Effect of Plant Growth Regulator Paclobutrazol and Fertilization on Paper Birch and Austrian Pine Resistance to Folivores
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Date
2006-04-18T01:37:48Z
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Abstract
Plant defense theory predicts that environmental factors that limit growth of plants more than their rate of photosynthesis should increase secondary metabolism and insect resistance. Applications of the plant growth regulator paclobutrazol slowed the growth of paper birch and Austrian pine with no effect on photosynthesis. In response, foliar concentrations of condensed tannins in birch increased as predicted, but with little effect on insect resistance. Growth and survival of gypsy moth, and forest tent caterpillar were not affected over the three year study period, and growth of whitemarked tussock moth larvae was reduced only slightly in one year. Contrary to the predictions, pine monoterpene concentrations were not affected by paclobutrazol and increased in response to fertilization. Nevertheless none of the treatments affected pine resistance to the European pine sawfly. Fertilization had no effects on tree growth, possibly due to high background levels of soil fertility, and decreased birch resistance to gypsy moth during the second year of study, but otherwise had no effect on insect performance. Although paclobutrazol decreased tree growth as expected, results provide little evidence to support claims that it can be used as a tool to enhance insect resistance.
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paclobutrazol, plant defenses, insects