Maple tree weeping sap liked rain

Asked September 18, 2020, 10:44 AM EDT

I'm worried about the sticky droplets coming from my maple tree. It looks like rain drops on my car and feel sticky to the touch.

New Castle County Delaware

1 Response

If a sticky substance is "raining" from your maple tree, it is not sap but honeydew from aphids which are feeding on your tree. If you see ants crawling up the tree, they are farming the aphids and protecting them from their natural enemies. So the first thing to do is to stop the ants. You can do this with a sticky tape, such as Tanglefoot, around the trunk or use baited ant traps on the ground around the tree. Once the ants are not present, the aphid predators can usually control the aphid population.

If the infestation is too great, you can use a systemic pesticide containing imidacloprid. You put this into the ground and water it in. The tree roots will absorb it and transfer it to the leaves where the aphids are feeding. This is a reasonable time of year for this treatment as it will also kill pollinators if the tree is blooming so it's not a good idea to use it in the spring.

Aphids will not usually kill a tree but their honeydew often brings a sooty fungus which is unsightly and can kill the tree by blocking out sunlight from the leaves.