In agroecosystems, the efficiency of biocontrol agents could be improved through the artificial selection of specific traits that would enhance their zoophagy level. The aim of this study was to evaluate the impact of artificially selected populations of the omnivorous predatory bug, Nabis americoferus, on the tarnished plant bug, Lygus lineolaris, in organic strawberry crops. Six populations of N. americoferus were selected according to their aggressiveness, three were composed of highly aggressive individuals, whereas the other lines contained docile individuals. The first hypothesis was that, since aggressive predators display a higher attack rate, aggressive lines would exhibit a higher pest control and a better crop protection than docile lines. The second hypothesis was that, when two biocontrol agents species are used conjointly, the presence of at least one docile population would generate a higher synergy between both species. N. americoferus populations were released in an experimental strawberry field, with or without a second intraguild predator, the Anthocorid, Orius insidiosus. Results support the first hypothesis that the aggressive lines generate a better pest control and a better strawberries crop protection than docile lines but only at low pest density. The second hypothesis is neither supported nor rejected since the combination of docile lines and O. insidiosus led to a better pest control at high pest density, but led to a reduced crop protection at low pest density. Our study shows that the artificial selection of aggressiveness has the potential to improve the effectiveness of biocontrol programs.

在农业生态系统中，可以通过人工选择特定性状来提高生物防治剂的效率，从而提高其食动物水平。本研究的目的是评估人工选择的杂食性掠食性昆虫Nabis americoferus种群对有机草莓作物中的黑盲蝽 ( Lygus lineolaris ) 的影响。根据美洲虎的攻击性，选择了六个种群，其中三个由高度攻击性的个体组成，而其他品系则包含温顺的个体。第一个假设是，由于攻击性捕食者表现出更高的攻击率，攻击性品系将比温顺品系表现出更高的害虫控制能力和更好的作物保护能力。第二个假设是，当两种生物防治剂物种联合使用时，至少一个温顺种群的存在将在两个物种之间产生更高的协同作用。N. americoferus种群被释放到实验草莓田中，有或没有第二个行会内捕食者 Anthocorid Orius insidiosus。结果支持第一个假设，即攻击性品系比温顺品系产生更好的害虫控制和更好的草莓作物保护，但仅在害虫密度较低的情况下。第二个假设既没有得到支持也没有被拒绝，因为温顺品系和O. insidiosus 的组合在高害虫密度下可以更好地控制害虫，但在低害虫密度下会导致作物保护减少。我们的研究表明，人为选择攻击性有可能提高生物防治计划的有效性。