Organic Gardening: Natural Insecticides


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Organic Gardening: Natural Insecticides

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Organic Gardening: Natural Insecticides

  1. 1. Organic Gardening–Natural IC O Insecticides M EX S TA N EW TE Guide H-150 N Y U T ® IV E RSI L.M. English Extension Entomologist Cooperative Extension Service • College of Agriculture and Home Economics This publication is scheduled to be updated and reissued 7/10.Despite our best efforts, nonchemical methods some- Sabadilla–Botanical insecticide. Sabadilla is obtainedtimes fail to prevent excessive insect damage in the from the seeds of a lily-like plant and acts as both a con-garden. At such times, the use of insecticides may be tact and stomach poison for insects. It is not particularlythe only alternative left to save the crop. When damage toxic to mammals, but it does cause irritation of thebecomes great enough to warrant emergency measures, eyes and respiratory tract. A mask should be worn whenorganic gardeners often will want to use natural insecti- working with this insecticide. This material deterioratescides and various homemade botanical sprays, instead of rapidly when exposed to light and can be used safely onsynthetic organic chemicals. food crops shortly before harvest. Generally Sabadilla is The insecticide used should have low toxicity to man used as a 5 to 20% dust or as a spray.and to other warm-blooded animals. Insecticides should Rotenone–Botanical insecticide. Rotenone is ex-be used only when needed and in strict accordance with tracted from the roots of derris plants in Asia and cubelabel directions. A good understanding of insecticides al- plants in South America. This general garden insecticidelows these materials to be used effectively without harm- is harmless to plants, highly toxic to fish and manying you or the environment. insects, moderately toxic to mammals, and leaves no The following information may help New Mexico gar- harmful residue on vegetable crops. It acts as both adeners select a natural insecticide for their specific needs: contact and stomach poison to insects. It is slow acting Pyrethrum–Botanical insecticide. This slightly toxic and, in the presence of sun and air, its effectiveness isinsecticide is derived from the flowers of a species of lost within a week after application. Wear a mask duringchrysanthemum imported mainly from Kenya and application because rotenone can irritate the respiratoryEcuador. The material causes rapid paralysis of most tract. Rotenone dusts and sprays have been used forinsects, but the insects usually recover unless the py- years to control aphids, certain beetles and caterpillarsrethrum is combined with a synergist or other poison. on plants, as well as fleas and lice on animals.Pyrethrum mixed with synergists such as piperonyl Neem–Botanical insecticide. Neem oil is an extractbutoxide or piperonyl cyclonene increases toxicity and from the Neem tree, Azadirachta indica (Meliaceae).produces longer, residual action, and is used extensively The neem tree is native to Southeast Asia and growsin space sprays, household sprays, crop sprays and dusts. in many countries throughout the world. It is a closeThis chemical is registered for use on most vegetables relative to the common Chinaberry tree. This treeand fruits at any time during the growing season. propagates readily from cuttings, stumps, tissue culture Nicotine–Botanical insecticide. Pure nicotine is a or seeds. It is widely used as a shade tree in many areastobacco extract highly toxic to warm-blooded animals. because it tolerates a wide range of conditions. TheThe insecticide usually is marketed as a 40% liquid neem tree has many medicinal uses. It has been used asconcentrate of nicotine sulfate, which is diluted in water an antiseptic and diuretic. It has been used to cure dis-and applied as a spray. Dusts can irritate the skin and are ease from diabetes to syphilis, and widely relied upon bynot normally available for garden use. Nicotine is used herbalists in its native habitat. The uses of the neem treeprimarily for piercing-sucking insects such as aphids, as a source of natural insecticides was discovered overwhiteflies, leafhoppers and thrips. Nicotine is more ef- 40 years ago.fective when applied during warm weather. It degrades The seeds of the neem tree contain the highestquickly, so it can be used on many food plants nearing concentration of azadirachtin and other biologicallyharvest. It is registered for use on a wide range of veg- active compounds. Because they contain the highestetable and fruit crops. concentration of these compounds, most experimental and commercial preparations of neem are seed extracts.To find more resources for your business, home or family, visit the College of Agriculture and Home Economics on theWorld Wide Web at
  2. 2. Some of the commercial insecticides registered by EPA • Apply insecticides to all plants surfaces so an insectare: Turplex, Neemguard, Margosan-0, Wellgro, Repe- anywhere on the plant will be exposed to a lethallin, Neemis, NeemazaL and Neemark. amount of the chemical. Do not apply insecticides These products generally are well known for their an- to wilted plants or during the hottest part of the day.tifeedant activity. The Lepidoptera (moths and butterflies Apply dusts only when the wind is calm and plantsand their larvae) are the most affected order of insects. are dry. Sprays should be applied when the wind isThese compounds also act as growth regulators, which no more than 5 to 10 miles per hour. Repeated treat-causes some larvae to remain in a permanent larval stage. ment may be necessary after a rain. Registered pesticide labels may vary, and you should • Apply insecticides only at recommended dosages.carefully study the label before use. Increased amounts can be dangerous, cause plant damage and leave harmful residues without improv-Other Pesticides ing insect control.Gardeners have been using soap to control insects since • The length of effective control with insecticides variesthe early 1800s. During the first half of the 19th century, widely. The longevity of toxic properties varies pri-whale oil soap and, more commonly, fish oil soaps were marily with the product, formulation, water, pH andan important part of insect control. Recent tests indicate environmental conditions. Temperature, humidity,Ivory Liquid dishwashing detergent, when diluted with wind and sunlight affect insecticides. The greater thewater to a 1 to 2% solution, provides the most consistent extremes, the sooner the insecticides are detoxified.control and is easy to mix. There are also soaps avail-able that are specifically formulated to control insects on • The time interval required by the Environmentalplants. Thorough coverage of the plant and repeated ap- Protection Agency between treating a crop and har-plications may be necessary to bring insect populations vesting that crop varies with the insecticide and theunder control. High rates of soaps and detergents may crop. This information is printed on the pesticidedamage some varieties of plants. The most effective soaps label to ensure that any residues will be within estab-have carbon chains of C-12 or C-18. Laurate (C-12) is lished tolerances at harvest time.the main component of most dishwashing liquids and • Always read and follow mixing and application in-various other products in common usage. The richest structions on the insecticide label for safe and effec-natural source of this is coconut oil. tive insect control. Organic gardeners have been using a spray mixture • Some synthetic organic materials are actually less tox-of onions, garlic and pepper to control insects for many ic and more efficient than some natural insecticides.years. Recent scientific research indicates using this mix- Because a material is a natural pesticide, it does notture has been erratic and, in many cases, ineffective for necessarily follow that it is not toxic to man or harm-insect control. Sprays of food-derived substances may ful to the environment if used improperly.have no or sporadic success. Spraying several times a week may help to bring In most situations it is helpful to use several controlinfestations under control. Expecting control with techniques to reduce insect pest populations to lowone application is unrealistic. enough levels that insecticides are not required, or are needed only sparingly. With reduced insecticide use,Safe Use of Pesticides biological control agents can become more effective, in-When it is necessary to use insecticides to protect the secticide costs will be saved, and you will have the satis-garden, use them wisely and safely. The following tips faction of knowing that few, if any, poisons were appliedwill help you make better use of insecticides. to edible crops.• Inspect the entire garden at least weekly to monitor insect numbers and activity. Pay particular atten- tion to underside of leaves where mites, whiteflies, The information given herein is supplied with the aphids and insect eggs occur. If treatments are applied understanding that no discrimination is intended when an infestation first starts, insect numbers can and no endorsement by the New Mexico Cooperative be maintained at lower levels much more easily, and Extension Service is implied. with smaller amounts of chemicals.New Mexico State University is an equal opportunity/affirmative action employer and educator. NMSU and the U.S. Departmentof Agriculture cooperating..Revised July 2005 Las Cruces, NM Guide H-150 • Page 2