Roots, Shoots, Fruits & Flowers: Rhino Grub, Clover Worm & Grass-Carrying Wasp

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A closeup image of a large rhino grub. Photo: George Giltner.

Large rhino grub

n the last column of RSFF, Paige asked about some small grubs in a container garden. There grubs were probably the brood of June bugs. George sent in his comments and his own image of a rhino grub, “Paige may want to measure her grubs for a relative ID. This Rhino beetle larvae is in my compost. [It] will stretch out at around 2 inches. [It] grinds my compost at a rapid rate and infuses it with beneficial microbes that allow nutrients to make super plants [and it is a beneficial insect larva]. [It] lives on organic matter only, not [feed on] plant roots, so [it] is a large grub, not the smaller one-inch June bug larvae that are harmful.”

If you find a large grub, most likely in your compost, then you likely have a helpful rhino grub, and it becomes the fierce-looking rhinoceros beetle. Despite its threatening size and shape, it is a harmless beetle. The benefit of this grub lies in its ability to speed up decomposition of vegetation.

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A clover worm on an oak leaf. Photo: Peggy Kessler.

Clover worm

Peggy shared a concerning email with a clear picture, “[I] found this active green caterpillar on several green leaves in my vegetable garden. Any idea what it is? What do I need to do to keep it from eating my garden up? All suggestions must be honeybee friendly🐝🐝🐝.”

AHA consulted with Dr. Sebe Brown, an insect specialist in row crops, and he shared, “It looks like a clover worm of some sort. They are easy to kill with a foliar Bt [Bacillus thuriengensis] product such as Dipel or Javelin.” These products use a microscopic pathogen to specifically treat caterpillars that become moths. Another AgCenter insect specialist treated honeybees with Bt to study the bee’s susceptibility, and Bt failed to kill or harm the bees.

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A nest made by a grass-carrying wasp. Photo: Christy Frederic.

Nest made by a grass-carrying wasp

One of the rewarding aspects of writing RSFF is learning from readers. Christy shared an image and some information about a native insect, “I noticed a bunch of dry grass in the window screen channels of several windows. I learned these are the nests of harmless, native grass-carrying wasps (GCW). [ I am] so glad I am not too old to learn something new about what is happening in my own backyard! “

According to Michigan State University Extension, the GCW is a solitary insect raising her brood in a nest she built. GCW will also use old brood galleries of other insects or hollow plant stems for nesting.

A native of North America, GCW feeds on tree crickets during brood rearing. During most of its adult life, GCW pollinates flowers and feeds on nectar. It is harmless unless a person decides to handle it.

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.”

4/14/2020 2:59:41 PM
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