By: Jeffrey P. Hagfors, Certified Arborist WI-0181A
Zimmerman pine moth is a very serious insect that affects the health and structure of Austrian, Scots and other pines found in Wisconsin. The life cycle of Zimmerman pine moth is complex. Applications to control this insect are very time specific. Random “shotgun” or “cover sprays” performed by inadequately trained arborists or lawn service technicians will not offer any control for Zimmerman pine moth.
Understanding the life cycle of Zimmerman pine moth is paramount to achieving control.
Beginning in early spring, generally around mid-April, the partially grown larvae that have overwintered on the tree begin their feeding. They start by feeding on the bark. This is the first time to apply the appropriate treatment. If left untreated, they continue to feed and grow. The larvae then move into the trunk and branch wood where they tunnel into the wood, weakening the wood and compromising the structural integrity of portions of the tree. While tunneling in the wood, large globs of sticky resins mixed with sawdust are present on the trunk and branches. These weakened areas of the tree often break during wind storms and heavy snow loads. Damage can be very significant, often necessitating complete tree removal.
The Zimmerman pine moth larva completes its metamorphosis late in summer when it emerges out of the trunk and branch wood as an adult moth. The cycle is ready to repeat itself as the eggs are laid in bark crevices, branch collars and near wounds. These eggs hatch quickly, in a matter of a couple of weeks. The new larvae feed on the bark and begin their preparations to survive the winter. This is the only other time when the insect is small and on the outside of the tree where it can be dealt with using the appropriate application.
Chemical treatments must be properly timed to gain control. We monitor the flowering of indicator plants and the cumulative balance of growing degree days. This lets us know exactly when to begin making these applications. Newly hatched or very young larvae are most vulnerable to treatments. Fully-grown larvae are not susceptible to control, because they are hidden inside the tree. Insecticides must be properly timed in early spring and late in summer. Treatments may need to continue for several years.
Zimmerman pine moth is a common pest in Wisconsin. Controlling it requires much more than guesswork. Trust the Certified Arborists at Wachtel Tree Science and Service to help you retain your pine trees and protect them from this serious pest.
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