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Controlling Insects!
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Insecticides Identify common insect pests and select an effective control method for each. Describe the six ways in which insects are killed by insecticides. List the names and characteristics of the three major groups of insecticides. Compare the six ways in which insecticides are applied. Explain the relationship between the life cycle of insects and timing of application.
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What is an insect? Insectsmall animal with three defined body regions and three pairs of legs! HEAD, THORAX, and ABDOMEN!
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6 Common Orders! Orthoptera- includes the grasshopper and locust
Hemiptera - includes the true bugs such as leaf hoppers and plant bugs Lepidoptera – moths and butterflies Homoptera- aphids Thysanoptera- thrips Coleoptera- which is the largest group of the insect orders, including beetles
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Insect grouping! How are insects grouped?
They are grouped by the way they feed on plants. So they are grouped by their mouth parts.
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Mouth Parts There are six different mouth parts Sponging
Rasping- sucking Siphoning Chewing-lapping Chewing Piercing- sucking
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How Insecticides Kill Chemicals must kill insects while doing little or no damage to the plant. Stomach poisonsWork against insects that eat parts of the plant. Sprayed or dusted on the plant As insect eats the plant, it is poisoned through the stomach. Insects that chew food (caterpillars, grasshoppers, beetles) are controlled by stomach poisons. Example--Rotenone
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How Insecticides Kill Contact Poisonskill insects when they are hit by or come in contact with the poison. Any type of insect can be controlled this way. Kill by upsetting the insect’s nervous system or breathing system. Example--malathion
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How Insecticides Kill Systemic poisonsenter the plant sap and move throughout the entire plant. When insect eats parts of plants or suck plant juice, chemical is swallowed. Effective with insects with chewing or sucking mouthparts. Effective with insects that hide under leaves or underground. Food crops—allow time for chemical to break down. Example--Orthene
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How Insecticides Kill Fumigantscontact poisons applied in gaseous form. Gases or fumes kill the insect after entering system through breathing pores. Insect must absorb the poison for this insecticide to be effective. Used to control soil-borne insects that damage roots. ExampleTAME
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How Insecticides Kill Repellantsdo not kill insects, but drive them away before they attack the plant. Examplealuminum foil (repels flying insects)
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How Insecticides Kill Attractants and Phermoneswork in the opposite way from repellants. They lure insects to their death. Page 171
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Chemical Makeup of Insecticides
Three groups! Inorganic Compounds Organic Compounds Synthetic Organic Compounds
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Inorganic Compounds Mineral origina mineral is used as the basis for the poison Usually work in the form of a stomach poison. Example—Sulfur
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Organic Compounds Derived from plants
Work in form of stomach or contact poisons Example—rotenone and pyrethrum
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Synthetic Organic Compounds
Recent origin (last years) Produced in the laboratory Many are also toxic to humans. Three Groups Chlorinated Hydrocarbons Organophosphates Carbamates
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Synthetic Organic Compounds
Chlorinated HydrocarbonsLong RESIDUAL Control (continue to kill long after application) ExampleDDT (not used in US)
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Synthetic Organic Compounds
OrganophosphatesContains chemicals most toxic to warm-blooded animals Absorbed rapidly through the skin Parathionone drop in the eye can kill a human being. ExampleMalathion (relatively safe)
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Synthetic Organic Compounds
Carbamatessafest insecticides on the market Break down rapidly (2-7 days) and leave no residue to contaminate the environment Do not build up in the bodies of warm-blooded animals Example—Sevin
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