Dealing with any pest problem can feel daunting, especially if you have a large tree. It can be hard to spot tons of tiny critters spread across all those branches–let alone keep them under control!
But if you’re like Davey blog reader Joan from Illinois, you want to get to the bottom of it. Joan spotted tiny bugs living on her maple’s leaves, so she reached out for treatment tips.
From what Joan shared, it sounded like aphids! Here’s how to tell if that’s the case for you, too, and what to do about it.
How to Get Rid of Aphids and Their Sticky “Sap”
Why am I finding sticky leaves on outdoor plants or dripping sap from my maple tree leaves?
That sticky film covering your plant’s leaves? It’s called honeydew—but it’s not so sweet.
Honeydew is the waste aphids and several other sap-sucking insects leave behind after snacking on sap. Along with tree leaves, it can drip onto branches, patios, driveways or any areas under the canopy. It can overtake your outdoor space, creating a massive, sticky mess every direction you look!
Plus, a plant stressed by feeding might develop yellow or curled leaves. Though, the leaves or other surfaces may turn black if the honeydew attracts sooty mold fungi.
Though the symptoms sound ugly, aphids actually don’t do much damage to healthy, mature trees. But, if you want to do away with the creepy critters, or save your property from sticky honeydew, here’s what to do.
How to Get Rid of Aphids on Large Trees (Including Maples)
Believe it or not, one effective way to control them is to do nothing at all! Several natural enemies like ladybugs and parasitic wasps prey on these pests. And it only takes a few predators per plant to significantly cut down on the number of bugs.
If you want to take the job into your own hands, hose your tree down. A strong gust of water knocks aphids right off, and once they fall, it’s not likely they’ll find their way back.
If those don't work for you, bring in the horticultural oil, which smothers and kills the insects on contact.
“Horticultural oil is extremely effective in controlling aphids, but only if you thoroughly treat the tree,” said Lou Meyer of Davey’s Annapolis, Maryland, office. “Apply the oil in the dormant season to kill any overwintering eggs. If needed, you can also use a lower rate of the oil during the growing season as well.”
Or there are insecticides that can be applied to the soil to treat for aphids if spraying isn’t viable.