Roots, Shoots, Fruits & Flowers: Carpenter Ants, Sooty Mold, Crab Apple Tree, & Tuber ID


A black carpenter ant.
Photo: US Forest Service.

Carpenter Ants

Philip has a tree pest and sends this email, “I have an oak tree that is infested with black carpenter ants and there are rings of holes all over the trunk as far up as I can see. How would I get rid of the ants?”

An online search of AgCenter website provided some answers for Philip:

  • Any water-damaged wood should be removed.
  • Wood treated with borates will repel infestation.
  • Treat with Advance Carpenter Ant Bait™.
  • Nests in trees or old stumps can be treated with Orthene™, Talstar™ or other pyrethroids.
  • These ants do not bite or sting.


Satsuma infested with whiteflies that cause sooty mold.
Photo: Dan Gill, LSU AgCenter, retired.

Sooty Mold

Dr. Raj Singh, the AgCenter’s “Plant Doctor”, recently shared a new publication entitled, Sooty Molds, and he writes, “Sooty molds are [harmless] fungi that grow superficially as a thin black layer on leaves, fruit, twigs and stems of various crop plants or trees. The fungi grow on the honeydew produced by insects with piercing-sucking mouthparts. The insects, including aphids, leafhoppers, mealy bugs, psyllids, scale insects and whiteflies, pierce the plant tissue with their stylets and feed on plant sap. While continuously feeding, these insects ingest a large volume of sap fluid into their bodies, and the sap fluid is not entirely digested. After extracting nutrients from the sap, these insects excrete excess water and sugars from their bodies in the form of a sticky, sugary substance called “honeydew.” Most of the time, these insects feed on young, tender new plant growth, and the honeydew drops below on all plant parts previously mentioned. Additionally, the honeydew covers understory vegetation, concrete surfaces, sidewalks, furniture, parking lots, etc., under host plants infested by sap sucking insects.

“Managing sooty molds is very simple. Keep insects, such as aphids, mealy bugs, scale insects and whiteflies, in check. Once the insect problem is solved there will be no new sooty mold occurrence. The existing sooty mold infestation dries out after some time and easily sloughs off the infested areas. Pressurized water can be used to wash off the sooty molds. Care should be taken while using pressurized water because it may damage the plant.

Insect infestations are generally controlled with insecticides, insecticidal soaps, or horticultural oils. Before applying any kind of chemical pesticide, it is very important to identify the insect properly.”


A range map of southern crab apple in Louisiana.
Image: Glen Arboretum.


The bloom of the southern crab apple.

Crab Apple Tree

Dean asked a timely question because we are in the best time to plant trees and shrubs. Winter is a good time to plant because these woody plants are dormant and have less transplant shock then during a planting in early spring. Dean asked, “I am looking to plant crab apple trees. Can you inform me what variety that is native or would do best in our area, Leesville? I am looking to plant it for wildlife.”

The Glen Arboretum of Towson, MD has a range map of southern crab apple (SCA), and the image in this article shows the parishes with known populations in Louisiana in light green. Leesville and Vernon Parish have native SCA trees so SCA would perform well in Dean’s area.

The website of LSU’s School of Natural Resources has a list of wildlife species benefitting from SCA: deer, fox, raccoons, squirrels, & turkey. These animals feed on the fruit. SCA also serves people by providing fruit for jelly and wood for tool handles.


Tubers or storage roots of sawbriar.
Photo: Jennifer Newberry, Natchitoches, LA.

Tuber ID

Jennifer, avid gardener, shared an email and a clear image, “I have a quick question. I was digging in the ground and dug these [things] up. I’m not sure what type of root this is. I would be tremendously grateful [for]any help [you can provide].

Jennifer has sawbriar, or green briar, or cat briar, or smilax. This weed is difficult to remove. Mark Czarnota, Associate Professor of Weed Science at the University of Georgia, made these recommendations for control, “Once the Greenbrier develops an extensive underground rhizome tuber system, it is difficult to control. If it is just one plant, physically removing the plant and as much of its tuber / rhizome system as possible is your best option. If physical removal of the plant is unrealistic or not possible, you should consider the use of herbicides. Herbicides with the active ingredient glyphosate (e.g., Roundup® and others) are your best options.”

“Before you buy or use an insecticide product, first read the label, and strictly follow label recommendations. Mention of trade names or commercial products in this article is for informational purposes only and does not constitute endorsement by Louisiana State University AgCenter.”

“This work has been supported, in part, by the USDA National Institute of Food and Agriculture, Renewable Resources Extension Act Award, Accession Number 1011417.”

2/7/2022 3:34:44 PM
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