Insecticidal soap is defined as any of the potassium

Potassium

Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...

 fatty acid

Fatty acid

In chemistry, especially biochemistry, a fatty acid is a carboxylic acid with a long unbranched aliphatic tail , which is either saturated or unsaturated. Most naturally occurring fatty acids have a chain of an even number of carbon atoms, from 4 to 28. Fatty acids are usually derived from...

 soaps used to control many plant pests. Insecticidal soap is typically sprayed on plants in the same manner as other insecticides. Insecticidal soap works only on direct contact with the pests. The fatty acids disrupt the structure and permeability of the insect cell membranes. The cell contents are able to leak from the damaged cells, and the insect quickly dies.

Benefits of insecticidal soap

Insecticidal soap works best on soft-bodied insects such as aphids, mealybugs, spider mites, thrips

Thrips

Thrips are tiny, slender insects with fringed wings . Other common names for thrips include thunderflies, thunderbugs, storm flies, thunderblights, and corn lice...

, and whiteflies. It can also be used for caterpillars, and leafhoppers, though these large bodied insects can be more difficult to control with soaps alone. Many pollinators and predatory insects such as Lady beetle adults, bumble bees, and syrphid flies are relatively unaffected.

Toxicity

Soaps have low mammal

Mammal

Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

ian toxicity. However, they can be mildly irritating to the skin or eyes.

Insecticidal soaps may cause phytotoxicity

Phytotoxicity

Phytotoxicity is a term used to describe the degree of toxic effect by a compound on plant growth. Such damage may be caused by a wide variety of compounds, including trace metals, pesticides, salinity, phytotoxins or allelopathy.-Urea and urine:...

 (toxic to the plant) symptoms, such as yellow or brown spotting on the leaves, burned tips or leaf scorch on certain plants. In general, some cole crops and certain ornamentals are sensitive to burn caused by soaps. Multiple applications in a short time interval can aggravate phytotoxicity. In addition, water conditioning agents can increase phytotoxicity. A small spray strip should be applied and observed before a full-scale application is made if there is a question concerning sensitivity. Mountain ash

Mountain Ash

Mountain Ash is a name used for several trees, none of immediate relation. It may refer to:* Eucalyptus regnans, the tallest of all flowering plants and other floral species* Fraxinus texensis, an ash tree species in Texas...

, Japanese maple, jade plant

Jade plant

Commonly known as jade plant, friendship tree, lucky plant or Money Plant, Crassula ovata is a succulent plant with small pink or white flowers. It is native to South Africa, and is common as a houseplant worldwide...

, lantana

Lantana

Lantana is a genus of about 150 species of perennial flowering plants in the verbena family, Verbenaceae. They are native to tropical regions of the Americas and Africa but exist as an introduced species in numerous areas, especially in the Australian-Pacific region. The genus includes both...

, gardenia

Gardenia

Gardenia is a genus of 142 species of flowering plants in the coffee family, Rubiaceae, native to the tropical and subtropical regions of Africa, southern Asia, Australasia and Oceania....

, bleeding heart

Dicentra

Dicentra is a genus of 8 species of perennial herbaceous plants in the fumitory family, many with heart-shaped flowers, native to eastern Asia and North America.-Description:...

 and crown of thorns

Euphorbia milii

Euphorbia milii is a woody, succulent species of Euphorbia native to Madagascar. The species name commemorates Baron Milius, once governor of Réunion, who introduced the species to France in 1821...

 are known to be sensitive to soap. Certain cultivar

Cultivar

A cultivar'Cultivar has two meanings as explained under Formal definition. When used in reference to a taxon, the word does not apply to an individual plant but to all those plants sharing the unique characteristics that define the cultivar. is a plant or group of plants selected for desirable...

s of azalea

Azalea

Azaleas are flowering shrubs comprising two of the eight subgenera of the genus Rhododendron, Pentanthera and Tsutsuji . Azaleas bloom in spring, their flowers often lasting several weeks...

, poinsettia

Poinsettia

Euphorbia pulcherrima, commonly known as Zack Wood or noche buena, is a species of flowering plant indigenous to Mexico and Central America. The name "poinsettia" is after Joel Roberts Poinsett, the first United States Minister to Mexico, who introduced the plant into the US in 1825...

, begonia

Begonia

Begonia is a genus in the flowering plant family Begoniaceae and is a perennial. The only other members of the family Begoniaceae are Hillebrandia, a genus with a single species in the Hawaiian Islands, and the genus Symbegonia which more recently was included in Begonia...

, impatiens

Impatiens

Impatiens is a genus of about 850–1,000 species of flowering plants, widely distributed throughout the Northern Hemisphere and tropics. Together with the puzzling Hydrocera triflora, this genus makes up the family Balsaminaceae...

, fern

Fern

A fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...

s, palm

Arecaceae

Arecaceae or Palmae , are a family of flowering plants, the only family in the monocot order Arecales. There are roughly 202 currently known genera with around 2600 species, most of which are restricted to tropical, subtropical, and warm temperate climates...

s and succulents may also be sensitive. When uncertain, spot treat a portion of the plant, and wait at least 24 hours to see if any phytotoxic symptoms develop before treating an entire group of plants. Plants under drought

Drought

A drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region...

 stress, young transplants, unrooted cuttings and plants with soft young growth are more likely to develop phytotoxic symptoms and should not be treated with soap. Soap mixed in hard water may be less effective and more toxic to the treated plants. A precipitate may be formed when the metal ions (e.g., Calcium

Calcium

Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

, iron

Iron

Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 or magnesium

Magnesium

Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...

) found in hard water bind to the fatty acids in the soap.

Rates

The concentration of the spray is more important than the amount of soap applied. Usually insecticidal soaps are used as a 2% solution. If water is increased or decreased, then the amount of soap must be increased or decreased accordingly to avoid phytoxicity.

Pests controlled

Insecticidal soaps are used against soft bodied insects and mites such as aphid

Aphid

Aphids, also known as plant lice and in Britain and the Commonwealth as greenflies, blackflies or whiteflies, are small sap sucking insects, and members of the superfamily Aphidoidea. Aphids are among the most destructive insect pests on cultivated plants in temperate regions...

s, thrips, white flies, spider mite

Spider mite

Spider mites are members of the Acari family Tetranychidae, which includes about 1,200 species. They generally live on the under sides of leaves of plants, where they may spin protective silk webs, and they can cause damage by puncturing the plant cells to feed...

s and immature leafhopper

Leafhopper

Leafhopper is a common name applied to any species from the family Cicadellidae. Leafhoppers, colloquially known as hoppers, are minute plant-feeding insects in the superfamily Membracoidea in the order Hemiptera...

s. Insecticidal soaps have been about 40-50% effective against these pests.

Soap sprays, alone or in combination with horticultural oil

Horticultural oil

Horticultural Oils or Narrow Range Oils are lightweight oils, either petroleum or vegetable based. They are used in both horticulture and agriculture, where they are applied as a dilute spray on plant surfaces to control insects and mites...

s or botanical oils, are also valuable in the management of certain plant diseases, most notably powdery mildew

Powdery mildew

Powdery mildew is a fungal disease that affects a wide range of plants. Powdery mildew diseases are caused by many different species of fungi in the order Erysiphales. It is one of the easier diseases to spot, as its symptoms are quite distinctive. Infected plants display white powdery spots on the...

. Repeated applications may be necessary to adequately control high populations of pests.

See also

• Ecologic pesticides and herbicides
• Insect trap
  Insect trap
  Insect traps are used to monitor or directly reduce insect populations. They typically use food, visual lures, chemical attractants and pheromones as bait and are installed so that they do not injure other animals or humans or result in residues in foods or feeds. Visual lures use light, bright...
  
  
• List of repellent plants
• List of beneficial weeds
• Organic farming
  Organic farming
  Organic farming is the form of agriculture that relies on techniques such as crop rotation, green manure, compost and biological pest control to maintain soil productivity and control pests on a farm...
  
  
• Biological pest control
  Biological pest control
  Biological control of pests in agriculture is a method of controlling pests that relies on predation, parasitism, herbivory, or other natural mechanisms...