Use of an Insecticide in Field-Scale Plant—Herbivore Studies: No Side Effects of Synthetic Pyrethrin onBetula pendulaGrowth or Chemistry

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Birches are ecologically and economically important trees in forest ecosystems and commonly used in studies of plant—herbivore interactions. Such studies often require manipulation of natural levels of herbivory. In field conditions, this can be executed using insecticides, but such experiments have to assume that the insecticide has no side effects on the study plant. Here we (1) provide results of a test of the effects of synthetic Pyrethrin, deltamethrin, on growth, leaf and litter chemistry and litter decomposition rate of Betula pendula seedlings in controlled growth chamber conditions, and (2) illustrate effectiveness of the insecticide in a field study of the effects of insect herbivory on B. pendula. The field effects, a significant reduction in leaf damage and a corresponding increase in growth, show that we used an effective dose of deltamethrin, while the results of the growth chamber experiment show that the dose did not cause any side effects on B. pendula seedling growth or chemistry. We conclude that Pyrethrin compounds can be safely used for reducing insect-herbivore load on B. pendula in field-scale studies of tree—herbivore interactions.