This is a comprehensive list of various biologicals and plant extracts commonly used as insecticides in organic agriculture. Please note that the availability and approved use of these substances may vary by region, so it is important to consult local regulations and certifications when considering their use.

Widespread use:

Bacillus thuringiensis (Bt): A naturally occurring soil bacterium that produces proteins toxic to specific insect larvae, including caterpillars, beetles, and mosquitoes.

Spinosad: Produced by a soil bacterium called Saccharopolyspora spinosa, it affects the nervous system of insects, particularly targeting pests like caterpillars, thrips, leafminers, and fruit flies.

Trichoderma spp.: A group of beneficial fungi that can suppress soil-borne pests, such as root rot pathogens and nematodes.

Neem oil (Azadirachta indica): Extracted from the seeds of the neem tree, it acts as a repellent, insect growth regulator, and disrupts feeding and reproduction in many insect pests.

Karanja oil (Pongamia pinnata): Extracted from the seeds of the karanja tree, it contains compounds like pongamol and karanjin, which have insecticidal properties. Karanja oil is known to repel and control a wide range of insect pests, including aphids, caterpillars, and mites.

Pyrethrum (Tanacetum cinerariifolium): Derived from the dried flowers of the pyrethrum daisy, it contains natural insecticidal compounds called pyrethrins, which affect the nervous system of insects.

Beauveria bassiana: A naturally occurring fungus that infects and kills a wide range of insect pests, including whiteflies, aphids, and beetles.

Metarhizium anisopliae: Another naturally occurring insect pathogenic fungus that targets a wide range of pests, including weevils, beetles, and grasshoppers.

Rotenone: Derived from the roots of several plants, including Derris and Lonchocarpus, it affects the mitochondria of insects and has contact and stomach poison properties.

Ryania (Ryania speciosa): Obtained from the stems and roots of the Ryania plant, it disrupts the digestive systems of insects, especially leaf-feeding caterpillars.

Sabadilla (Schoenocaulon officinale): Derived from the seeds of the sabadilla lily, it contains alkaloids that act as contact insecticides and affect insects’ nervous systems.

Pesticidal soaps: Made from fatty acids derived from plant oils, such as potassium salts of fatty acids, they disrupt the cell membranes of soft-bodied insects like aphids, mites, and whiteflies.

Horticultural oils: Also known as mineral oils or narrow-range oils, these petroleum-based oils suffocate insects by blocking their spiracles, used to breathe.

Chrysanthemum extract (Pyrethrum cinerariifolium): Similar to pyrethrum, it contains natural pyrethrins that affect the nervous systems of insects.

Quassia (Quassia amara): Derived from the bark of the Quassia tree, it acts as a stomach poison and repellent to various insects.

Tobacco (Nicotiana tabacum): Tobacco extracts, such as nicotine sulfate, are effective against aphids, thrips, and other insect pests.

Chile pepper (Capsicum spp.): Capsaicin, the active compound in chile peppers, can be used as a repellent and insecticide against various pests.

Garlic (Allium sativum): Garlic extract acts as a repellent and insecticide, deterring a wide range of insect pests.

Diatomaceous earth: Composed of fossilized remains of diatoms, it acts as an abrasive powder that damages the cuticle of insects, leading to dehydration and death.

Iron phosphate: Used primarily as a molluscicide against slugs and snails, it is considered safe for humans and other animals.

Sparingly used and less explored:

Kaolin clay: A fine, white powder derived from kaolinite clay, it forms a protective barrier on plant surfaces, repelling and reducing insect feeding damage.

Beauveria brongniartii: Another species of entomopathogenic fungus that targets various insect pests, including whiteflies, thrips, and beetles.

Trichogramma wasps: These tiny parasitic wasps lay their eggs inside the eggs of certain pests, such as moth and butterfly eggs, effectively controlling their populations.

Steinernema nematodes: Beneficial nematodes that parasitize and kill soil-dwelling pests like grubs, weevils, and root maggots.

Bacillus subtilis: A bacterium that produces antifungal compounds and enzymes, providing protection against fungal diseases that may indirectly benefit plants by reducing insect attraction.

Sesame oil (Sesamum indicum): It acts as a repellent and insect growth regulator against various pests, including aphids, whiteflies, and mites.

Tephrosia extract (Tephrosia vogelii): Derived from the leaves and stems of the Tephrosia plant, it contains rotenoids that have insecticidal and repellent properties.

Wormwood (Artemisia spp.): Extracts from wormwood plants contain volatile compounds that repel and deter insects like moths, aphids, and fleas.

Tobacco hornworm (Manduca sexta) extracts: Certain extracts from the tobacco hornworm larvae contain compounds that disrupt feeding and molting in insects.

Marigold (Tagetes spp.): Certain marigold species contain compounds that repel nematodes, aphids, and other insect pests.

Onion (Allium cepa) and garlic chive (Allium tuberosum) extracts: These extracts have repellent properties against various insects, including aphids and thrips.

Plant Oils and Extracts:

Citronella oil (Cymbopogon nardus): Extracted from certain species of grasses, it acts as a repellent against mosquitoes and other biting insects.

Lemon eucalyptus oil (Corymbia citriodora): Extracted from the leaves of the lemon eucalyptus tree, it acts as a repellent against mosquitoes and other biting insects.

Peppermint oil (Mentha piperita): Known for its strong scent, peppermint oil can deter and repel insects like ants, spiders, and mosquitoes.

Rosemary oil (Rosmarinus officinalis): Extracts from rosemary have insecticidal properties and can repel certain pests like cabbage worms and carrot flies.

Cinnamon oil (Cinnamomum verum): Cinnamon oil is a natural repellent and insecticide that can deter ants, flies, and mosquitoes.

Rosemary extract (Rosmarinus officinalis): Rosemary extract acts as a contact insecticide and repellent against various insect pests, including aphids, whiteflies, and mites.

Lemon grass oil (Cymbopogon citratus): Extracted from the leaves of lemon grass, it acts as a repellent against mosquitoes, ticks, and other biting insects.

Mint oil (Mentha spp.): Mint oil has insecticidal properties and can be effective against ants, aphids, and beetles.

Catnip (Nepeta cataria): Catnip extract can repel certain insect pests, including mosquitoes, aphids, and cockroaches.

Thyme oil (Thymus vulgaris): Thyme oil acts as a repellent and insecticide against various pests, including mosquitoes, ants, and flies.

Lavender oil (Lavandula spp.): Lavender oil has insecticidal properties and can be used to repel moths, fleas, and mosquitoes.

Tansy (Tanacetum vulgare): Tansy extracts can repel insects like mosquitoes, ants, and flies.

Feverfew (Tanacetum parthenium): Feverfew extracts have insecticidal properties and can repel aphids, mites, and whiteflies.

Clove oil (Syzygium aromaticum): Clove oil acts as a contact insecticide and repellent against various pests, including ants, mosquitoes, and beetles.

Lemongrass (Cymbopogon spp.): Lemongrass extracts can repel mosquitoes, ticks, and other biting insects.

Pennyroyal (Mentha pulegium): Pennyroyal extracts have insecticidal properties and can repel fleas, ticks, and mosquitoes.

Sage (Salvia spp.): Sage extracts can repel various insect pests, including moths, flies, and ants.

Yarrow (Achillea millefolium): Yarrow extracts can repel various insect pests, including mosquitoes, aphids, and beetles.

Pine oil (Pinus spp.): Pine oil acts as a contact insecticide and repellent against pests like fleas, ticks, and mites.