lecture20

lecture20 - Biological Control and Conservation Biological...

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Biological Control and Conservation July 29 1 Biological Control – the use of natural enemies to control pests Pest – an organism that interferes with human activities Chemical Control – pesticides Problems with pesticides: Problems with pesticides: ± Expensive ± Toxic to non-target organisms Silent Spring (1962) Rachel Carson ± Pesticide resistance ± Pest resurgence Classical Biological Control Theory and Practice ± In their native land, insects are held in check by natural enemies ± Species is introduced to a foreign land without its natural enemies and becomes a pest ± Go to the native land, find the natural enemies and introduce them to the foreign land where the species has become a pest ± Consistent with the HSS Hypothesis
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Biological Control and Conservation July 29 2 Biological Control of Cottony -Cushion Scale by Ladybird Beetles Cushion Scale by Ladybird Beetles ± 1872 – Cottony-cushion scales were first discovered in California. ± 1889 – Ladybird beetles from Australia were introduced to California ± 1887 – Citrus industry in California was threatened with destruction ± 1890 to 1950 – Cottony-cushion scales were rare ± 1950 to present – Cottony-cushion scales have become more abundant, possibly due to the wide-spread use of insecticides which kill ladybird beetles
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Biological Control and Conservation July 29 3 Biological Control of Floating Fern by Weevils Biological Control of Floating Fern by Weevils ± 1970-1982 – Floating fern was a major pest in Australia, forming dense mats that clogged waterways and killed most of the fauna ± 1940 to 1970 – Floating fern, native to South America, was
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lecture20 - Biological Control and Conservation Biological...

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