Why Is My Tree Sticky? | Aphid Invasion of 2023

Does any of this sound familiar to you?

I have a question for you. I have a magnolia tree in my front yard and I have sap all over my front porch and roof. It has never done that before. Thoughts?

--Molly H., Regency

My Red Oak tree is dripping a lot of sap (tiny droplets). I know this is not a normal thing for a Red Oak. Could you come look at it and make a professional diagnosis of how this should best be treated?

--Bill L., 120th & Blondo

Have you noticed an unusual, sticky sap raining down on your car or patio this year? Or perhaps sticky leaves that look like they are growing black mold? It could be related to aphids and recent drought-like conditions.

Aphids are harmless, sap-sucking insects that live on many trees in Nebraska. The sticky substance, called honeydew, is excrement from the feeding process. Normal Midwest rain patterns typically wash away the honeydew and the aphids. The recent drought has allowed the Aphid population to explode and resulted in a buildup of aphid by-products, which is why this is now on your radar.

The “black mold” that often co-occurs with aphids is a superficial affliction known as sooty mold. The sticky honeydew produced by aphids allows mold spore strands to stick to leaves as they blow in the wind. The high sugar content promotes further mold production. While high concentrations of sooty mold CAN block out sunlight and inhibit photosynthesis on afflicted leaves, it is rarely detrimental to your tree. Sooty mold is generally just a cosmetic nuisance. Still, if it bothers you, the first step is to control the aphid population.

HOW TO TREAT APHID INFESTATION

Many homeowners have asked if they should treat Aphids with insecticide. While you can use a horticultural oil to treat aphids (and loosen sooty mold), there is generally no need to resort to chemicals. Here we take a note from nature. If your tree is small enough, you can use a garden hose to soak leaves in the canopy. By mimicking standard rainfall patterns, you can wash away the sticky honeydew and drown out the existing Aphids, resulting in population control. BONUS: Your tree will love the water during these hot months!

If your tree is too large to reach with a garden hose effectively, there is an alternative natural treatment option. You can release beneficial bugs that feed on Aphids. The number one biocontrol species for aphids happens to be the beloved Ladybug! 🐞 Studies show that a single beetle can take out 20-30 aphids daily. BONUS: Lady beetles also target weevils, another common garden pest!

Another valid option is to 🥁 …. Do nothing! That’s right. You can also simply choose to wait it out. Aphids are harmless to your tree, so if you can live with the by-products and let nature do what it does best, it will naturally sort itself out.