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Pesticides

Pesticides. PEST = any organism that interferes in some way with human welfare or activities. PESTICIDE = toxic chemicals used to reduce the size of and control the pest population. Grouped by their target organism Insecticide , Herbicide , Fungicide , Rodenticide

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Pesticides

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  1. Pesticides

  2. PEST = any organism that interferes in some way with human welfare or activities.

  3. PESTICIDE = toxic chemicals used to reduce the size of and control the pest population. • Grouped by their target organism Insecticide, Herbicide, Fungicide, Rodenticide • 85% of pesticides worldwide used for Agriculture.

  4. “Ideal Pesticides” • Narrow-Spectrum= kill only target organism. • Breaks down easily into safe materials • Does not move around in the environment. • “Non-Ideal Pesticides” • Broad-Spectrum= kill more than just the target. • Persistent or Can degrade into other cmpds that can be more dangerous • Move around in the environment.

  5. Pre-1940s (First-generation pesticides) • Inorganics (Minerals) • Contain lead, mercury, and arsenic • Very persistent & bioaccumulate • Organics (Botanicals) • Plant-derived • Break down readily • Post-1940s (Second-generation pesticides) • Synthetic Botanicals • Made by altering natural botanicals • Ex: dichlorodiphenyltrichloroethane (DDT)

  6. INSECTICIDES : Classified by chemical structure • Chlorinated Hydrocarbons = organic cmpd + Cl • Broad-spectrum, persistent • Most are banned (DDT, endosulfan, etc) • Rachel Carson: Silent Spring • Organophosphates = organic cmpd + P • more poisonous than most others • not persistent, so they’ve replaced most chlorinated hydrocarbons • Carbamates = broad-spectrum, derived from carbamic acid • Less toxic to mammals (Carbaryl, Aldicarb)

  7. HERBICIDES • Classified by how they act & what they kill • Selective Herbicides = kill only certain types of plants • Broad-leaf Herbicides • 2,4-D & 2,4,5-T common in 1940s • 2,4,5-T banned by EPA in 1979 due to possible harmful side effects realized after its use in the Vietnam War • Grass Herbicides • Nonselective Herbicides = kill all vegetation

  8. VIETNAM WAR & HERBICIDES • US used mixtures of herbicides to kill vegetation in S.Vietnam to expose hiding places & destroy crops planted by Vietcong: Agent White, Agent Blue, & Agent Orange • Negative environmental impacts: • Mangrove forests & hardwood forests destroyed • Harmed ecology & economy of S.Vietnam • Negative health impacts: • Agent Orange = 2,4-D & 2,4,5-T combined. • Created highly toxic Dioxins during creation • Birth defects, stillbirths, female reproductive disorders, soft-tissue cancers • Bioaccumulated in fish = very high levels in Vietnamese people

  9. Benefits and Problems with Pesticides • Benefit: 1:Disease control • Fleas, lice and mosquitoes carry disease • Malaria- mosquito born • 2.7 million people die each year • Few drugs available, so focus is on killing mosquitoes • DDT

  10. DISEASE CONTROL • Malaria: carried mostly by female mosquitoes • Worldwide: 300-500M people currently suffer, 2.7M die each year. • DDT has helped the malaria problem greatly. • Sri Lanka: went from 2M cases each year to almost zero with the use of DDT. • When spraying stopped, more than 1M cases per year within 4 years. • Restarted DDT spraying in 1968 • DDT still used in at least 20 tropical countries to control mosquitoes.

  11. Benefits and Problems with Pesticides • Benefit: 2: Crop Protection • Pests eat and destroy 1/3 of world’s crops • Farmers save $3 to $5 for every $1 they invest in pesticides

  12. Benefits and Problems with Pesticides • Problem:1: Evolution of Genetic Resistance • Pest populations are evolving resistance to pesticides (right) • 520 insect & mite species & 84 weed species currently resistant

  13. Benefits and Problems with Pesticides • Problem: 2:Imbalances the Ecosystem • Spraying to kill insects can affect birds, rabbits, etc. • Despite 33-fold increase in pesticides since the 1940s, crop loss has not really changed

  14. Ecosystem Imbalances • Pesticides affect species other than intended pests. • Beneficial insects, birds, and others are often killed. • Indirectly responsible for killing many natural enemies of the pests (may starve/migrate looking for food after pesticide use) • Kill natural enemies directly sometimes • eating prey who have pesticides in their bodies

  15. Benefits and Problems with Pesticides • Problem:3: Creation of New Pests • Infestation of red scale insects on lemons after DDT sprayed to control another pest

  16. Benefits and Problems with Pesticides • Problem:4: Persistence, Bioaccumulation, and Biological Magnification • Bioaccumulation • The buildup of a persistent pesticide or other toxic substance in an organisms body

  17. Biological magnification • Increased concentration of toxic chemicals in tissues of organisms at higher trophic levels

  18. Biomagnification

  19. Benefits and Problems with Pesticides • Problem:5: Mobility in the Environment • Do not stay where they are applied • Move through soil, water and air

  20. NONPOINT SOURCES Rural homes Cropland Urban streets Animal feedlot POINT SOURCES Suburban development Factory Wastewater treatment plant

  21. Risk of Pesticides to Human Health • Short-term Effects of Pesticides • Handling food with pesticide residue • Mild case: nausea, vomiting, headaches • Severe case: damage to nervous system,

  22. Long Term Effects • Can cause cancer (lymphoma, leukemia, brain/lung/testicle/breast) • Sterility possible. • Higher rates of miscarriage • Greater risk: children of ag.workers (birth defects/stunted limbs) • Immune system suppression • Potential link to Parkinson’s.

  23. Pesticide Label Information • Brand name • Ingredients • Formulation • Signal word – DANGER, WARNING, CAUTION • Directions for use • Hazards to humans, animals, and the environment • Personal Protective Equipment Requirements • First Aid • Registration number, manufacturer name/address • Net contents

  24. Pesticide Ingredients • The active ingredients are specified on the label. • This information can help you compare different pesticide products. • Inert ingredients are not identified.

  25. Signal words • DANGER pesticides are extremely dangerous • A very small amount of a DANGER-POISON pesticide will kill a human or pet • DANGER pesticides can cause severe eye/skin injury • WARNING – larger amounts will injure humans • CAUTION pesticides are the least dangerous but can still cause injury

  26. Statements of Practical Treatment • Hazards to humans • Hazards to domestic animals • Acute effects statement (happen within 24 hours) • Delayed or chronic effects statement (happen over time such as cancer) • Your risk hazard from pesticide depends on the toxicity of the pesticide and your exposure to it

  27. Hazard Statements • Hazards to Humans • Eye, skin, inhalation, ingestion, etc. • Environmental Hazards • Birds, bees, groundwater, etc. • Consider the hazards before you buy a pesticide.

  28. Alternatives to Pesticides 1: Cultivation Methods • Interplanting = alternating rows of different plants • Strip Cutting = harvest one crop at a time, leaving habitat for natural predators of the pests. • Planting around marginsto keep habitat for natural predators. • Proper timing & crop rotation

  29. Alternatives to Pesticides 2: Genetic Controls • Create a pest-resistant crop by crossing pest-resistant plants w/ non-resistant. • Problems: fungi/bacteria/pathogens evolve quickly = must keep ahead! • 3: Genetically Modified (GM) Plants can be created quickly ! It could harm other parts of the environment ! • Many varieties are selective. Modify the gene = more general & more widely effective!

  30. Alternatives to Pesticides 4: Biological Controls • use naturally occurring disease organisms/ parasites/ predators to control pests. • >300 species have been introduced. • Careful that new control agents don’t become pests! (weevil/thistle) • Bt= soil bacterium that’s a great natural insecticide.

  31. Control Using Natural Enemies

  32. Alternatives to Pesticides 5: Quarantine • restrict import of exotic plants/animals that may harbor pests. • Effective, but not foolproof. • Ex: Mediterranean Fruit Flies (medflies) in California… it’s worked, but they keep coming back!

  33. Alternatives to Pesticides 6: Pheromones & Hormones • Pheromones = natural substances produced by animals to stimulate a response within their species. • Use to lure insects into traps! • Hormones = natural chemicals produced by insects to regulate their own growth/metamorphosis. • Given at wrong time: abnormal development & possible death.

  34. Alternatives to Pesticides 7: Reproductive Controls • Sterile Male Technique = sterilize males w/ radiation or chemicals. • Disadvantages: • Must be done continually to be effective - if discontinued, pest pop will rebound very quickly. • Expensive! $$$$$$

  35. 8: Irradiating Foods • Use ionizing radiation (gamma rays from cobalt 60) on harvested food to kill harmful microorganisms • First used in US: 1992 • Controversial, yet mostly safe. • Can cause free radicals (carcinogenic), but they normally occur produced by frying and boiling. • Don’t know the long-term effects yet.

  36. Integrated Pest Management (IPM) • Combine many methods of pest mgmt. • Pesticides are a last resort, and weak ones are used in low amts. • Important for Sustainable agriculture. • Used to MANAGE, not ERADICATE. • Determine when pest pop reaches an economic injury threshold when benefit of taking action exceeds cost. • Requires education on good strategies. • Overall, IPM use is low. Knowledge to use pesticides is less than to use IPM.

  37. Systems Approach- Integrated Pest Management (IPM) • IPM • Combination of pest control methods that keeps pest population low without economic loss • Conventional pesticides are used sparingly when other methods fail

  38. IPM Introduced Systems Approach- Integrated Pest Management (IPM) • Rice Production in Indonesia

  39. تعریف مقاومت توانايي بقاء يك حشره به غلظتي از سم كه قبلاً توسط آن غلظت كاملاً از بين ميرفت.

  40. مشکلات مقاومت به سموم در حشرات1ـ مقاومت به سموم در حشرات باعث بقای حشره در طبیعت و در نهایت ادامه خسارت اقتصادی و بهداشتی خواهد بود. 2ـ مقاومت در حشرات باعث افزایش غلظت سم برای کنترل بهتر حشرات شده در نتیجه از نظر اقتصادی، بار مالی بیشتری برای انسان داشته و آلودگی محیط زیست را نیز افزایش می‎دهد. 3ـ استفاده بیشتر از سموم باعث آلودگی محیط زیست شده و موجودات غیرهدف مثل حشرات مفید و موجوداتی که در سیر تکاملی جانوران و طبیعت نقش اساسی دارند را از بین می‎برد. 4ـ سموم استفاده شده، وارد چرخه تغذیه انسان و حیوانات شده و ناهنجاری های متفاوتی را باعث می‎گردد. 5ـ مقاومت به سموم، انسان را وادار به سرمایه‎گذاری در جهت کشف سموم جدید می‎نماید که این مسئله کاملاً مقرون به صرفه نمی‎باشد. 6ـ مقاومت به سموم در حشرات باعث بازپدیدی بیماری های مختلفی که توسط حشرات به انسان منتقل می‎شوند گردیده است. بطور مثال بازپدیدی و تداوم مالاریا یکی از نمونه‎های بارز مقاومت پشه آنوفل به سموم است.

  41. Pesticide Treadmill • Cost of applying pesticide increases • Because they must be applied more frequently or in larger doses • While their effectiveness decreases • Because of increased genetic resistance in pests

  42. مکانیسم های مقاومت به سموم در حشرات (Reduced penetration)1- کاهشنفوذسم (Metabolic resistance)2- مقاومت از طریق شکست سم توسط آنزیم های حشره (Target site insensitivity)تغییر در سیستم هدف در حشرات3- (Behavior change)4-تغییرات رفتاری (excretion)5- دفع سم

  43. فاکتورهائی که در مقاومت به سموم نقش دارند 1ـ فاکتورهای ژنتیکیمانند جهش , فراوانی ژنهای غالب مقاومت 2ـ فاکتورهای تولید مثلیمانند تعداد نسل در سال, اندازه جمعیت حشرات, تعداد جفت‎گیری, بکرزائی و غیره 3ـ فاکتورهای رفتاری اکولوژیکیمانند مهاجرت حشرات, فرار از حشره‎کش, اثر مواد طبیعی و آنزیمهای شکنندة سم, عادات درون خواری و برون‎خواری 4ـ فاکتورهای سم‎پاشیمثل سابقه استفاده از سموم, قسمتی از جمعیت که تحت تأثیر سم قرار می‎گیرند, غلظت حشره‎کش استفاده شده, خاصیت ابقائی سم, راه تماس, مرحله‎ای از رشد حشره که در تماس با سم قرار می‎گیرد. اثرات متقابل سموم با عوامل کنترل کننده محیطی, استفاده از مخلوط دو سم, الگوی سمپاشی, رهاسازی حشرات نر عقیم.

  44. مدیریت مقاومت 1ـ تغییر دادن غلظت حشره کش و دفعات سمپاشی 2ـ استفاده از سموم در مواقع ضروری و بصورت منطقه‎ای 3ـ استفاده از سموم در جائی که اپیدمی حاصل می‎شود 4ـ استفاده از سموم با خاصیت ابقائی کمتر 5ـ استفاده از سموم برای کنترل بخشی از سیکل زندگی حشره مثل لارو یا حشره کامل 6ـ استفاده از مخلوط دو سم 7ـ جایگزینی سموم 8ـ استفاده از سموم بصورت rotation 9ـ استفاده از فرمولاسیون های مناسب سموم 10ـ استفاده از سینرژیست‎ها 11ـ کشف سم جدید با مکانیسم عمل متفاوت 12ـ استفاده از روش های کنترل غیرشیمیایی

  45. فرومون ها Pheromones

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