Department of Entomology, Texas A&M University, College Station, Texas, United States of America.
PLoS One. 2013 May 3;8(5):e62620. doi: 10.1371/journal.pone.0062620. Print 2013.
Chemical suppression of arthropod herbivores is the most common approach to plant protection. Insecticides, however, can cause unintended, adverse consequences for non-target organisms. Previous studies focused on the effects of pesticides on target and non-target pests, predatory arthropods, and concomitant ecological disruptions. Little research, however, has focused on the direct effects of insecticides on plants. Here we demonstrate that applications of neonicotinoid insecticides, one of the most important insecticide classes worldwide, suppress expression of important plant defense genes, alter levels of phytohormones involved in plant defense, and decrease plant resistance to unsusceptible herbivores, spider mites Tetranychus urticae (Acari: Tetranychidae), in multiple, distantly related crop plants.
METHODOLOGY/PRINCIPAL FINDINGS: Using cotton (Gossypium hirsutum), corn (Zea mays) and tomato (Solanum lycopersicum) plants, we show that transcription of phenylalanine ammonia lyase, coenzyme A ligase, trypsin protease inhibitor and chitinase are suppressed and concentrations of the phytohormone OPDA and salicylic acid were altered by neonicotinoid insecticides. Consequently, the population growth of spider mites increased from 30% to over 100% on neonicotinoid-treated plants in the greenhouse and by nearly 200% in the field experiment.
CONCLUSIONS/SIGNIFICANCE: Our findings are important because applications of neonicotinoid insecticides have been associated with outbreaks of spider mites in several unrelated plant species. More importantly, this is the first study to document insecticide-mediated disruption of plant defenses and link it to increased population growth of a non-target herbivore. This study adds to growing evidence that bioactive agrochemicals can have unanticipated ecological effects and suggests that the direct effects of insecticides on plant defenses should be considered when the ecological costs of insecticides are evaluated.
抑制节肢动物取食是最常见的植物保护方法。然而，杀虫剂会对非靶标生物造成意想不到的负面影响。以前的研究主要集中在杀虫剂对靶标和非靶标害虫、捕食性节肢动物以及伴随而来的生态破坏的影响上。然而，很少有研究关注杀虫剂对植物的直接影响。在这里，我们证明了新烟碱类杀虫剂的应用——这是世界上最重要的杀虫剂类别之一——会抑制重要植物防御基因的表达，改变参与植物防御的植物激素水平，并降低植物对不易受侵害的食草动物（叶螨 Tetranychus urticae（蜱螨目：叶螨科））的抗性，在多种不同的作物植物中都是如此。
方法/主要发现：使用棉花（Gossypium hirsutum）、玉米（Zea mays）和番茄（Solanum lycopersicum）植物，我们表明新烟碱类杀虫剂会抑制苯丙氨酸解氨酶、辅酶 A 连接酶、胰蛋白酶蛋白酶抑制剂和几丁质酶的转录，并改变植物激素 OPDA 和水杨酸的浓度。因此，在温室中，叶螨的种群增长率从新烟碱类杀虫剂处理的植物上的 30%增加到 100%以上，在田间试验中增加了近 200%。
结论/意义：我们的发现很重要，因为新烟碱类杀虫剂的应用与几种无关植物物种中叶螨的爆发有关。更重要的是，这是第一项记录杀虫剂介导的植物防御破坏并将其与非靶标食草动物种群增长联系起来的研究。这项研究增加了越来越多的证据表明，生物活性农用化学品可能会产生意想不到的生态影响，并表明在评估杀虫剂的生态成本时，应考虑杀虫剂对植物防御的直接影响。
