Variation in host foliage nutrient concentrations in relation to western spruce budworm herbivory

Abstract

The western spruce budworm, Choristoneuraoccidentalis Freeman, prefers to feed on early season, new foliage; phenological age of host foliage has profound influences on larval growth and development. Budworm growth, survival, and reproduction also differ with host plant species. Seasonal and interspecific variation in foliar nutrients suggests that they may be key nutritional factors affecting budworm performance. Foliar concentrations and balances of N and eight mineral elements (P, K, Ca, Mg, Mn, Cu, Fe, Zn, P/N, Cu/Zn, Mn/Fe, and Ca/Mg) in current-year needles varied with season and tree species (Pseudotsugamenziesii (Mirb.) Franco, Abiesconcolor (Gord. & Glend.), and Piceaengelmannii Parry ex Engelm.). Seasonal trends occurring in all host species as the new needles matured were (i) declines in N, P, K, and Zn; (ii) increases in Ca, Mn, P/N, Mn/Fe, and Ca/Mg; and (iii) an increase followed by a decrease in Fe. Nutrients showing distinct differences among host species included N, P, K, Ca, Fe, and Zn, plus the Cu/Zn ratio. Mg and Cu were different among some but not all host species or sampling times.