What Is the Sticky Mess in Pecan Trees?

Have you parked your car under a pecan tree lately?  You might get a fresh coating of honeydew!  In fact, just about anything that walks under a pecan tree or sits near a pecan tree might be covered in this sticky coating.

The real culprits behind the honeydew are aphids.  Aphids are soft-bodied insects that suck sap from plant leaves.  Many species of aphids exist and attack various plants, but two types of aphids attack pecan trees and secrete honeydew, the yellow pecan aphid and the black-margined aphid.

Both species of aphids lay eggs that overwinter on twigs and tree trunks.  The nymphs, or immature aphids, hatch in the spring and feed on new leaves.  The nymphs mature in about a week and can give birth to live young.  The females can reproduce without males in the spring and summer.  In September and October, male and female aphids develop and mate.  The females deposit eggs that will survive the winter and begin the process again.  Needless to say, aphids can reproduce quickly!

These aphids have mouthparts that pierce leaves and suck water and nutrients from plant leaves.  After feeding, aphids excrete excess sugars, also called honeydew.  Honeydew can fall to the ground, which is what we are seeing on our cars and sidewalks.  It also collects on leaves and is a food source for black sooty mold that can grow on leaves.

Yellow pecan aphids increase in number late in the season.  An outbreak of this species can cause defoliation and a reduction of pecan yield and quality.  Treatments for yellow pecan aphids is not usually advisable for homeowners because insecticides can also destroy their natural enemies, causing a surge in aphid populations.  Wind, rain, and natural enemies will often cause a decline in yellow aphid numbers.

Black-margined pecan aphids typically increase in number in June through August, but they usually decline without causing much damage.

Honeydew can be an annoying problem, especially when it covers your car!  My grandma has some wise words that apply to this problem of pecan aphids and their sticky mess, “This too shall pass.”

For more lawn and garden information, contact Kate Whitney, Williamson County Extension Horticulturist, at 512-932-3300.


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