AG NEWS CARY SIMS: Honeydew in the Landscape
This is not the honeydew melon with the sweet green flesh and not the honey-do list you have at home. The honeydew that I’m getting calls about is the excrement of aphids and other plant sucking insects in your landscape. As one author stated, “It consists of the unusable byproducts of the digestion of sap.” Let’s just call it aphid poop.
We notice it coating the tops of leaves in your landscape and, if you park under branches of trees, the sticky substance on your windshield as well as top of your vehicle. Scale and aphids tend to be the biggest culprits as they excrement a sugar-laden pass-thru as a result of their piercing/ sucking feeding habits.
On large oak or other deciduous trees, the presence of aphids or scale is not a concern. These trees have been thru much worse over the years and will survive their feeding just fine. Established shrubs can also experience their presence without too much of a fuss. Often, on smaller shrubs, homeowners will first notice a black mold growing on the leaves. This is called Sooty mold and is growing on the honeydew.
Sooty mold makes a sticky, black layer on leaves that have been coated in honeydew. Look around your landscape and you may find this same sticky, black material on lawn furniture, sidewalks, your vehicle, or anything directly under the vegetative canopy of an aphid or scale infested tree.
Sooty mold can be cleaned up with a soapy mixture in your sprayer. While this will not stop the cause, it will clean it up.
Crape myrtles are especially prone to having sooty mold from aphids. In recent years, a very serious pest, the crape myrtle bark scale has taken sooty mold to a whole new level, and has been causing loss to these beloved shrubs in the landscape. You can easily identify crape myrtle bark scale against the common aphid if you find the sooty mold growing on the stems in addition to the leaves.
The scale adult females can be identified as a “felt-like” white or gray coating that covers woody tissue from small twigs to large trunks. Crush them and you’ll see a pink “blood”-like liquid. Uniquely, crape myrtles really didn’t have a scale insect to worry about, so finding any scale on this small tree should be highly suspicious.
If you want to prevent honeydew from landscape trees and shrubs, treat against aphid and scale insects. Use a systemic insecticide with the active ingredient Imidacloprid. Apply the systemic product as a drench in late spring. Throughout the winter, use a horticultural oil as a good pesticide for scale by applying liberally to the stems during winter months.
Those aphids and scale that make it past these two measures can be eaten effectively by the some lady beetle species, specifically the Twice-stabbed lady beetle.
Cary Sims is the County Extension Agent for agriculture and natural resources for Angelina County. His email address is firstname.lastname@example.org
Educational programs of the Texas A&M AgriLife Extension Service are open to all people without regard to race, color, sex, disability, religion, age, national origin, genetic information or veteran status. The Texas A&M University System, U.S. Department of Agriculture, and the County Commissioners Courts of Texas Cooperating.