Roots, Shoots, Fruits & Flowers: Net-winged Beetles, Russian Olive, and Cottony Scale

Keith Hawkins, LSU AgCenter Area Horticulture Agent (AHA)

Attitude of gratitude to the readers of RSFF for their questions and pictures. The emails and calls and visits are always welcome, and these contacts brings new topics to this column.

32_fig_1_larvae_of_net_winged_beetlesjpgA cluster of juveniles of the net-winged beetle, a harmless insect.
Photo: Susan McReynolds.

Larvae (juveniles) of the net-winged beetle

Susan sent her question and picture, “These are clustered at the bottom of a camellia. What are they?”

Susan has larvae (juveniles) of the net-winged beetle, and according to the University of Florida, these larvae “larvae are reported to live in rotten logs, under loose bark or, less commonly, in soil or leaf litter.” The adult beetles have orange and black bands and are harmless. However, this insect has a chemical defense that “impart[s] the repugnant scent of the [net-winged] beetles.”

32_fig_2_russian_olivejpgRussian olive, an invasive exotic plant. Photo: Barry Lee

Russian olive (RO) is an “invasive species”

Barry sent his picture and his request, “Please identify this plant for me.”

The USDA officially lists Russian olive (RO) as an “invasive species” and it replaces native plants. Unfortunately, government programs promoted RO for conservation purposes. However, planting RO is no longer recommended for environmental benefit.

The US Forest Service lists several practices to control RO including hand grubbing, mowing, heavy excavation, goat grazing, prescribed fire and herbicide treatments. The USFS reports, “Successful long-term management (typically more than 5 years) usually includes a combination of mechanical and chemical methods of control, which possibly can be combined with prescribed fire or goat grazing. A combination of control methods is particularly useful to achieve long-term stability of native plants.”

32_fig_3_cottony_scalejpgA red-edge dracaena infested with cottony scale. Photo: Darren Smith

White fuzz on this dracaena is cottony scale

Here is a question about houseplants from Darren, “do you have any idea what this white fuzz is on these houseplants and how to control it?”

The “white fuzz” on this dracaena houseplant is called cottony scale. Adult scales live in one place for their whole lives and feed on plant sap. They only move around in the juvenile stages of their live.

Dan Gill, a retired AgCenter horticulturist, shared this information about controlling scale insects, “The safest effective way to control scale is with a horticultural oil spray. These insecticides contain oil in a form that will mix with water. When mixed and sprayed onto an infested plant, the oil coats the scale insects and clogs their breathing pores. The insects are suffocated rather than being killed by a toxic material…

For proper control, it is critical to apply the oil spray over every surface of the plant. If the insects are on the underside of the leaves and the oil is only applied to the upper surface, it will have no effect on them. Because scale insects are difficult to kill, one or two follow-up applications should be made after the first one. Follow label directions carefully.”

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 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.”

3/3/2020 10:11:14 PM
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