** See Definition of Organic

The listing of insecticides that follow were called “near organic” because of ongoing discussion about their discussion and debate about their “organic” status. Many are “of natural origin”, but some (e.g., boric acid, silica dioxide or diatomaceous earth/D.E.) contain no carbon molecules so they are technically inorganic molecules. Thus when used in an “orgainic” pest control program, are they “inorganic organics”? Others, like insecticidal soap products are allowed for use in certified state and federal organic food production programs, but are synethesised by a chemical reaction involving potassium salts and long-chained fatty acids, thus not “of natural origin”. The following information was extracted and modified from Henn, T. and R. Weinzieri, 1989; Larson, L.L., et al., 1985; and Morgan, D.P., 1989):

insecticidal soaps* (M-pede®, Safer Insecticidal Soap® and others) – Insecticidal soaps generally are not considered to be botanical insecticides, although the oils from which they are produced may be of plant origin. In chemical terms, insecticidal soaps (and all soaps in general) are made from the salts of fatty acids. Fatty acids are the principle components of the facts and oils found in animals and plants. Numerous studies have been conducted to correlate insecticidal activity with the physical structure of fatty acids, and certain acids have been determined to be most insecticidal. Oleic acid, present in high quantities in olive oil and in lesser amounts in other vegetable oils, is especially effective. Safer® soaps, the most common currently available insecticidal soaps, contain potassium oleate (the potassium salt of oleic acid) as the active ingredient.

* Note: some soaps and paraffinic oils can be plant derived

Mode of action. Despite many years of use, the mode of cation of insecticidal soaps still remains somewhat unclear. Although the action of soaps involves some physical disruption of the insect cuticle (the outer body covering), additional toxic action is suspected. Some evidence indicates that soaps enter the insect’s respiratory system and cause internal cell damage by breaking down cell membranes or disrupting cell metabolism. Soaps also exert some non-lethal developmental effects on immature insects.

Mammalian toxicity. The mammalian toxicity of insecticidal soaps is basically the same as that of any soap or detergent. Ingestion causes vomiting and general gastric upset, but has no serious systemic consequences. Insecticidal soap concentrates may contain ethanol (up to 30%), which causes intoxication at doses above several ounces; however, vomiting is likely to clear most of the alcohol from the system before it is absorbed into the blood-stream. Externally, soaps are irritating to eyes and mucous membranes and have drying effects on skin.

Some insecticidal soap products contain additional insecticidal compounds such as pyrethrins or citrus oil derivatives. These combination products have a higher toxicity then products containing only soap, and their additional toxic effects depend on the kinds of insecticides added.

diatomaceous earth (D.E.)(SiO₂) – Crushed silica-containing shells of microorganisms called diatoms, the sharply serrated crystals scarify an insect’s waxy outer coat destroying its moisture balance. Inhalation of diatomaceous earth dust can cause silicosis of the lungs.

silica gel – silica aerogel + ammonium fluosilicate to 3% fluorine content (Dri-Die®) absorbs oils (oil absorption 40-70%) leading to moisture imbalance.

sulfur – Elemental sulfur has been used as an acaricide/miticide and fungicide on orchard, ornamental, vegetable, grain and other crops. It is prepared as a dust in various particle sizes. Elemental sulfur is irritating to the skin, and airborne dust is irritating to the eyes and the respiratory tract. In hot, sunny environments, there may be some oxidation of foliage-deposited sulfur to irritating gaseous sulfur oxides, which are very irritating to the eyes and respiratory tract. Ingested sulfur powder causes catharsis (dehydration and electrolyte depletion caused by diarrhea), and has been used medically (usually with molasses) for that purpose. Some hydrogen sulfide is formed in the large intestine and may present a degree of toxic hazard. However, an adult has survived ingestion of 60 grams. Ingested colloidal sulfur is efficiently absorbed by the gut and is promptly excreted in the urine as inorganic sulfate.

boric acid (B(OH)₃ – registered for control of cockroaches and some ant species. It has been used as an ant bait ingredient, but can cause phytotoxicity when applies to the landscape.

arsenic – Arsenic is a natural element having both metal and nonmetal physical/chemical properties. Sodium arsenite, calcium arsenite, sodium arsenate, calcium arsenate and zinc arsenate are registered have been used as insecticides, particularly as ant baits.

vegetable oils (neem oil, soybean oil, citrus oil and others) – plant derived oils can suffocate insects coated with or drenched in these diluted liquids. Some are EPA registered products, many are sold as 25(b) products and some are used as home remedies.
* Note: some soaps and paraffinic oils can be plant derived

petroleum derived products:

• Tangle foot – not a registered insecticide
• Dormant oil
• Superior oil (Fertilome® Natural Guard Superior Oil is 98% paraffinic oil and is registered for obscure scale)
• Summer oil
• Horticultural oil (paraffinic oils)*
• Mineral oil – not registered as an insecticide

fermentation products (exudates from microorganisms, isolated and purified)

• avermectin (Avid®, Ascend®)
• spinosad

insect growth regulators (synthetic)

• Juvenoids – synthetically produced molecules that mimic the effects of the naturally occurring insect juvenile hormone fenoxycarb (Logic®)
• kinoprene (Enstar®)
• methoprene (Precore®)
• hydroprene (Gencore®)
• Chitin synthesis inhibitors – synthetic or naturally occurring molecules that inhibit the production of the exoskeleton element, chitin, following a molt diflubenzuron (Dimilin®)
• azadractin (derived from neem seed extract)

Pyrethrin analogs (synthetic) – resmethrin, tetramethrin, sumethrin, pyrethroids (fenvalerate, permethrin, bifenthrin, cypermethrin, fenpropathrin, and others

Pheromones (synthetic) – not registered as insecticides

Table 2. Registered Uses of Insecticidal Soaps and Oils

SOURCES OF INFORMATION

Henn, T. and R. Weinzieri. 1989. Botanical insecticides and insecticidal soaps. Circular 1296. Cooperative Extension Service. University of Illinois, Urbana-Champaign. 18 pp.

Henn, T. and R. Weinzieri. 1990. Beneficial insects and mites. Circular 1298. Cooperative Extension Service. University of Illinois, Urbana-Champaign. 24 pp.

Larson, L. L., E. E. Kenaga and R.W. Morgan. 1985. Commercial and experimental organic insecticides. Entomological Society of America. 105 pp.