 Joe Rimelspach reported that sugar maples in central Ohio are beginning to experience the annual leaf drop caused by MAPLE PETIOLE BORER (Caulocampus acericaulis). Although sugar maples are generally preferred, this sawfly will also occasionally infest other maples. Fortunately, while the number of fallen leaves beneath an infested tree may look dramatic, defoliation seldom exceeds levels that are considered detrimental to the overall health of the tree. This non-native sawfly was introduced into the United States from Europe. It spends the winter in the pupal stage buried 2-3" in the soil beneath the affected tree. Adults emerge in the spring. After mating, the females use their saw-like ovipositors to insert a single egg into the petiole near the leaf blade. The resulting grub-like larva feeds by boring down the center of the petiole. Larvae drop to the ground once they complete their development. They crawl into the soil to pupate and remain buried until the following spring. There is one generation per year. The initial symptoms of a maple petiole borer infestation are highly variable. Some leaves may become wilted and discolored while still attached to the tree, with the petioles collapsing and turning brown just prior to leaf drop. Other infested leaves show no outward symptoms and appear perfectly healthy when they drop from the tree. However, all of the fallen leaves will retain only a very small portion of the hollowed-out petiole. Most of the petiole, along with the larva, remains attached to the tree. Thus, raking and destroying fallen leaves will not reduce the sawfly population. The sawfly has a minimal impact on tree health, so controls are not necessary. For more information, see:
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Last Updated ( Thursday, 08 May 2008 19:14 )
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