evaluate management measures.