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Archive for October 5, 2011

Ribbed Petiole Poplar Gall

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If you look at enough Trembling  Aspen (Populus tremuloides) leaves (and to some degree, those of other poplar species), you are bound to come across some that have an oval swelling about the size of a pea where the leaf  and stem, or petiole, meet.  This swelling is a gall – an abnormal plant growth caused by chemicals coming from the moth (Ectoedemia populella) that laid an egg at this spot this past summer, or from the chewing of the hatched larva as it bored its way into the stem of the leaf.  This gall provides shelter and food for the developing larva, which will, after the leaf falls, go down into the ground to pupate.  An adult moth will emerge next  spring.