HOST RESISTANCE TO THE FIR ENGRAVER BEETLE, SCOLYTUS VENTRALIS (COLEOPTERA: SCOLYTIDAE): 4. EFFECT OF DEFOLIATION ON WOUND MONOTERPENE AND INNER BARK CARBOHYDRATE CONCENTRATIONS

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Abstract
Monoterpene production, inner bark carbohydrate concentrations, and fir engraver attacks on grand fir were monitored for 3 years following Douglas-fir tussock moth defoliation. Monoterpenes were reduced for 2 years following defoliation. Defoliation caused a reduction in total sugars the first year following defoliation and a reduction in starch the second year. Total sugars and the previous year’s starch concentrations were positively correlated with monoterpene production. The trees which produced the least amounts of monoterpenes were the ones successfully attacked by the fir engraver.