Roots, Shoots, Fruits and Flowers: Lightning strike, wavy basketgrass, hardwood stump borer, tree wounds, “duck lips” and bleach drift?

“Roots, Shoots, Fruits and Flowers” is a landscape blog that invites homeowners to submit questions about their plant and garden concerns. This edition will look at assorted tree issues.

Close-up of a damaged tree.

Live oak with a lightning scar. Photo by Infrogmation of New Orleans

One of the blog readers sent a picture of a scarred live oak. She wrote, “The tree that you recently looked at for my aunt in Lake Arthur, it was struck by lightning yesterday afternoon. I am attaching pictures of the damage. At this point do they just watch for branch decline? From what I have researched, it seems like it is just a wait and see kind of thing. I welcome your advice on this situation.”

According to the Texas Agrilife Extension website, “If only one side of the tree shows evidence of a lightning strike, the chances of the tree surviving and eventually closing the wound are good. If the tree survives long enough to leaf out the following spring, then the chances of recovery are much greater. Watering and fertilization are suggested to reduce tree stress.” Also, live oaks are tough trees, so the future of this particular tree is promising.

Close-up of basketgrass.

Wavyleaf basketgrass (Oplismenus undulatifolius), a non-native invasive plant. Photo by Steve Fitzgerald

One homeowner brought a weed sample for identification because it was displacing his St. Augustinegrass. An LSU AgCenter weed specialist identified it as wavy basketgrass.

According to the University of Maryland (UM) Extension, “This forest grass from southeast Asia … had spread to cover acres of wooded ground, outcompeting native plants.” This weed is highly shade tolerant, and “the plant blooms in late September and into October, producing small seeds that stick to everything, including passing people and animals who disperse it to new areas.”

Basketgrass seems to mimic cogongrass in the way it will invade a woodland, prevent natural regeneration of trees and displace native plants and animals.

UM Extension offers this treatment, “To control this grass, you can hand-pull small populations, preferably before it goes to seed. If it has already spread to a wide area, you can spray it with 1% to 2% glyphosate. If you accidentally wander into a patch of wavyleaf basketgrass in seed, try to remove all the seed immediately, disposing of the seed in the trash.”

Close-up of a mantidfly.

Mantidfly, a beneficial insect. Photo by Andy Reago and Chrissy McClarren

A retired forester sent a picture of an insect taken with his cell phone. At first, the image looked unreal, like an alien insect from another dimension. It appeared to have a duck’s bill.

In the image, the front legs are folded to look like duck lips from this angle. Victoria Bayless, curator of the Louisiana State Arthropod Museum, identified the insect as a mantidfly. According to Texas A&M Agrilife Extension Service, it is “medically unimportant” which means it is harmless and stingless. They also noted, “Immature stages feed on spider egg masses or larvae of wasps” so it is a beneficial insect.

Close-up of a damaged tree trunk.

Close-up of a damaged tree trunk.

Two different trees with wounds. Photos by Keith Hawkins

Another follower sent an email and a couple of pictures for comment, “I need your assistance identifying what is happening with two trees.”

Both trees have old wounds, and they are callousing over very well. The wood of these trees seems to be solid, and the wounds will be calloused over eventually. The tree on the far left looks like a wound from some type of equipment contact. The tree on the right has a wound from an earlier pruning. Based on these images, these trees should be around for a long time.

Close-up of a hardwood stump borer insect.

Hardwood stump borer (Mallodon dasytomus). Photo by Kiran Lyn and Noah Baker

A professional exterminator wanted to learn about a possible plant pest. He wrote, “I am not as good on my plant pests as I am my structural pests. Someone sent me the attached [image] to identify and said they found it on a fig tree. Any ideas? It looks like a newly emerged beetle of some sort that has not had time for the exoskeleton to harden.

Chris Carlton, an entomology diagnostician at LSU AgCenter, helped with the identification. He said, “Almost certainly [a hardwood stump borer]. If it is still alive, putting it in some moist soil and rearing the adult would confirm. The size, head orientation and antennae are all wrong for the fig borer. I rarely see that species and did not know it was a pest.

An online resource,, provided additional information about this insect. “The larvae of this species are usually found inside tree stumps, decks and other wooden structures. Sometimes it is found in living trees that have not been cut down. They eat away at the wood as they develop. They leave holes in the wood as they exit the tree. It can take three to four years for a grub to fully mature. Most types of hardwood trees can serve as hosts for this type of beetle like willow, maple, oak, elm and pecan trees. In large numbers, hardwood stump borers can negatively impact furniture, flooring and other wood-based industries.”

Our friends at Texas A&M Agrilife Extension advise this precaution, “The [adult form of the] hardwood stump borer is not an aggressive beetle and is not considered dangerous; [however,] the hefty mandibles it has will draw blood if handled carelessly and aggressively.”

Close-up of a hand holding a damaged leaf.

Oak leaf blister (Taphrina caerulescens), a type of fungal disease. Photo by Whitney Mattila

landscape contractor brought in a branch from an oak tree with numerous leaf spots. The uniformity of the spotting looked suspicious. After asking the landscaper about any treatments, he said the homeowner had washed his house with a bleach solution. I suspected a drift problem from the bleach treatment.

However, this diagnosis was wrong, and the condition is a fungal leaf spot and not bleach drift as suspected.

Raj Singh, LSU AgCenter’s plant disease specialist, wrote, “These are in fact fungal leaf spots. It looks uniform in pattern because there are so many of them. But if you look closely, there are a lot of different sizes, and no two leaves have the same pattern. Also, the spots have characteristic fungal characters including light tan centers with dark brown margins. Bleach drift will be more a blight or burn kind of damage leading to loss of chlorophyll.”

OK, these are leaf spots, but what kind? At this point, the best estimate is tubakia leaf spot, a fungal disease. Because it is late in the growing season, the best treatment for this condition is to gather the leaves after they fall off and destroy them to prevent spread of this disease.

5/15/2024 10:40:27 PM
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