Importation of biological control agents is a government activity for the common good. Funds for such work are typically provided by governments, but may in some cases come from grower organizations representing particular crops in a region. Costs of projects are concentrated at the beginning of the work, as costs to search for and study new candidate natural enemies are high. Use of proven biological control agents in newly invaded loca tions as the pest spreads is cheaper, as much of the initial work will not have to be repeated and known natural enemies can quickly be introduced. Benefits of successful projects accrue indefinitely into the future and benefit to cost ratios of past projects have averaged 17:1, with some projects having much higher ratios, of 100 or even 200:1. In successful programs, control is permanent and does not require continued annual investments to sustain the bene fits, in contrast to other forms of pest control (e.g., pesticide applications). This makes the method particularly attrac tive for use to protect natural areas and to protect crops in countries with resource poor farmers. Biological control also promotes good environmental stewardship of farm lands in developed countries.

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