Maple trees are weeping sap

Asked July 28, 2016, 10:52 PM EDT

My maple trees are weeping sap all summer long, this started last year and is much worse this summer. I have a 20 acre woods and most of the trees are maple. What is the cause of this and can I expect this to continue every summer, it sure makes a mess on everything.

Antrim County Michigan

1 Response

The sticky sap is honeydew excreted by scale insects. If you look at twigs and branches you will see 'bumps'. Depending on which of the several scale insects it is, the bumps will range from tan, brown to fuzzy white.

When honeydew becomes a nuisance around homes, spraying trees at the correct time that overhang decks and driveways can be done by professionals. Homeowners can treat smaller trees with a systemic insecticide at the appropriate time. Treating at the wrong time will not control these insects.

The correct time is determined by which insect you have. Pictures of the insect on twigs of the tree that is overhanging the area can be attached to this question and I will try and ID it for you. Or you can have a certified arborist out to diagnose and treat.
Or you can send twig samples that have insects attached to MSU's pestid lab.
Find certified arborists here---
MSU Pestid lab---

If you can tolerate the honeydew, that is usually the best choice. Insecticides applied too often and too widely destroy good predatory insects that help control these scale insects. So, if necessary, just treat trees that are near the areas you use. Trees in your wooded area will be able to withstand these insects.

All insects have cycles of higher populations and then reduced populations, determined by environmental factors, predators, and our use of chemicals. So scale insects are always present- some years populations will be heavier and some less so. In communities that regularly and widely apply insect sprays scale can be an annual problem because predator insects have been killed.

Here are some links to info on some of the most common scale insects that affect maples and other trees.

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