Extension Master GardenerSM Volunteers of Buncombe County

pest control

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

 

 

Pest Facts: Hemlock Woolly Adelgid (HWA)

Just visit a Western North Carolina forest to see how much destruction this non-native invasive insect pest has caused—and is still causing—on the native Carolina hemlocks (Tsuga caroliniana) and Eastern hemlocks (Tsuga canadensis)! After our recent rains, this is a good time to treat your hemlocks if you see a white cottony substance on your hemlocks.

Hemlock Woolly Adelgid

History

  • HWAs were discovered in Shenandoah National Park in northern Virginia in 1988, likely when crawlers clung to the legs and feathers of migrating birds, such as the black-throated green warbler and solitary vireo that visit or nest in hemlock trees.
  • HWAs were discovered on hemlocks in North and South Carolina in late 2001 and early 2002.

HWA (Adelges tsugae) Life Cycle:

  • HWAs hatch from eggs and then go through a crawler stage—almost invisible to the naked eye. These crawlers cannot fly on their own but can drift in the air from tree to tree, and cling to the legs and feathers of migrating birds.
  • After settling on host trees, the HWAs insert a bundle of mouthparts at the base of a needle and spend the rest of their lives—a few months—sucking nutrients out of the tree.
  • The name “woolly” comes from the fact that adult HWAs are covered with a protective white fluff once they settle.
  • The HWA goes through two generations a year (one in March and one in October in Western North Carolina) and each female—even without being fertilized by a male—can lay between 100 to 300 eggs.
  • This reproductive process is called “parthenogenesis”—the offspring are genetically identical clones of their mother.

Controls

Chemical: Registered pesticides containing imidacloprid or dinotefuran are the most effective chemical treatments for control of HWAs. These are applied as a soil injection or trunk spray. These insecticides are water soluble and move into the tree’s vascular system along with water. Dinotefuran has a faster uptake, but imidacloprid has a longer residual protection. Control of HWAs using imidacloprid can last for 4-5 years. Dinotefuran may require retreatment within 2 years.

Biological:

The species that has so far shown the most promise as a biological control agent is Laricobius nigrinus, a predator beetle native to the Pacific Northwest. L. nigrinus is active from October to March; both adults and larvae will consume all stages of HWAs: eggs, nymphs and adults.

After exhaustive evaluation in quarantine labs, it was cleared by the USDA for use as an HWA biocontrol in the eastern United States in 2000 and has been released in NC since 2003.

Original Article by Glenn Palmer, Extension Master GardenerSM Volunteer, Revised by Bob Wardwell, Extension Master GardenerSM Volunteer

Hemlock Restoration Initiative https://savehemlocksnc.org/

National Park Service Great Smoky Mountains Hemlock Woolly Adelgid

https://www.nps.gov/grsm/learn/nature/hemlock-woolly-adelgid.htm

University of Massachusetts HWA Fact Sheet https://ag.umass.edu/landscape/fact-sheets/hemlock-woolly-adelgid

Pest Alert: Basil Downy Mildew Found in Western North Carolina – July 22, 2019

Basil downy mildew has been confirmed on the variety ‘Genovese’ in the NC State University research plots in Haywood County, North Carolina.

Basil Downy Mildew Spores on Underside of Leaf
Basil Downy Mildew

Basil downy mildew characteristics

  • Pathogen: Basil downy mildew is caused by the fungus-like oomycete pathogen Peronospora belbahrii.
  • Host crop: Basil (Ocimum basilicum)
  • Host parts affected: Leaves are severely affected, which can result in yield reduction or plant death.

 Identification

The disease typically begins in June and lasts throughout the growing season. Symptoms include yellowing or browning of leaves, which may be mistaken for nutritional problems. Infected leaves have many dark spores on the underside of infected leaves that can be seen without a microscope or hand lens.

  • High-humidity and moisture—6 to 12 hours of moisture from morning dew, rain, or overhead irrigation.
  • Cool temperatures (60°F).

Prevention

The disease has not been found on the resistant sweet basil varieties ‘Thunderstruck,’ ‘Devotion,’ ‘Passion,’ and ‘Obsession.’ Planting these resistant varieties or pathogen-free seed of other varieties is essential to prevent basil downy mildew.

Some basil types are less susceptible than sweet basil varieties. Researchers have found red basil (‘Red Leaf’ and ‘Red Rubin’), Thai basil (‘Queenette’), lemon basil (‘Lemon,’ ‘Lemon Mrs. Burns,’ ‘Sweet Dani Lemon Basil’), lime basil (‘Lime’), and spice basil (‘Spice,’ ‘Blue Spice,’ ‘Blue Spice Fil,’ ‘Cinnamon’) to have less severe downy mildew symptoms.

In addition to infected seed. disease also spreads from airborne spores of Peronospora belbahrii. Help control by watering early in the mornings, so foliage dries quickly, and allowing enough space between plants to increase air circulation.

Disease control for home gardeners

Be diligent in checking basil leaves for downy mildew. Fungicides are most effective when applied in a preventive, weekly spray program. Products containing the active ingredients copper or chlorothalonil (‘Daconil’ is the trade name of one product with chlorothalonil) are the only effective products available to home gardeners. Apply to achieve good coverage on both sides of the foliage and apply the products before disease begins.

 For more information:

Pest Alert: https://plantpathology.ces.ncsu.edu/2019/07/basil-downy-mildew-found-in-western-north-carolina-july-22-2019/

Basil Downy Mildew: https://content.ces.ncsu.edu/basil-downy-mildew

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

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