As if the summer hasn’t given us enough to worry about in our landscapes with heat, drought, humidity, rain, fungus, and weeds, now sucking insects. The white flies are out in force, and they can be brutal for plants.

A group of veterans and I were shaking our heads the damage at the at the Charlie Norwood Veterans Administration atrium gardenThey were beating up on some Echinacea we planted a few years ago. My friend Phyliss stopped me yesterday and said her yard was loaded up with white flies, as well.

White flies are a terrible pest in traditional agriculture and horticulture when they infest. In the landscape, it is sometimes the byproduct of the insects that is the best indicator of the infestation more than the critter itself. Right now, if you are seeing black on the leaves of plants, it is sure sign that there is a sucking insect infestation. 

What is the black stuff? It is called sooty mold, which is actually a fungus but it is caused by an insect. 

Our most common sucking insects are soft scale, whiteflies, mealybugs and aphids use their needle like mouth parts to drill into the vascular tissue of a plant and drink the plant’s interior juices. The insect excretes a sugary substance called honeydew that collects on leaves and branches. The black fungus is a mess.

Trees and shrubs (as well as cars, patios, furniture, lawn mowers, roofs, driveways, trampolines, fences, small children) below the infested trees will get this mold all over its leaves. Hackberries are famous for producing sooty mold where a type of aphid attacks them every year. Without fail the residue will coat the entire area under these native trees. Crape myrtles are often infested with aphids and will blacken all that resides underneath. Gardenias are notorious for sooty mold because white flies love to breed on the on underside of the evergreen leaves and sometimes turn the entire plant into something that looks like ashes.

Controlling sucking insects isn’t too tough but does require some effort. I like to recommend horticulture oils and insecticidal soaps. On a side note, I don’t recommend homemade versions of these products because if they are formulated too “hot”, you can risk potential damage to your precious plantings. Commercially made horticulture oil and insecticidal soaps are mostly inexpensive and are known to work. These products work by covering the sucking insects and suffocate them.

Occasionally in plants like gardenias where white flies lay their eggs, the infestation is on the underside of the leaves which means you have to do some fancy maneuvering to get the treatment to cover the hidden pests. Sometimes plants like magnolias will have scale and about the maximum you can reach with a sprayer is about 30 feet unless you have some commercial equipment, so precision spraying isn’t really an option.

Be super careful and don’t apply when it is above 90 degrees because these oils and soaps can damage the targeted plant.

For large plants like hackberries that are beyond the reach of a sprayer, systemic insecticides like imidacloprid and dinotefuran can be used to treat for sucking insects. The chemicals are added to water and then the soil is drenched into the feeder root area of the plants.

The insecticide will absorb into the plant and move through the vascular system throughout. The insect will then bite into the plant and chemical inside will poison the insect and the and the pest will croak.

Try and avoid the systemic insecticide approach altogether if possible and especially if the plant is going to bloom within 4-5 months of application because these type chemicals can hurt our pollinators.

Sooty mold usually will not cause long-term damage except when the plant is covered for extended periods. When the leaves are covered for a long time, there is a restriction in sunlight penetration that keeps the plants from photosynthesizing properly. After treatment and the insect is dead, the sooty mold will eventually flake away.

Heavy, untreated infestations can lead to long term damage, so be diligent and keep an eye out. Your plants will appreciate it. If you catch it early, you won’t have to spend a precious Saturday afternoon with a pressure washer.