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Roots, Shoots, Fruits & Flowers: Armyworms, Woolly Bears, Honeybee Safety and Mud Dauber Wasps.

Keith Hawkins
LSU AgCenter Area Horticulture Agent (AHA)

This week gardeners share their questions and photographs about insects in their gardens and landscapes. Wayne and Ruth have a vegetable garden and wanted to know, “These worms are eating holes in my okra. Would you please tell me what they are and how to get rid of them?”

AHA suspected that this caterpillar is an armyworm. Dr. Sebe Brown, an AgCenter specialist, confirmed, “It’s an armyworm. A spinosad [product like Spinosad Natural Guard Concentrate] will do the trick.” The National Pesticide Information Center shares this information about spinosad, “Spinosad is a natural substance made by a soil bacterium that can be toxic to insects… It is used to control a wide variety of pests. These include thrips, leafminers, spider mites, mosquitoes, ants, fruit flies and others.”

AHA found a yellow caterpillar in his landscape and thought it may be a type of tussock moth.

However, Ms. Victoria Bayless, an insect specialist with LSU, shared this observation, “I think it is a yellow woolly bear, but I’m not sure.  The body is more yellow than our tussock moths usually are.”  The diet of this caterpillar includes many species of grasses, herbs, and trees, but rarely becomes a nuisance in the landscape. The yellow woolly bear becomes the Virginia tiger moth and occurs in in North and Central America.

Peggy uses an organic pesticide with Bt (Bacillus thuringiensis) and wants to know, “Is Bt safe to use around honeybees?”

The short answer to Peggy’s question is “yes”. Dr. Dennis Ring, an AgCenter specialist, wrote in 2019, “[Bt] does not kill predators, parasites or bees.” There are several different Bt strains capable of killing these pests: caterpillars; and mosquito, midge, fungus gnats and blackfly larvae; and May or June beetles (white grubs); and Colorado potato beetle, elm leaf beetle and willow leaf beetle larvae. However, Bt will harm desirable caterpillars of the monarch and other colorful butterflies so use Bt for specific caterpillar pests. 

Some products with Bt include Dipel™, Thuricide™, Monterey Bt Liquid Concentrate™ and many other brands of this organic pesticide. 

John D. came by the AgCenter recently and wanted information on controlling mud dauber wasps (MDW). 

The wasp and hornet sprays sold in garden centers would be suitable for control. However, Dr. Dale Pollet, retired insect specialist, shared a useful note about MDWs, “Mud daubers prey entirely on spiders. Break open a mud nest and observe the array of spiders collected as food for the next generation.” MDWs will prey on black widow spiders, a dangerous, venomous spider. After advising John about this benefit, he decided he would tolerate their nests in his carport. 

Brenda examined the green beans in her garden and sent email asking, “What’s bugging me?”

Again, Ms. Bayless assisted with the identification, “That is the giant leopard moth (woolly bear caterpillar).” This pest would be a candidate for Bt treatments to control the damage to the green beans. 

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.”