Extension Master GardenerSM Volunteers of Buncombe County

Pest Management

Managing Garden Pests: Insecticidal Soap?

 

Insecticidal Soap example-No Product Endorsement is intended.

Do you prefer organic pest control? Have you seen lots of homemade pest remedies on Facebook or gardening websites that you wonder if you should try? Then you’ve probably heard of insecticidal soap! What you may not know is that:

  • Many things we think of as “soaps” aren’t really soaps
  • Not all soaps are effective as insect killers
  • Many soaps may damage or even kill your plants rather than your pests!

So what ARE insecticidal soaps?

Insecticidal soaps are soap products registered as insecticides. According to Raymond Cloyd, Extension Entomologist, Kansas State University, they are “‘reduced risk’ insecticides…used in certain situations because they leave minimal residues, are less toxic to humans, and are short-lived in the environment because they degrade rapidly.” He notes that “Soap is a general term for the salts of fatty acids.”

The Environmental Protection Agency only registers potassium salts of fatty acids as active ingredients of insecticidal soaps. Why does this matter? Other salts and other fatty acids in soaps aren’t necessarily effective as insecticides—and may be harmful to plants!

Should you use an insecticidal soap for pest control?

First, identify your pest! Not all insects are pests and not all pests are controlled with insecticidal soaps. Then decide if your plants will benefit from using insecticidal soap:

  • Will the affected plants tolerate insecticidal soap? Read the label to be sure the product is registered for use on the garden plants that pests are threatening.

  • Insecticidal soap label.
  • Do your plants need intervention—how much pest damage can you—and your plants—tolerate?

  • Adult Ladybug eating an aphid. Do you need an insecticide?

Commercially produced insecticidal soap sprays can effectively kill “soft-bodied” pests they come in contact with, such as:

  • Aphids,
  • Leafhoppers,
  • Mealybugs,
  • Mites,
  • Scales,
  • Thrips, and
  • Whiteflies
  • Thrip damage on onions. Is this sufficient to warrant use of an insecticide?

    Whiteflies: Does this infestation justify using an insecticide?

Insecticidal soaps are most effective on the early stages of pest development—such as larvae—and safest when applied only to plants listed on the product label when those plants are not under too much stress. In other words, use insecticidal soap when pests first start to appear in sufficient numbers to become a threat to your plants.

Ladybug larva eating aphids. Insecticidal soap will kill both the ladybug larva and the aphids.

Insecticidal soaps can’t:

  • Control soft-bodied insects after the spray dries on the plant—only spray when you can see the pests!
  • Control “hard-bodied” insects, such as beetles.
  • Distinguish between beneficial insects and pests!

Are all insecticidal soaps organic?

Check the Organic Materials Review Institute (OMRI) list for registered organic pesticides. Many pesticides that contain potassium salts of fatty acids contain other active ingredients that are not organic.

 What about those recipes for insecticidal soap?

Many “soaps” you have in your home are detergents, not soaps! These cleaning products may kill your plants rather than your pests. Even those soap products on your shelf that might have some insecticidal properties may damage your plants or may not be as effective as products registered for garden use. If asked, the makers of popular soap products will emphasize like we do—read the label! If the product isn’t registered for garden use, don’t use it!

Article by Buncombe County Extension Master GardenerSM Volunteers

For more information:

Raymond Cloyd, “Fundamentals of Using Soaps as Insecticides”:

https://blogs.k-state.edu/kansasbugs/2020/06/12/fundamentals-of-using-soaps-as-insecticides/

OMRI Products List: https://www.omri.org/omri-lists/download

How to choose a pesticide: http://npic.orst.edu/pest/select.html

Discussion of pest tolerance: https://extension.entm.purdue.edu/radicalbugs/default.php?page=decision_making

Organic gardening: https://content.ces.ncsu.edu/extension-gardener-handbook/17-organic-gardening#insects

 

 

Non-Native Invasive Plants: Japanese Spirea

Japanese Spirea

What is Japanese spirea?
Gardeners imported Japanese spirea (Spiraea japonica) to the United States in 1870 for use in Victorian-era landscapes. The easy-to-grow shrubs with the compact habit and pink flowers remained a favorite. Now Japanese spirea is one of many Asian shrubs threatening the ecosystems of our native southern forests.

Why is it a problem?
Japanese spirea has small seeds that wash away and rapidly take over disturbed areas; they are especially a problem when they reach stream banks. Seeds may also arrive in fill dirt used in home construction.

Once established, Japanese spirea forms dense stands that outcompete the native forest flora. Seeds from Japanese spirea can last for years in the soil, making the spread difficult to control. Note that although Japanese spirea is not yet on North Carolina’s statewide list of invasive plant species, it is specifically noted as an invasive plant in Buncombe County and the Great Smoky Mountains National Park.

Some cultivars of the invasive Japanese spirea have golden leaves like this ‘Goldflame’ spirea

How Can I Help?
Don’t plant Japanese spirea! Consider using native plants in your landscape. Some alternatives are:
• The native spireas, white meadowsweet (Spiraea alba),

The native meadowsweet has white flowers.

• sweet pepperbush (Clethra alnifolia),
• silky dogwood (Cornus amomum),
• leatherleaf (Dirca palustris),
• Virginia sweetspire (Itea virginica),
• ninebark (Physocarpus opulifolius).

This native clethra has pink flowers.

Consider removing existing plants.
If you can’t easily dig up your planting, cutting back and repeated mowing can help eliminate unwanted shrubs. Be sure to keep cutting back to prevent seed production!
For large infestations, herbicides containing triclopyr or glyphosate are effective. Be careful to follow label directions!

Article by Barbara Hayes, Extension Master GardenerSM Volunteer

For more information:
Weed of the Week:https://www.invasive.org/weedcd/pdfs/wow/japanese-spiraea.pdf

Distribution of Japanese spirea:https://www.invasiveplantatlas.org/subject.html?sub=3076

Invasive exotic plants in the Great Smoky Mountains National Park:https://www.nps.gov/grsm/learn/nature/non-natives.htm

Non-Native Invasive Plants: Bamboo—The Plant We All Love to Hate!

A visitor to the Extension Master Gardener office told me he had a plant to identify that was too big to bring inside—that got my interest. In the back of his truck he had a grass-like plant over 10 feet tall with hollow stems!

 Bamboo or river cane?

I was looking at either a running type of bamboo (Phyllostachys spp.) or another form of bamboo: river cane (Arundinaria spp.). The difference between the two? One is an extremely aggressive invasive native and the other is a native.

 Phyllostachys aurea is a bamboo species of the ‘running bamboo’ type. It is commonly known by the names fishpole bamboo and golden bamboo.  This is the species most widely seen in the landscape. A related species is Phyllostachys nigra—black bamboo—is also widely cultivated and invasive! They both form dense—almost impenetrable—thickets that crowd out all other plants.

Invasive Bamboo

Arundinaria is the only bamboo native to North America, found in the south-central and southeastern United States. It is tree-like, growing to heights up to 26 ft. It has distinctive fan-like cluster of leaves at the top of new stems called a top knot. Arundinaria gigantea, commonly known as river cane, is a woody plant native to North Carolina.  River cane communities occur on floodplains, bogs, along streams and rivers and in riparian woods.

River Cane

It became obvious to me that my visitor just wanted it gone from his yard!

Dr. Joseph C. Neal, Department of Horticultural Science, at NC State University, discusses three techniques for dealing with bamboo in the publication “Controlling Bamboo in Landscape Plantings.”

Removal

To eliminate a planting completely requires physically removing as much of the top growth and root mass as possible—this will require power equipment for large infestations! Bamboo will regenerate from any small rhizomes left behind so long-term follow-up will typically require the use of herbicides or planting the area in lawn:

  • Chemical control involves spraying with a post-emergent, non-selective herbicide such as glyphosate and may require repeated spraying whenever new growth occurs.
  • Convert to lawn avoids the use of herbicides and relies on the fact that bamboo will not tolerate frequent mowing. This works only if you mow the entire area! If you don’t eliminate the entire stand, new shoots will keep moving in from the remaining plants.

Containment

  • If you want to contain a bamboo planting, you can install a barrier— concrete, metal, plastic, or pressure-treated wood—installed at least 18 inches deep that slants outward and rises at least a couple of inches above the ground. Because barriers only deflect rhizomes rather than prevents them from growing, you will need to inspect the barrier at least yearly to remove any new rhizomes.

Regardless of which method of control you choose, eradicating a bamboo infestation requires intensive effort over several years.  Of course, the best way to prevent bamboo from becoming a weed is to avoid planting the invasive, spreading-type bamboos in the first place—and ask your neighbors to avoid it, too!

 Article by Bob Wardwell, Extension Master GardenerSM Volunteer

Controlling bamboo in landscape plantings:

https://content.ces.ncsu.edu/controlling-bamboo-in-landscape-plantings

Identifying Native Bamboo: www.namethatplant.net/article_nativebamboo.shtml

More about river cane:

http://www.indefenseofplants.com/blog/2017/6/26/north-americas-native-bamboos

Contact Us

Buncombe County Extension Office
49 Mount Carmel Road
Asheville, NC 28806
Helpline 828-255-5522

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