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Entomology 101, Pest Management
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Pest management, Topics, Insects as Pests, Effects of Insecticides, Integrated Pest Management, Chemical Control, Biological Control, Host-Plant Resistance to Insects, Physical Control, Cultural Control, Pheromones and Attractants, Genetic Manipulation of Pests
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Pest management, Become ‘pests’ when they interfere with welfare, aesthetics, or profits, Defined from a purely anthropocentric point of view, Pest can be a normal insect in the wrong place or numbers, Main pests are of crops and health
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Insects as pests, Assessment of pest status, Injury vs. damage, Most plants tolerate injury without loss of vigor, Level of injury for fruits is much lower (due to blemishes), Control becomes economic when:, Financial loss outweighs cost of control, Economic injury level (EIL): , , , EIL = C / VDK, , , C = cost of control measure, V = value in market per unit, D = yield loss per number of insects, K = reduction of pest numbers by control measure
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Insects as pests, Assessment of pest status, EIL will not be the same in all (or even similar) conditions - Miridae, Varies based on many conditions, Economic threshold (ET): , Different level than EIL and is predictive
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Insects as pests, Assessment of pest status, Pests can be: non-economic, occasional, perennial, or severe / key
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Insects as pests, Assessment of pest status, EIL does not consider external factors such as:, Natural enemies, Insecticide resistance, Adjacent control areas, Developed mostly as a means for more sensible pesticide use, EILs largely relevant only to agriculture, Limited when multiple pests are present
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Insects as pests, Why insects become pests, Insects become pests for many reasons:, Harmless insects are introduced to areas outside their native range, Previously harmless insects become vectors of pathogens, Move from feeding on native plants to introduced ones, Monocultural ecosystems create dense aggregations of predictable resources, Cultivation methods lead to increase in pest status and numbers, Continuous cultivation without a fallow period – broccoli, potatos, herbs, etc, Prolonged use of insecticides
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Effects of insecticides, Many insecticides developed during the 1950’s and 1960’s, , They are still the main tactic used today, , Undesirable effects of insecticides include:, Selection for genetically resistant insects, Collateral damage of non-pests, Pest resurgence, As a result of resistance and elimination of predators, Natural enemies often recover more slowly, Secondary pest outbreak, Economic contamination and biomagnification, Danger to human health , , Pest damage continues to increase despite heavy pesticide use
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Effects of insecticides, Insecticide resistance, Insecticide resistance: insects that are predisposed genetically to survive insecticide; develops over time, essentially a selection of a specific biotype, Tolerance: the ability to survive insecticide at some level; a natural tendency and not a result of selection pressure, CO potato beetle is resistant to nearly every chemical control , Multiple resistance: resistance to many different insecticides
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Effects of insecticides, Insecticide resistance, 4 mechanisms of insecticide resistance, Tobacco hornworm, Polyphagous insects are pre-adapted to evolve resistance, Problem of “kill-all” applications, This and other factors have led to other control methods
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Integrated pest management, IPM: a broad-based approach that integrates practices for economic control of pests, Aims to suppress pest populations below the economic injury level (EIL), Successful IPM requires knowledge of several key factors, Key concept: compatibility of pest-management tactic, Philosophy that may approach organic farming, Allows for safer pest control, Implementation of IPM has been slow, Reasons why the adoption rate of IPM is low
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Integrated pest management, IPM system is designed around 6 basic components: , Acceptable pest levels, Emphasis on control, not eradication, Annihilation can be costly and unsafe, Preventive cultural practices, Sanitation , Monitoring, Inspection and identification, Mechanical controls, Barriers, traps, picking, tillage, etc., Biological controls, Natural processes and materials, Responsible use, As required and at specific times
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Integrated pest management, Control measures of IPM include: insecticides, biological control, cultural control, plant resistance, genetic modification, pheromones, and growth regulation
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Chemical control, Despite the hazards, some use is unavoidable, Carefully timed doses reduce ecological damage, Chemicals enter the insect in 1 of 3 primary ways:, Cuticle, Contact poisons, Trachea, Inhalation poisons, Fumigants, Mouth, Stomach poisons, Some may act as all 3 simultaneously, Typically attack the nervous system
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Chemical control, Chemical insecticides, Alkaloids, Used since 1600’s, Natural, plant-derived; from nicotine in tobacco, Pyrethrins , Kills effectively on contact at low dosage, Low environmental persistence , Low mammalian toxicity, Nicotinoids / Neonicotinoids, Synthetic, modeled on natural nicotine, Carbamates , Organophosphates, Malathion, parathion, Organochlorines, DDT, Phenylpyrazoles, New class, Frontline, Maxforce
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Chemical control, Chemical insecticides, Formulation: components and proportions of additional substances that accompany an insecticide when prepared for application, , Modes of application:, Solutions or emulsions, Unwettable powders dispersed in water, Dusts or granules, Gaseous fumigants, , Can be formulated in different ways, , Concern about sublethal effects of pesticides on non-target organisms (honey bees), , Sublethal effects generally not considered
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Chemical control, Insect growth regulators, “IGR” – compound that inhibits an insect’s growth or development, Very efficient against specific stages of an insect pest, 2 types of IGRs, distinguished by their mode of action, Chemicals that disrupt the hormonal control of metamorphosis, Insect fails to reach adulthood, or is sterile and malformed, Useful when the adult is the pest, Chemicals that prevent the formation of chitin / cuticle, Insects die at or immediately after the molt, Useful for larval pests, Can result in severe pest outbreaks
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Biological control, Biological control: the establishment of natural enemies to control pests, Deliberate human intervention, Goal is reduction, not elimination, 3 types of biological control:, Classical biological control aka importation, Appropriate for when insect spread outside their natural range, Some great successes, many failures, Disastrous side effects (Hawai’I, Fiji), Neoclassical biological control: importation of non-native species to control native ones, High risk
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Biological control, 3 types of biological control:, Classical biological control aka importation, Vedalia beetle and cottony-cushion scale, Great success story of classical biological control , Scale was devastating the California citrus industry in the late 1800's, Vedalia ladybug and parasitoid fly were introduced, Controlled the scale population within just a few years, DeBach and Rosen suggested this “established the biological control method like a shot heard around the world”. (1991, Biological control by natural enemies, 2nd edition. Cambridge University Press)
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Biological control, 3 types of biological control (continued):, Augmentation: supplementation of existing natural enemies, Periodic release, Inoculation, Inundation, Can be helpful in reducing pesticide use, Conservation: protect or enhance activities of natural enemies, reducing pest effects, Preservation, Environmental manipulation – to improve conditions for predators and parasitoids, Failure in systematic studies can be very costly
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Biological control, Arthropod natural enemies, , Predators, Spiders, Diverse and efficient predators, Great impact on insect populations, Lack of feeding specificity, Many predators are polyphagous, Unsuitable for targeting particular pest species, , , Parasites and parasitoids, Most important biological control agents are wasps and flies, , , Complexities of food webs and complications
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Biological control, Microbial control, Includes: nematodes, fungi, bacteria, viruses, protists, Many are specific to a particular genus or family of insect, Entry mode, Strategies of control mimic those used with natural enemies, Nematodes, Desiccation restricts use to moist environments, Other environmental restrictions, Fungi, Most common disease organisms in insects, Ability to infect insect during any stage
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Biological control, Microbial control, , Bacteria, Bacillus thuringiensis, or Bt, Mode of action, Control is dependent on several factors, Increasingly used for control, Some resistance, Optimism that high levels of resistance is unlikely, Colorado potato beetle, , Viruses, Considered safe because of their restriction to insects, Mode of action and persistence in the environment
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Host-plant resistance to insects, Plant resistance: mechanisms by which plants resist insect attack, 3 types of plant resistance:, Antibiosis: plant negatively affects the biology of the insect, Factors include: toxins, growth inhibitors, low nutrients, trichomes, indigestibles , Antixenosis: plant deters insect feeding due to being a poor host, Factors include: repellents, deterrents, trichomes, waxes, thickness, toughness, Tolerance: plant is able to withstand or recover from insect damage, Involves only plant features and not interactions with insects
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Host-plant resistance to insects, Insect-resistant varieties of: corn, cotton, tobacco, tomato, potato, 2 methods of gene insertion into plants, Advantages over insecticides, Exacerbation of the situation by negatively affecting predators, Environmental risks from the use of transgenic plants:, Genes may transfer to other plants, Plant my become weedy itself, Non-target organisms may be affected
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Physical control, Non-chemical and non-biological methods, Indoors and outdoors, Fences, traps, trenches, packaging, swatters, Insect zappers, Should probably not be used, Statistical studies
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Cultural control, Crop pests, Crop rotation, tillage, burning of stubble, synchrony avoidance, plants for natural enemies, pest-free seeds, Intercropping, 4 hypotheses, Medical pests, Draining marshes, Container removal, Livestock pests, Removal of dung, Walk-throughs and dipping
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Pheromones and attractants, Sex pheromones can be used with great success, Other attractants such as food baits or oviposition sites can be used, 3 main uses for pheromones:, Monitoring, Mass trapping, Attraction-annihilation , Mating disruption, Pheromone dispensers create “noise”
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Genetic manipulation of pests, Screw-worm fly, Devastating pest, Eradication in US, Female mates only once, Swamping with infertile males, Sterile insect technique (SIT, SIRM), Gamma irradiation, , Tsetse fly, , Other successes around the world, , Lack of success can be due to many factors
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Questions?
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Permission
