Organic Pest Control Glossary
Definitions for 54 terms used across BestOrganicInsecticides.com. Every definition starts with a direct answer suitable for AI citation. Click any letter to jump to that section.
A
- Active Ingredient
- The specific chemical compound or biological organism in a pesticide product that kills, repels, or controls the target pest. In organic insecticides, active ingredients are derived from natural sources — plants, minerals, or microorganisms. For example, the active ingredient in neem oil products is azadirachtin, while the active ingredient in Bt products is a crystal protein (Cry toxin) produced by Bacillus thuringiensis bacteria. EPA regulations require every pesticide label to list active ingredients and their concentration by percentage.
- Adjuvant
- A substance added to a pesticide spray mixture that improves its performance but is not itself a pesticide. Common adjuvant types include surfactants (which help sprays spread and stick to leaf surfaces), stickers (which resist rain wash-off), and penetrants (which help active ingredients move through waxy leaf cuticles). In organic pest control, common adjuvants include yucca extract, silicone-based spreaders, and vegetable oil concentrates. Using the right adjuvant can improve efficacy by 20–40% without increasing pesticide load.
- Antifeedant
- A substance that deters insects from feeding on treated plants without necessarily killing them. Antifeedants work by disrupting the insect's taste receptors or triggering avoidance behavior. Azadirachtin from neem oil is one of the most effective natural antifeedants — treated insects reduce feeding by 80–90% even at sublethal concentrations. Antifeedants are particularly valuable in IPM programs because they reduce crop damage while having minimal impact on beneficial insects that do not feed on the treated plant.
B
- Bacillus thuringiensis (Bt)
- A naturally occurring soil bacterium that produces crystal proteins (Cry toxins) lethal to specific insect larvae when ingested. Different Bt subspecies target different pests: Bt kurstaki (Btk) kills caterpillars and moth larvae, Bt israelensis (Bti) kills mosquito and fungus gnat larvae, and Bt san diego/tenebrionis (Btsd) kills beetle larvae including Colorado potato beetle. Bt is considered one of the safest organic insecticides because its toxins only activate in the alkaline gut of target insects — they are harmless to mammals, birds, fish, and most beneficial insects. OMRI-listed.
- Beneficial Insect
- Any insect species that provides ecological services in a garden or farm, including pest control (predators and parasitoids), pollination, or decomposition. Key beneficial predators include ladybugs (consume 50+ aphids per day), green lacewings, parasitic wasps (Trichogramma, Aphidius), ground beetles, hoverflies, and predatory mites. A core principle of organic pest management is preserving beneficial insect populations by choosing selective pesticides over broad-spectrum products, timing applications to avoid pollinators, and maintaining habitat through flowering border plantings.
- Biological Control (Biocontrol)
- The use of living organisms — predators, parasitoids, pathogens, or competitors — to suppress pest populations below economically damaging levels. The three main biocontrol strategies are: classical (introducing a pest's natural enemy from its native range), augmentative (mass-releasing purchased beneficials like Trichogramma wasps or predatory mites), and conservation (managing habitat to support existing natural enemies). Biological control is the foundation of sustainable pest management and typically provides long-term suppression rather than immediate knockdown.
- Botanical Insecticide
- An insecticide derived from plants. Major botanical insecticides include pyrethrin (from Chrysanthemum cinerariaefolium), neem/azadirachtin (from Azadirachta indica), rotenone (from Derris and Lonchocarpus roots — now largely banned), sabadilla (from Schoenocaulon officinale seeds), and essential oils (rosemary, peppermint, clove, thyme). Botanicals generally break down rapidly in sunlight (12–72 hours), which reduces environmental persistence but requires more frequent application. Not all botanicals are safe — rotenone is toxic to fish and linked to Parkinson's disease in mammals.
- Broad-Spectrum
- A pesticide that kills or affects a wide range of insect species, including both target pests and non-target beneficial insects. Pyrethrin, spinosad, and neem oil are all considered broad-spectrum organic insecticides. While broad-spectrum products are effective against multiple pest species simultaneously, they carry a higher risk of disrupting beneficial insect populations. IPM programs favor selective or targeted products when possible, reserving broad-spectrum treatments for severe infestations where multiple pest species are present.
- Bt Resistance
- The evolved ability of an insect population to survive exposure to Bacillus thuringiensis (Bt) toxins that would normally kill them. Resistance develops when Bt is used repeatedly without rotation, particularly in GM Bt crops where insects face constant selection pressure. Diamondback moth (Plutella xylostella) was the first field-documented case of Bt resistance. Resistance management strategies include rotating Bt with other control methods, using high-dose refuge strategies, and applying Bt formulations containing multiple Cry protein types.
C
- Contact Insecticide
- An insecticide that kills insects by direct physical contact rather than requiring ingestion. Contact insecticides must hit the pest or be present on a surface the pest walks across. Most organic insecticides are contact-based: insecticidal soap disrupts cell membranes on contact, horticultural oil smothers insects, and pyrethrin attacks the nervous system through the cuticle. The main limitation of contact insecticides is that they require thorough spray coverage — pests hiding on leaf undersides or inside curled leaves may be missed entirely.
- Cry Toxin (Crystal Protein)
- A protein produced by Bacillus thuringiensis bacteria that forms crystalline inclusions during sporulation. When ingested by a susceptible insect larva, Cry toxins dissolve in the alkaline gut environment, bind to specific receptors on gut wall cells, and create pores that rupture the cells. This causes the gut to leak, leading to septicemia and death within 24–72 hours. Over 70 different Cry toxin types have been identified, each with specificity for different insect groups. Cry1Ac targets Lepidoptera (caterpillars), Cry3Aa targets Coleoptera (beetles), and Cry4 targets Diptera (mosquitoes).
D
- Degree-Day
- A unit of accumulated heat used to predict insect development and time pesticide applications for maximum effectiveness. Degree-days are calculated by subtracting a base development temperature (below which the insect does not develop) from the average daily temperature. For example, codling moth has a base temperature of 50°F (10°C) — a day with an average of 70°F accumulates 20 degree-days. Codling moth first flight occurs around 100 degree-days, and first egg hatch around 250 degree-days after biofix. University extension services publish degree-day models for major pest species.
- Diatomaceous Earth (DE)
- A powder made from the fossilized shells of microscopic aquatic organisms called diatoms. Food-grade DE kills insects mechanically by absorbing the waxy lipid layer on their exoskeleton, causing death by desiccation within 24–48 hours. Effective against crawling insects including ants, cockroaches, slugs, fleas, and bed bugs. DE must remain dry to work — rain or heavy dew renders it ineffective until it dries again. Always use food-grade DE for pest control, never pool-grade (which is heat-treated and contains crystalline silica that is dangerous to lungs). OMRI-listed.
- Dormant Spray
- A pesticide application made to fruit trees and woody ornamentals during winter dormancy, before buds break in spring. Dormant sprays target overwintering pest eggs, larvae, and disease spores when they are most vulnerable and when beneficial insects are absent. Common dormant spray materials include horticultural oil (suffocates scale, mite eggs, and aphid eggs), lime sulfur (kills fungal spores and some insect eggs), and copper (primarily fungicidal). Timing is critical: apply after the coldest weather has passed but before buds show green tissue, typically when daytime temperatures reach 40–50°F for several consecutive days.
E
- Economic Threshold (ET)
- The pest population density at which control action should be taken to prevent the pest from reaching the economic injury level — the point where crop damage exceeds the cost of treatment. In home gardens, economic thresholds are less formal but the principle still applies: a few aphids on a tomato plant do not warrant spraying, but a rapidly growing colony causing visible leaf curl does. Key thresholds vary by crop and pest: for example, cabbage looper on broccoli typically warrants action at 0.3 larvae per plant, while aphids on lettuce may tolerate 10–20 per leaf before yield is affected.
- Emulsifiable Concentrate (EC)
- A liquid pesticide formulation that mixes with water to form a uniform emulsion for spraying. The active ingredient is dissolved in an oil-based solvent with emulsifiers that prevent the oil and water from separating. Many neem oil and pyrethrin products are sold as emulsifiable concentrates. EC formulations provide good coverage, are easy to mix, and require less agitation than wettable powders. However, the solvents in some EC formulations can cause phytotoxicity (plant burn) on sensitive species, especially at high temperatures or on young growth.
- Entomopathogenic Fungus
- A fungus that infects and kills insects. The two most commercially important species are Beauveria bassiana and Metarhizium anisopliae. Fungal spores land on an insect's cuticle, germinate, penetrate the exoskeleton, and colonize the body cavity, killing the host in 3–7 days. Infected insects often develop a characteristic white (Beauveria) or green (Metarhizium) fuzzy coating of sporulating fungus. These biocontrol agents work best in humid conditions (>60% RH) and are compatible with most other organic treatments. They can persist in the environment and provide ongoing suppression.
- Essential Oil (as insecticide)
- Concentrated volatile plant oils used as pesticides, primarily for repellent and contact-kill properties. The most effective insecticidal essential oils include rosemary oil, peppermint oil, clove oil (eugenol), thyme oil (thymol), and cedarwood oil. They work through multiple mechanisms: neurotoxic action on octopamine receptors, desiccation, and feeding deterrence. Essential oils break down very rapidly in the environment (often within hours), which means low persistence but also the need for frequent reapplication. Classified as minimum-risk pesticides under EPA 25(b) exemption, meaning they are exempt from federal registration requirements.
- EPA 25(b) Exemption
- A provision under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) that exempts certain minimum-risk pesticide products from EPA registration requirements. To qualify, a product must use only active ingredients from a specific EPA-approved list (which includes many essential oils like rosemary, peppermint, and clove) and only inert ingredients from a separate approved list. Products cannot make public health claims (like killing disease-carrying mosquitoes). The 25(b) exemption explains why so many essential-oil-based pest control products can be sold without EPA registration numbers on their labels.
F
- Formulation
- The physical form in which a pesticide active ingredient is prepared for use. Common organic insecticide formulations include: emulsifiable concentrate (EC — liquid mixed with water), wettable powder (WP — dry powder mixed with water), dust (D — applied dry), granular (G — scattered on soil), suspension concentrate (SC — pre-mixed liquid), and ready-to-use (RTU — no mixing needed). The formulation affects coverage, rainfastness, ease of application, and phytotoxicity risk. The same active ingredient in different formulations can perform very differently.
- Fumigant
- A pesticide that works in gaseous form to kill pests in enclosed or semi-enclosed spaces. In organic pest control, fumigation options are extremely limited. Sulfur dioxide and carbon dioxide are sometimes used in stored grain. For soil, solarization (covering moist soil with clear plastic for 4–6 weeks in summer) achieves a fumigation-like effect through sustained heat. True chemical fumigants like methyl bromide are prohibited in organic production. Essential oil vapors have some fumigant properties in enclosed greenhouse environments.
H
- Horticultural Oil
- A highly refined petroleum-based or plant-based oil used to control soft-bodied insects and mites by coating and suffocating them. Modern horticultural oils are classified by viscosity: dormant oils (heavier, applied to bare wood in winter) and summer/superior oils (lighter, safe on foliage during the growing season). They are effective against aphids, scale insects, mites, whiteflies, and insect eggs. Horticultural oils have very low toxicity to mammals and break down within days. The main risk is phytotoxicity — apply when temperatures are between 40–85°F, never on drought-stressed plants, and avoid sulfur-sensitive varieties within 30 days of a sulfur application.
I
- Insect Growth Regulator (IGR)
- A substance that disrupts normal insect development by mimicking or interfering with hormones that control molting and metamorphosis. IGRs prevent immature insects from reaching reproductive adulthood. The two main types are juvenile hormone analogs (which keep insects in the larval stage) and chitin synthesis inhibitors (which prevent the formation of new exoskeleton during molting). Azadirachtin from neem oil is a natural IGR. Synthetic IGRs like methoprene and pyriproxyfen are used in conventional pest control. IGRs are highly selective and generally safe for vertebrates and adult beneficial insects.
- Integrated Pest Management (IPM)
- A science-based decision-making framework for managing pests using the least-risk combination of biological, cultural, mechanical, and chemical controls. IPM follows four steps: (1) prevent pest problems through resistant varieties, crop rotation, and sanitation; (2) monitor pest populations through scouting, traps, and degree-day tracking; (3) establish action thresholds — only treat when pest levels justify it; (4) select the least-disruptive control method that will be effective. IPM is not zero-pesticide farming, but it reduces pesticide use by 50–70% compared to calendar-based spraying by treating only when necessary with targeted products.
- Inert Ingredient
- Any ingredient in a pesticide formulation that is not the active ingredient. Despite the name, inert ingredients are not necessarily harmless — they include solvents, carriers, emulsifiers, spreaders, and preservatives that can affect human health and the environment. EPA does not require inert ingredients to be listed by name on pesticide labels, only by total percentage. In organic production, OMRI and NOP standards restrict which inert ingredients are allowed. The term "other ingredients" is increasingly used instead of "inert" to avoid implying safety.
- Insecticidal Soap
- A potassium-salt-of-fatty-acids solution that kills soft-bodied insects on contact by disrupting their cell membranes and removing their protective waxy coating. Effective against aphids, whiteflies, mealybugs, spider mites, and thrips. Insecticidal soap must contact the pest directly — it has zero residual activity once dry. Commercially formulated insecticidal soaps (like Safer Brand) are specifically designed to minimize plant damage. Household dish soap is NOT the same: dish detergents contain surfactants and additives that strip plant cuticle wax, causing leaf burn and long-term stress. OMRI-listed.
K
- Kaolin Clay (Surround)
- A fine white mineral clay (aluminum silicate) sprayed on plants as a particle film that creates a physical barrier deterring insect feeding and egg-laying. The clay coating irritates insects on contact and makes the plant surface unrecognizable as a food source. Effective against a wide range of pests including apple maggot, codling moth, Japanese beetle, leafhoppers, thrips, and psylla. Kaolin does not kill insects — it is a repellent/barrier. It must be reapplied after heavy rain. The white residue washes off harvested produce. Surround WP is the primary commercial kaolin product for agriculture. OMRI-listed.
L
- LD50 (Lethal Dose 50)
- The dose of a substance required to kill 50% of a test population, expressed in milligrams of substance per kilogram of body weight (mg/kg). LD50 is the standard measure of acute toxicity — a lower LD50 means higher toxicity. For reference: caffeine has an oral LD50 of about 192 mg/kg in rats, pyrethrin is 1,200 mg/kg (low toxicity to mammals), and azadirachtin is >5,000 mg/kg (very low toxicity). LD50 values have significant limitations: they measure only acute single-dose toxicity, not chronic exposure, sublethal effects, or environmental persistence.
M
- Microbial Insecticide
- An insecticide whose active ingredient is a living microorganism — bacterium, fungus, virus, or protozoan — or its byproducts. Major examples include Bacillus thuringiensis (Bt), Beauveria bassiana, Metarhizium anisopliae, spinosad (from Saccharopolyspora spinosa), and codling moth granulovirus (CpGV). Microbial insecticides are generally highly selective, targeting specific pest groups while sparing beneficials. They are slower-acting than chemical insecticides (1–7 days) but often provide longer-lasting control through environmental persistence and secondary cycling in pest populations.
- Minimum-Risk Pesticide
- A pesticide product exempt from EPA registration under FIFRA Section 25(b) because it uses only active ingredients from a specific EPA-approved list of low-risk substances and only approved inert ingredients. The active ingredient list includes many essential oils (cedar, cinnamon, citronella, clove, garlic, peppermint, rosemary, thyme), corn gluten meal, dried blood, and white pepper, among others. Minimum-risk products may still require state registration in some states. The exemption does not mean the product is proven effective — only that EPA considers the ingredients low-risk enough to not require federal registration.
- Mode of Action (MOA)
- The specific biochemical mechanism by which a pesticide kills or disrupts a pest. Understanding mode of action is critical for resistance management — rotating between different MOA groups prevents pests from developing resistance. Major organic insecticide modes of action include: nerve and muscle disruption (pyrethrin, spinosad), gut toxins (Bt Cry proteins), growth regulation (azadirachtin), suffocation/desiccation (oils, soaps, DE), microbial infection (Beauveria, Metarhizium), and feeding deterrence (neem, kaolin). The Insecticide Resistance Action Committee (IRAC) classifies all insecticides by MOA group number.
- Monitoring (Pest Scouting)
- The systematic observation and recording of pest populations and damage levels to make informed management decisions. Monitoring methods include visual inspection, sticky traps (yellow for whiteflies and fungus gnats, blue for thrips), pheromone traps (species-specific lures for moths like codling moth), sweep nets, beat sheets, and soil sampling. Effective monitoring answers three questions: what pest is present, how many are there, and is the population growing or declining? IPM programs typically require weekly monitoring during the growing season. Records should include date, location, pest species, count, and plant growth stage.
N
- Neem Oil
- An oil pressed from the seeds of the neem tree (Azadirachta indica) containing the active compound azadirachtin and over 70 other limonoid compounds. Neem oil works through multiple mechanisms: antifeedant (insects stop eating), insect growth regulation (disrupts molting), repellent, and oviposition deterrent (discourages egg-laying). Effective against a broad spectrum of pests including aphids, whiteflies, mites, thrips, caterpillars, and beetles. Cold-pressed neem oil retains more azadirachtin (1,500–3,000 ppm) than clarified hydrophobic extract (which has azadirachtin removed). Apply in early morning or evening to avoid sun degradation and bee exposure. OMRI-listed.
- National Organic Program (NOP)
- The USDA regulatory program that develops and enforces standards for organically produced agricultural products in the United States. The NOP maintains the National List of Allowed and Prohibited Substances, which specifies which synthetic materials may be used and which natural materials are prohibited in organic production. For pest control, the NOP allows most biological and botanical insecticides, minerals like sulfur and kaolin, and approved synthetic materials like pheromone traps. Certified organic operations must document all pest management inputs and have them approved by their certifying agent.
O
- OMRI (Organic Materials Review Institute)
- An independent nonprofit organization that reviews and certifies products for compliance with USDA National Organic Program (NOP) standards. An OMRI-listed product has been verified to contain only ingredients allowed under organic production rules. OMRI listing is voluntary — a product can be NOP-compliant without being OMRI-listed, but the OMRI seal provides a quick verification for growers and consumers. OMRI reviews both active and inert ingredients. The OMRI Products List is searchable online and updated continuously. Note that OMRI listing means the product is allowed in organic production, not that it is safe or effective.
P
- Parasitoid
- An organism that develops in or on a host insect, eventually killing it — distinct from a parasite, which typically does not kill its host. Parasitoid wasps are the largest and most important group in biological pest control. Examples include Trichogramma wasps (lay eggs inside pest moth eggs), Aphidius wasps (parasitize aphids, leaving characteristic "mummies"), Encarsia formosa (parasitizes greenhouse whitefly), and tachinid flies (parasitize caterpillars and beetles). A single female Trichogramma wasp can parasitize up to 200 pest eggs. Parasitoids are generally highly host-specific, making them ideal for targeted biocontrol.
- Pheromone Trap
- A monitoring or control device that uses synthetic versions of insect sex pheromones to attract and capture specific pest species. Most pheromone traps use a sticky liner or funnel design. In IPM, pheromone traps serve two primary functions: monitoring (detecting pest presence and timing emergence for optimal treatment) and mass trapping/mating disruption (reducing pest populations by removing males or confusing mate-finding). Pheromone traps are species-specific, non-toxic, and do not affect beneficial insects. Common targets include codling moth, Oriental fruit moth, peachtree borer, and corn earworm. Traps should be deployed before expected flight periods.
- Phytotoxicity
- Plant injury or damage caused by a pesticide or other chemical substance. Phytotoxicity symptoms include leaf burn (necrosis), yellowing (chlorosis), stunted growth, flower or fruit drop, and leaf curl. Common causes in organic pest control include: applying horticultural oil at temperatures above 85°F, using dish soap instead of true insecticidal soap, spraying sulfur on sulfur-sensitive varieties (like certain cucurbits), applying neem oil in direct sunlight, and using excessive concentrations. Always test any new spray on a small area and wait 48 hours before full application. Young, stressed, or newly transplanted plants are most susceptible.
- Pollinator
- Any animal that transfers pollen between flowers, enabling plant reproduction. Key pollinators include honeybees, native bees (bumblebees, mason bees, leafcutter bees), butterflies, moths, hoverflies, and some beetles. Protecting pollinators is a critical consideration in organic pest management. Best practices include: never spray open flowers, apply pesticides in early morning or late evening when bees are less active, choose selective products over broad-spectrum when possible, maintain untreated flowering habitat near treated areas, and avoid neonicotinoid-contaminated transplants. Spinosad and pyrethrin are both toxic to bees on wet contact but safe once dry.
- Pyrethrin
- A natural insecticide extracted from the flowers of Chrysanthemum cinerariaefolium (now classified as Tanacetum cinerariifolium). Pyrethrins are a mixture of six related compounds (pyrethrin I & II, cinerin I & II, jasmolin I & II) that attack the insect nervous system by keeping sodium channels open, causing rapid knockdown and paralysis. Pyrethrins degrade within 12–24 hours in sunlight, giving them very low environmental persistence. They are broad-spectrum and toxic to bees on contact (but safe once dry), fish, and aquatic invertebrates. Pyrethrin is distinct from pyrethroids, which are synthetic analogs with much longer persistence. OMRI-listed.
- Pyrethroid
- A synthetic chemical insecticide modeled after natural pyrethrin but engineered for greater stability and longer persistence in the environment. Common pyrethroids include permethrin, bifenthrin, cypermethrin, and lambda-cyhalothrin. Pyrethroids share pyrethrin's sodium-channel mode of action but persist for days to weeks instead of hours. Pyrethroids are NOT allowed in organic production and are NOT the same as pyrethrin. This distinction is important because product labels can be confusing — any product containing a pyrethroid is synthetic and not OMRI-eligible. Pyrethroids are highly toxic to aquatic organisms and beneficial insects.
R
- Repellent
- A substance that deters pests from approaching or remaining on treated surfaces without necessarily killing them. In organic pest control, repellents include garlic sprays, hot pepper wax, essential oils (peppermint, cedarwood, citronella), kaolin clay particle films, and neem oil. Repellents work best as preventive treatments applied before pest arrival. They are generally less effective than contact insecticides for active infestations but have significant advantages: they are very safe for beneficial insects, have minimal environmental impact, and can be reapplied frequently without resistance concerns.
- Resistance Management
- Strategies to prevent or delay pest populations from developing genetic resistance to pesticides. The core principle is rotation: alternate between products with different modes of action (IRAC groups) so that resistant individuals selected by one product are killed by the next. Additional strategies include using the full labeled rate (sub-lethal doses accelerate resistance), incorporating non-chemical controls (cultural, biological, mechanical), applying products only when monitoring indicates treatment is needed, and using mixtures of different MOA products when available. Even organic insecticides can lose effectiveness through resistance — spinosad resistance has been documented in thrips and diamondback moth.
- Residual Activity
- The length of time a pesticide remains active and effective after application. Most organic insecticides have short residual activity: pyrethrin breaks down in 12–24 hours, insecticidal soap has zero residual once dry, and neem oil degrades in 1–3 days of sunlight exposure. Spinosad has moderate residual activity of 7–14 days. Bt spores can persist for several days on protected leaf surfaces. Short residual is generally beneficial in organic systems because it minimizes impact on beneficial insects that arrive after application, but it requires more frequent treatment and better spray timing.
S
- Selective Insecticide
- A pesticide that targets specific pest groups while leaving most non-target species unharmed. Bt kurstaki is highly selective — it kills only caterpillars that ingest it. Milky spore (Paenibacillus popilliae) targets only Japanese beetle grubs. Parasitic nematodes (Steinernema, Heterorhabditis) target soil-dwelling larvae. Selective insecticides are preferred in IPM programs because they preserve beneficial insect populations that provide natural pest control. The trade-off is that selective products may not work on mixed-pest infestations, requiring multiple products or strategies to address all pest species present.
- Signal Word
- A required word on pesticide labels that indicates the product's acute toxicity level to humans. The three signal words are: DANGER (highly toxic — oral LD50 of 0–50 mg/kg), WARNING (moderately toxic — LD50 of 50–500 mg/kg), and CAUTION (slightly toxic — LD50 of 500–5,000 mg/kg). Products with LD50 above 5,000 mg/kg may carry no signal word. Most organic insecticides carry CAUTION or no signal word. Products exempt under EPA 25(b) are not required to display signal words. The signal word applies to the formulated product, not just the active ingredient — so the same active ingredient in different formulations may carry different signal words.
- Solarization (Soil Solarization)
- A non-chemical soil treatment method that uses clear plastic sheeting to trap solar radiation and heat the top 6–12 inches of soil to temperatures lethal to soil-dwelling pests, weed seeds, and pathogens. Effective solarization requires 4–6 weeks of treatment during the hottest months, moist soil (which conducts heat better), and clear (not black) plastic. Soil temperatures under the plastic can reach 140°F (60°C) at the surface and 100°F (38°C) at 18 inches deep. Solarization is most effective in sunny, hot climates (USDA zones 7+) and kills nematodes, many soilborne fungi, weed seeds, and soil-dwelling insect larvae.
- Spinosad
- A naturally derived insecticide produced by fermentation of the soil bacterium Saccharopolyspora spinosa. Spinosad contains two active compounds (spinosyn A and spinosyn D) that disrupt insect nervous systems through a unique dual mode of action — activating nicotinic acetylcholine receptors and potentiating GABA receptor function. This makes it effective against pests already resistant to other insecticide classes. Highly effective against thrips, caterpillars, leafminers, fire ants, fruit flies, and Colorado potato beetle. Residual activity of 7–14 days. Toxic to bees on wet contact but safe once dry (3 hours). One of the most effective organic insecticides available. OMRI-listed.
- Spray Coverage
- The extent to which a pesticide spray reaches all target surfaces on a plant, particularly leaf undersides, stem crevices, and growing points where pests hide. Spray coverage is the single most common reason organic insecticides fail — most contact-kill products only work if they physically hit the pest. Improving coverage requires: proper spray equipment (fine mist nozzles, not coarse streams), adequate spray volume (wet both leaf surfaces to the point of drip), adding an approved surfactant/adjuvant, spraying from multiple angles, and treating in calm conditions. Coverage is more critical for contact insecticides (soap, oil, pyrethrin) than for systemic or ingestion-based products (Bt).
- Suffocation (Smothering)
- A physical mode of insect kill where oils, soaps, or other materials coat and block the spiracles (breathing pores) through which insects exchange gases. Horticultural oil and insecticidal soap both work partly through suffocation. This mechanism is effective because insects cannot develop genetic resistance to physical blockage — the same way humans cannot evolve resistance to drowning. Suffocation-based products require thorough spray coverage to coat the entire insect body. They are most effective against sessile or slow-moving pests (scale, mealybugs, mites) and eggs.
- Surfactant
- A substance that reduces the surface tension of water, allowing spray solutions to spread more evenly across waxy leaf surfaces and insect cuticles instead of beading up. Surfactants are the most common type of adjuvant. In organic systems, approved surfactants include yucca extract (Therm X-70), silicone-based spreaders (like Sil-Matrix), and plant-oil-based products. Insecticidal soap itself is a surfactant. Dish detergent also contains surfactants but includes additional chemicals (degreasers, fragrances, antibacterials) that damage plant tissue — this is why insecticidal soap and dish soap are not interchangeable.
- Systemic Insecticide
- An insecticide that is absorbed by the plant and distributed through its vascular tissue, killing insects that feed on any part of the treated plant. True systemics are rare in organic pest control. Neem oil has limited systemic activity when applied as a soil drench — azadirachtin is taken up by roots and distributed through xylem, providing 2–3 weeks of protection against sucking and chewing insects. Most organic insecticides (pyrethrin, soap, oil, Bt) are NOT systemic. The systemic neonicotinoids (imidacloprid, clothianidin, thiamethoxam) are synthetic, not organic, and are implicated in pollinator decline.
T
- Translaminar
- A property of certain pesticides that allows them to penetrate through the leaf surface and form a reservoir within the leaf tissue, killing pests feeding on the opposite side. Translaminar activity is a middle ground between contact-only and fully systemic — the active ingredient moves through the leaf but not through the plant's vascular system to other leaves. Spinosad and abamectin both exhibit translaminar activity. This property is valuable because it means spray coverage of only the upper leaf surface can still control pests feeding on the underside, though direct coverage on both surfaces remains more effective.
- Trap Crop
- A plant species grown specifically to attract pest insects away from the main crop, concentrating them where they can be managed more easily. Trap cropping is one of the most evidence-based companion planting strategies. Effective examples include: Blue Hubbard squash to draw squash bugs and cucumber beetles away from summer squash, alyssum borders to attract hoverflies (whose larvae eat aphids), sunflowers to lure stink bugs away from tomatoes, and nasturtiums to attract aphids away from brassicas. Trap crops work best when the trap plant is significantly more attractive to the pest than the main crop and when concentrated pests on the trap are managed (removed, sprayed, or destroyed) before they reproduce and spread.