Department of Ecology, Swedish University of Agricultural Sciences, Box 7044, SE-75007 Uppsala, Sweden.
J Econ Entomol. 2011 Jun;104(3):782-91. doi: 10.1603/ec10444.
Intensive use of pesticides is common and increasing despite a growing and historically well documented awareness of the costs and hazards. The benefits from pesticides of increased yields from sufficient pest control may be outweighed by developed resistance in pests and killing of beneficial natural enemies. Other negative effects are human health problems and lower prices because of consumers' desire to buy organic products. Few studies have examined these trade-offs in the field. Here, we demonstrate that Nicaraguan cabbage (Brassica spp.) farmers may suffer economically by using insecticides as they get more damage by the main pest diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), at the same time as they spend economic resources on insecticides. Replicated similarly sized cabbage fields cultivated in a standardized manner were either treated with insecticides according common practice or not treated with insecticides over two seasons. Fields treated with insecticides suffered, compared with nontreated fields, equal or, at least in some periods of the seasons, higher diamondback moth pest attacks. These fields also had increased leaf damage on the harvested cabbage heads. Weight and size of the heads were not affected. The farmers received the same price on the local market irrespective of insecticide use. Rates of parasitized diamondback moth were consistently lower in the treated fields. Negative effects of using insecticides against diamondback moth were found for the density of parasitoids and generalist predatory wasps, and tended to affect spiders negatively. The observed increased leaf damages in insecticide-treated fields may be a combined consequence of insecticide resistance in the pest, and of lower predation and parasitization rates from naturally occurring predators that are suppressed by the insecticide applications. The results indicate biological control as a viable and economic alternative pest management strategy, something that may be particularly relevant for the production of cash crops in tropical countries where insecticide use is heavy and possibly increasing.
尽管人们越来越意识到使用农药的成本和危害，并且这种意识有着悠久的历史且记录完备，但农药的密集使用仍在不断增加。通过充分控制虫害来增加产量所带来的益处，可能会因害虫产生抗药性和有益的自然天敌被杀死而被抵消。其他负面影响包括人类健康问题和价格下降，因为消费者希望购买有机产品。很少有研究在实地考察这些权衡取舍。在这里，我们表明，尼加拉瓜白菜（芸薹属）种植者可能会因经济上的损失而遭受损失，因为他们在使用杀虫剂的同时，主要害虫小菜蛾（Plutella xylostella（L.））（鳞翅目：菜蛾科）对白菜造成的损害更大，而他们同时也在经济资源上投入了杀虫剂。两个季节的两个相似规模的经标准化种植的白菜田，要么按照常规做法用杀虫剂处理，要么不用杀虫剂处理。与未处理的田地相比，用杀虫剂处理的田地遭受了同等程度或至少在季节的某些时期遭受了更高水平的小菜蛾虫害。这些田地的收获白菜头部也出现了更多的叶片损伤。白菜头部的重量和大小没有受到影响。无论是否使用杀虫剂，农民在当地市场上获得的价格都是相同的。处理过的田地中寄生小菜蛾的比例始终较低。用杀虫剂防治小菜蛾对寄生蜂和捕食性黄蜂等捕食性天敌的密度产生了负面影响，并且往往对蜘蛛产生负面影响。在使用杀虫剂的田地中观察到的叶片损伤增加可能是害虫对杀虫剂产生抗药性的综合结果，也是由于自然发生的捕食者的捕食和寄生率降低所致，而这些捕食者是被杀虫剂的应用所抑制的。研究结果表明，生物防治是一种可行且经济的替代害虫管理策略，对于在杀虫剂使用量大且可能增加的热带国家生产经济作物而言，这可能尤其重要。
