Keep watch for insects that attack trees

There are a number of pests that harm trees, including yellow-headed spruce sawfly, spider mites, and white pine weevils

White pine weevils target the leader, or top branch, of young spruce trees.
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There are several insects that affect trees that you should keep an eye out for this year.

“The yellow-headed spruce sawfly has been a problem for spruce the last few years, as well as spider mites,” said provincial agro-forestry specialist Toso Bozic. “White pine weevils have also been a problem for young spruce trees, as they target the leader, or the top branch. Poplar and willow tree borers have been very dominant, along with a large infestation of forest tent caterpillars in the northern part of the province.”

There are treatments for some pests, but not all.

“Sawfly larvae can be removed by hand and squished, whereas mites can be controlled with high-pressure soapy water, or by encouraging beneficial insects such as lady beetles. Young willow trees infected by willow borer can be cut to the base of the tree. Unfortunately, there is very little that can be done with large aspen trees infected by poplar borer.”

Besides insects and diseases, other factors can potentially contribute to declining or dying trees, including improper use of chemicals, salt along roads, soil type, wildlife damage, competition, and heavy grazing. Bozic recommends only using insecticides as a last-ditch measure.

“Monitoring is key when it comes to insects. From mid-May until October 1, landowners should check their trees weekly to see what is going on. Monitoring also helps them keep on top of which trees may need watering under dry conditions, or may need help with other issues.”

If monitoring turns up insects, disease, or any other issues contributing to tree weakening, Bozic suggests taking a picture.

“Email a photo to me at [email protected] so we can discuss what you’ve found. If you can also provide photos from the surrounding area it will help me determine the extent of the problem, as well as if other issues are at hand.”

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