Roots, Shoots, Fruits & Flowers: Ambrosia Beetles, Hag Moth Caterpillar, Tiger Moth Caterpillar, and Pink Striped Oak Moth

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A crape myrtle infested with Asian ambrosia beetle. Photo: Violet Redger.

Ambrosia Beetles

The title of the article could have been “Bugs, Bugs, Bugs” because only insects are discussed this week. Most of them are moths, but a harmful beetle starts this column.

Violet, a landscape professional, sent this email and image concerning the crape myrtle of one of her clients, “I have never seen the like, [AHA]! There seems to be a bug or maybe a bore of some kind mining tiny holes in this crepe myrtle. The saw dust looks like roots have sprouted… so very odd! What do you think?”

Dan Gill, retired horticultural specialist, described the symptoms of an infestation of the ambrosia beetle, “As they bore into the trunk, they push the sawdust-like material out behind them. This is what forms the thin columns of sawdust you see sticking out from the trunk. They tend to attack trees that are stressed, low in vigor, have wounds or other preexisting problems.”

Dr. Raj Singh, the AgCenter’s “Plant Doctor” responded to the Violet’s email, “Yes, it is ambrosia beetle. Soil drench with Bayer Advanced Systemic ™ insecticide for tree and shrubs.” A soil drench would be poured on the ground near the tree trunk to enable the tree roots to take up the insecticide. Spray treatments are ineffective for boring insects like the ambrosia beetle.

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A hag moth caterpillar. Image: James Burnett, Jr., LA Master Gardener.

Hag Moth Caterpillar

Readers of RSFF tend to be precise in their questions. James also asks a brief question, “What is it?”, and he included this image with his question.

Virginia Cooperative Extension has information about the hag moth caterpillar, “The bizarre appearance of the hag moth caterpillar makes it easy to recognize. They have nine pairs of fleshy appendages on their sides, some of which are long and twisted. These appendages look somewhat like legs but are not used for movement; the caterpillar’s real legs are found under the body. The caterpillar is densely covered with short, brown hair. Some of these hairs are hollow and connect to toxin glands in the skin. Contact with these spines produces a burning, itching sensation along with redness and inflammation like a bee sting.” The “take home” message for this insect is to that it is one of the stinging caterpillars so avoidance will prevent a painful contact.

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The caterpillar of a tiger moth. Photo: Stacey Schlittenhard.

Tiger Moth Caterpillar

Stacey complained about caterpillars on her marigolds, “My marigold leaves were massacred by a ton of caterpillars. Do you have any idea of what kind of caterpillar these are? They have been dealt with harshly on my part. I [used Bug-B-Gone ™ on] them. It took them about a day to eat 75% of my marigold leaves.”

An insect specialist from the AgCenter made this identification, “I don’t recognize this one for sure. This image looks to be one that is either getting ready to pupate or is dying. But my best guess is one of the [caterpillars for a tiger moth].

Because this pest is a moth, it would be a candidate for an organic treatment with Bacillus thuringiensis or Bt. Bt will infect caterpillars and kill them. Products like Dipel™ or Thuricide™ have Bt, and this kind of product are safe for people and pets because they have stomach chemistries based on acidity, and Bt would not survive in that harsh environment.

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A pink striped oak moth. Photo: Harvey Kieffer.

Pink Striped Oak Moth

Harvey also sent a question because he was concerned about his trees, “I have three of these [moths] flying around on my from porch. Should I be worried?”

AHA asked Mr. Wood Johnson, a forest entomologist with the US Forest Service about this moth, and Johnson shared his thoughts, “The moth is definitely an…oak worm. [It] probably is pink striped [oak moth] but [it] could be [an]orange striped [oak moth] ([I am] just not certain from photo resolution). Regardless, I agree that the defoliation may slow growth, but trees almost always recover. So long as larvae do not begin feeding on a newly planted or young sapling in his yard, I would not worry about them.”

If you want to contact Roots, Shoots, Fruits and Flowers, please send your questions and pictures to Keith Hawkins, Area Horticulture Agent (AHA), 337-463-7006 or khawkins@agcenter.lsu.edu. Also, you can be on the “green thumbs” email list by emailing your request to the address above.

“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.”

8/13/2020 8:19:07 PM
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