Alternative insecticides

Alternative insecticides  Benefits: – – Less persistent in the environment Less toxic to nontarget organisms  More specific modes of action Botanical insecticides –  Examples include      Synergists may be beneficial Soaps and oils Microbial insecticides Growth regulators Pheromones Botanicals and Related Natural Products “Botanicals” are derived from plants Overview   Definition, general characteristics of botanical insecticides Older botanicals – Origins, modes of action, toxicity, and uses Origins, modes of action, toxicity, and uses    More recent botanicals – New investigations Criteria for success – – – – Assessing effectiveness Consistent and economical production Regulatory approval Scale of use Botanicals  Prepared from plants Crude dusts or powders (pyrethrum) – Extracts or resins (pyrethrins, neem seed oils) – Isolated, refined components (d-limonene, linalool) Always -- minimal alteration of naturally occurring compounds –  Strengths and weaknesses – – – – Rapid action Rapid degradation Low toxicity to mammals (in general, not always) Minimal technology required for preparation Older botanicals and their origins     Nicotine – Nicotiana spp. Pyrethrins – Chrysanthemum cinerariaefolium Rotenone – Derris, Lonchocarpus and other legumes Sabadilla – Schoenocaulon officinale (a tropical lily) – Similar veratrine alkaloids in white hellebore, Veratrum album   Ryania – Ryania speciosa Others – Soaps, horticultural oils, essential oils, diatomaceous earth Modes of action, toxicity, and uses Nicotine Pyrethrins Acetylcholine mimic Toxicity: Mod-High (dermal and oral) Greenhouse / Homoptera Animals, humans, organic crops Beetles in organic crops Squash bug Na+ / K- ion trans Toxicity: Low in axons Electron transfer in cellular respiration Toxicity: Moderate (implicated in Parkinson’s disease) Rotenone Sabadilla Nerve membrane Toxicity: Low (but function mucous membrane irritant) Calcium channel disruptors (axonic) Toxicity: Low Ryania Beetles, caterpillars in organic crops Regulatory and marketing status in the United States  Only pyrethrins are widely available with labels covering a range of crop, animal, indoor, and human uses More recent botanicals (and similar ingredients) and their origins      Linalool and d-limonene – citrus oil derivatives Neem – Azadirachta spp. and Melia spp. Garlic oils Hot pepper oils Microbials – Toxins from Bacillus thuringiensis and other soil micro-organisms (avermectins, spinosyns) Azadirachta windbreak. (E. Fernandez, http://www.css.cornell.edu/ ecf3/Web/new/AF/arid.html) Modes of action, toxicity, and uses Citrus derivatives Neem Garlic oil Hot pepper extracts Microbials Multiple Nerve cell stimulants Multiple actions, ecdysone agonist ? ? Low Very Low (medicinal uses) Low Low Low On pets, indoor plants Many crop pests Many labeled uses, limited positive data on effectiveness Many for Bt and other products Regulatory and marketing status in the United States     Limonene and linalool Neem Garlic oil Hot pepper extracts     Many labels Used primarily in organic production of high-value crops Homeowner products Efficacy is questionable Effectiveness of currently available botanicals  Older botanicals – Generally well understood based on field trials and small plot trials from 1920s through 1950s More unsupported label claims  More recent products – Future integration of botanical insecticides into pest management programs  Effectiveness – Need for funded studies of efficacy  Not always part of small company’s plans  Consistent and economical production – – Different standards for high-value versus low-value crops and settings Different standards for developed versus developing countries “Reduced risk” track in the U.S. Registration still required in nearly all instances  Regulatory approval – –  Appropriateness to scale and value of target crop Insecticidal soaps – – – – – – Salts of fatty acids Kill insects by disrupting membranes (including tracheal linings) Work only against those insects that are wetted by the spray ... no residual action Effective against aphids, whiteflies, mites, and other soft-bodied, not-too-mobile pests Best-known brand names are Safer’s and M-Pede Make your own? Generally ... NO !!! Oils … may be vegetable oils or highly refined petroleum oils     Dormant oils for fruit and landscape trees – Against overwintering aphid eggs, mite eggs, scales reduce virus transmission, may suppress powdery mildew Against mites, aphids, other soft-bodied pests Stylet oils – Summer oils – Coverage is essential (upper and lower leaf surfaces); oils kill by suffocating pests that are sprayed directly Absorbents & abrasives   Clays, diatomaceous earth, silica aerogels – disrupt the insect’s cuticle and kill by dehydration Kaolin ... “Surround” Elemental and naturally occurring chemicals   Sulfur – effective miticide (may cause plant injury)  Copper Arsenic Microbials      Bacteria Viruses Fungi Microsporidia (Protozoans) Nematodes Covered earlier in the semester with biological control Microbials … more or less  Spinosads … including SpinTor and Entrust by Dow – – – Derived from a soil actinomycete Effective against a range of insects, including corn earworm, Colorado potato beetle, the “worms” on cabbage and related cole crops, apple maggot, and (less so) codling moth At least a portion of the activity of the spinosyns results from their functioning as mimics of acetylcholine. Microbials … more or less    Avermectins From Streptomyces avermitilis, a Grampositive soil bacterium Block nerve transmission that is mediated by GABA ... more common in insects and mites than in other animals. These compounds are GABA "agonists" ... promoters. Commercially available as Ivomec, Agri-Mek, others. Avermectins See: http://home.comcast.net/~john.kimball1/BiologyPages/I /InsectHormones.html Insect growth regulators      Because they are enclosed in an exoskeleton, insects must "shed their skins", or molt, to grow larger. The molting process in immatures and the transformation from larva to pupa to adult is regulated by hormones. One is ecdysone (molting hormone) secreted by the prothoracic gland; it stimulates shedding of the cuticle. Another is juvenile hormone (JH). JH is secreted from the corpora allata; it suppresses adult characteristics. As growth during each stage triggers secretion of ecdysone, if juvenile hormone is present, the cuticle is shed and replaced, and the insect reaches its next juvenile stage. As the immature insect grows and eventually discontinues production of juvenile hormone, secretion of ecdysone in the absence of JH triggers pupation and subsequent development of adult form. Synthetic hormones that mimic JH and ecdysone have been developed for use as insecticides that disrupt insect development and cause death. Insect growth regulators   The insect cuticle is comprised in part of chitin (N-acetyl-Dglucosamine), a complex polymer that gives strength and flexibility to the insect exoskeleton. Compounds identified as chitin inhibitors also are considered to be insect growth regulators and have been developed as insecticides. Insect growth regulators    Compounds that interfere with the function of juvenile hormone Compounds that interfere with the function of ecdysone (molting hormone) Compounds that interfere with chitin formation Juvenile hormone mimics     methoprene hydroprene kinoprene pyriproxyfen Methoprene   Against Diptera and Siphonaptera, somewhat against Coleoptera, Lepidoptera, and Homoptera Altosid is used as a feed additive for control of fly larvae in cattle dung, also as a (larval) mosquito control agent (and in other uses) Hydroprene  Against cockroaches, indoors, under the trade name GenTrol Kinoprene  Against aphids, whiteflies, scales, and mealybugs, under the trade name Enstar See: http://www.alanwood.net/pesticides/kinoprene.html Pyriproxyfen  Against an eclectic range of flies (including mosquitoes and midges), beetles, scales, and whiteflies. Trade names include Esteem, Knack, and Nemesis. Chitin inhibitors      diflubenzuron (Dimilin) lufenuron (Program) (not widely used) buprofezin hexaflumuron (Sentricon termite control) novaluron (Rimon) novaluron Ecdysone agonists (= promoters)    tebufenozide (Confirm) methoxyfenozide (Intrepid) halofenozide (Mach 2, against cutworms in turf) methoxyfenozide Existing compounds target Lepidoptera Synergists  MGK 264  Block metabolism by mixed function oxidases and other detoxifying enzymes, thereby making the insecticide more effective Examples include piperonyl butoxide, sulfoxide, and MGK 264 Piperonyl butoxide Pheromones for direct control   Removal trapping Mating disruption – Sustained release dispensers, sprayable formulations, aerosol “puffers”