​Roots, Shoots, Fruits & Flowers: Walnut Caterpillars, Kousa Dogwood and Two Insects Identified

210_fig_1_trichogramma-wasp---web_1_1200x1200jpgA minute parasitic wasp laying its egg in a tiny, tiny moth egg. Photo: Groworganic.com

Walnut Caterpillars

Over the past few years, Gary, like many people in southwest and central Louisiana, has been struggling with walnut caterpillars (WCs) and the defoliation of pecan and walnut trees. He sent this email to AHA to share a possible control treatment for WC, “After our conversation about the walnut caterpillar the other night, I began thinking about pupa control methods. Then I remembered this company [that] I used to order from and [this company sent] the parasitic wasps...I have successfully used [a beneficial] wasp to control corn ear worm in the past. In the description of controlled pests, it lists several caterpillars that are problems to pecans. This is the method I am going to try this year on our trees.

When using these for corn ear worm control, I had almost no damage in a good size garden planting with only one treatment application of one tab. The eggs tabs almost look like a postage stamp size piece of sandpaper.”

Gary is referring to the “minute parasitic wasp”, and it parasitizes the eggs of moths before the eggs hatches its tiny caterpillars. The company mentioned above sells a “card” for $30 and each card has thirty tabs. A card has about 100,000 wasp eggs. These wasps are very, very tiny and only attack the eggs of moths by laying its wasp eggs in the moth egg and prevents the development of the caterpillars.

While the use of a beneficial wasp is an organic treatment and is effective on corn ear worms and some other caterpillars, there is no evidence that this small wasp will attack WC. Will this method work? Let’s hope so. If you try this method and it works or not, let AHA know.

210_fig_2_kousa_dogwoodjpgBloom of the Kousa, or Japanese, Dogwood.
Photo: The Ohio State University.

Dogwood

Sherry asked this question, “Would Kousa dogwoods suffer the same blight as regular dogwoods in Louisiana? [I] Don't want to buy one if there is a chance it will not last.”

The native flowering dogwood has suffered from a fungal disease called dogwood anthracnose, and its numbers are diminishing due to this plant disease. Sherry is asking a valid question, and the answer is that the Kousa or Japanese dogwood would be resistant to this disease. Another option would be to purchase a hybrid between the Kousa dogwood and our native dogwood.

The Kousa dogwood is like our flowering dogwood in a couple of ways. The Kousa is a small tree like our native dogwood, and it has similar flowers as our native tree although the petals have a different tapered shape.

210_fig_3_southern_mole_cricketjpgAdult form of the southern mole cricket.
Photo: Mississippi State University Extension Service.

Mole Cricket

A homeowner brought in two insect specimens for identification. AHA identified one of those insects as a mole cricket (MC). However, both went to Baton Rouge for an insect specialist to examine for positive identification.

There are three species of MC, and the specimen sent to Baton Rouge was southern mole cricket (SMC). MCs are pests of both lawns and pastures. An AgCenter publication describes the problems that these crickets cause, “Mole crickets burrow below the soil surface, breaking up plants and causing roots to dry out, eventually killing the turfgrass. Some species feed on leaves and roots as well.”

Cultural practices such as fertilizing, irrigating, setting correct mower height and dethatching will enable a healthy lawn to resist MC. There are several chemical pesticides labeled for controlling MC. Contact your local AgCenter agent for treatments of MC.

210_fig_4_velvet_or_cow_killer_antjpgVelvet or cow killer ant. Photo: Texas A&M Agrilife Extension.

Velvet Ant

The other insect sent to Baton Rouge for identification was a velvet ant (VA).

The VA isn’t an ant at all. It is wingless female wasp and has a painful sting. The male VA can fly and is stingless. According to Texas A&M Agrilife Extension, “Most [VAs] are solitary parasites of immature wasps, solitary bees and some other insects such as beetles and flies… They can occur in large numbers, sometimes on flowers of landscape plants. Larvae [of VAs] are parasites of white grubs.” The “take home” message is that this insect can be in your landscape, and so gardeners need to take care to avoid its painful sting. The orange-red color of its hair is a good warning sign.

Here is another comment from TAMU, “The common name, ‘cow killer,’ is thought to describe the painful sting these insects can inflict to man and animals, although it is doubtful that many cows are actually stung.”

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.

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

2/13/2020 7:38:06 PM
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