Naranjo S E, Ellsworth P C, Chu C C, Henneberry T J
Western Cotton Research Laboratory, USDA-ARS, Phoenix, AZ 85040, USA.
J Econ Entomol. 2002 Aug;95(4):682-91. doi: 10.1603/0022-0493-95.4.682.
Studies were conducted in 1994 and 1995 to examine the effects of a range of action thresholds for managing Bemisia tabaci (Gennadius) Biotype B (= B. argentifolii Bellows & Perring) with insecticides in cotton on populations of arthropod predators in Imperial Valley, CA, and Maricopa, AZ. Application of insecticides significantly reduced population densities of spiders, Geocoris punctipes (Say), G. pallens (Stål), Orius tristicolor (White), Nabis alternatus Parshley, Zelus renardii Kolenati, Hippodamia convergens Guerin-Méneville, Spanogonicus albofasciatus (Reuter), Drapetis sp., and Chrysoperla carnea Stephens in one or both years and sites compared with untreated controls. Use of higher B. tabaci thresholds conserved some species and groups relative to lower thresholds. Stepwise regression analyses indicated that reductions in predator populations were generally influenced more strongly by the timing of the first insecticide application than by the total number of sprays necessary to maintain suppression of the pest below any given action threshold. A predation index, which weights the importance of each predator species based on their known frequency of predation on B. tabaci and another key pest, Pectinophora gossypiella (Saunders), was developed and analyzed. Patterns were similar to results based on changes in abundance alone, but the index generally revealed less severe effects of insecticides on overall predator function. The current action threshold for conventional insecticidal control of B. tabaci in Arizona and southern California is five adults per leaf. Results here suggest that predator conservation may be enhanced by raising the initial threshold to delay the first application or initially using more selective materials such as insect growth regulators.
1994年和1995年开展了多项研究，以考察在加利福尼亚州帝王谷和亚利桑那州马里科帕，使用杀虫剂防治棉花上的烟粉虱生物型B（ = 银叶粉虱）时，一系列防治阈值对节肢动物捕食性天敌种群的影响。与未处理的对照相比，施用杀虫剂在一年或两年以及两个地点均显著降低了蜘蛛、点脉姬蝽、苍白姬蝽、三色小花蝽、交替盲蝽、雷氏蛛缘蝽、多异瓢虫、白翅叶蝉、草蛉等捕食性天敌的种群密度。相对于较低的阈值，采用较高的烟粉虱阈值能保护一些物种和类群。逐步回归分析表明，捕食性天敌种群数量的减少通常受首次施用杀虫剂时间的影响比受为将害虫抑制在任何给定防治阈值以下所需喷雾总次数的影响更大。开发并分析了一个捕食指数，该指数根据每种捕食性天敌已知捕食烟粉虱和另一种主要害虫棉铃虫的频率来权衡其重要性。其模式与仅基于数量变化的结果相似，但该指数通常显示杀虫剂对整体捕食性天敌功能的影响较小。亚利桑那州和南加利福尼亚州对烟粉虱进行常规杀虫防治的当前防治阈值是每片叶5头成虫。此处的结果表明，提高初始阈值以推迟首次施药，或最初使用更具选择性的药剂（如昆虫生长调节剂），可能会增强对捕食性天敌的保护。
