ch18 - ENT 100 Fall 2009 1 Lecture 18: Pest Management...

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ENT 100 Fall 2009 1 Lecture 18: Pest Management Insects are considered pests when they conflict with our welfare, aesthetics and/or profits. However, the definition of an insect as a pest is clearly anthropocentric. There is no question that insects are our chief competitors for food and our chief assailants, feeding on us or animals associated with us and transmitting diseases to us. To measure the impact of insects in agricultural settings it is necessary to analyze each situation to determine the size of the pest population, the cost of controlling the insect and the economic losses that will occur if the insect is not controlled. This measurement is called determination of the Economic Injury Level . The Economic Injury Level is calculated using the cost of control, market value of the crop, estimated loss based on the number of insects, and the effectiveness of control measures. These calculations allow you to determine the Economic Threshold – the point where the cost of control is equal to the economic losses caused by pests. Why do insects become pests? 1. They are introduced into an area without regulatory agents, such as parasites, predators and pathogens. 2. The insect vectors a pathogen in a new situation. 3. A native insect shifts onto an introduced plant species. 4. They have simplified monocultural agroecosystems available for feeding 5. The overuse of insecticides, which leads to resistance and eliminates competitors, pathogens, predators and parasites. Pest species The pest status of an insect population depends on the abundance of individuals in an area, the kind of injury they do, and specific characteristics of the insect. General features that characterize insect pests include a high reproductive rate, short generation times, they tend to inhabit unstable habitats, and they are polyphagous, highly adaptable and are great dispersers. Economic threshold Equilibrium point Equilibrium point Parasite introduction Time Pest Nos.
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ENT 100 Fall 2009 2 Some examples of insect pests: House flies – one female housefly lays 100 eggs in her lifetime. The generation time of these flies depends on temperature; it could be as short as 2 weeks at temperatures over 80°F. They breed in rotting plant material and fecal material. Their eggs are simply dropped into a likely food source. Houseflies can reach enormous populations sizes in a few months. Evidence of this can be seen in Davis in August and September as houseflies develop huge populations in rotting tomatoes in the fields surrounding Davis. Tomato harvest begins in July. This means that houseflies can go through as many as ten generations before cold weather sets in. Aphids – one female aphid is capable of producing hundreds of offspring in her lifetime, and each of her offspring is capable of producing hundreds of offspring, within a couple of weeks. They are almost born pregnant. Aphids are largely parthenogenetic. A few aphid species specialize on a few plant species but these are the exceptions. Even these specialists can become
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This note was uploaded on 12/03/2009 for the course ENT 100 taught by Professor Kimsey,r during the Fall '08 term at UC Davis.

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ch18 - ENT 100 Fall 2009 1 Lecture 18: Pest Management...

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