Centre for Crop Systems Analysis, Wageningen University, Wageningen, The Netherlands.
Department of Science, Open University, Heerlen, The Netherlands.
Sci Rep. 2017 Feb 17;7:42210. doi: 10.1038/srep42210.
Immobilized preys are routinely used in agro-ecological exposure studies to quantify predation of pests under field conditions, but this method has not been validated. Our purpose was to determine the validity of using immobilized adults of the major rice pest Nilaparvata lugens, brown plant hopper (BPH), as sentinels. We used direct observation by video recording to determine the causal agents of removal of field exposed BPH sentinels with two experiments: 1) we recorded removal events of dead, immobilized BPH; and 2) we compared removal of (i) dead, immobilized BPH, (ii) live, immobilized BPH, and (iii) live, mobile BPH. Long-horned grasshoppers were responsible for most removals of dead, immobilized BPH, in both experiments. Predatory ground beetles removed most of the live, immobilized BPH, whereas frogs were the major predators of live, mobile BPH. Overall, we showed that removal of immobilized sentinel prey is not representative for predation of live, mobile prey, stressing the need for a critical assessment of commonly used sentinel methods. In addition, we found that frogs played the major role in predation of BPH in rice. As current strategies to enhance biocontrol of planthoppers in rice focus on arthropod natural enemies, this finding could have major implications.
固定的猎物通常用于农业生态暴露研究中，以量化田间条件下害虫的捕食情况，但这种方法尚未得到验证。我们的目的是确定使用固定的主要水稻害虫褐飞虱成虫作为哨兵的有效性。我们使用视频记录进行直接观察，通过两个实验来确定田间暴露的褐飞虱哨兵被移除的原因：1）我们记录了死亡、固定的褐飞虱的移除事件；2）我们比较了（i）死亡、固定的褐飞虱，（ii）存活、固定的褐飞虱和（iii）存活、移动的褐飞虱的移除情况。在这两个实验中，长角蚱蜢是导致大多数死亡、固定的褐飞虱被移除的主要原因。捕食性步甲甲虫移除了大多数存活、固定的褐飞虱，而青蛙则是移动的、存活的褐飞虱的主要捕食者。总的来说，我们表明，固定的哨兵猎物的移除不能代表对移动的、存活的猎物的捕食，这强调了对常用哨兵方法进行批判性评估的必要性。此外，我们发现青蛙在水稻褐飞虱的捕食中起着主要作用。由于目前增强水稻中对稻飞虱的生物防治的策略侧重于节肢动物的天敌，这一发现可能具有重大意义。
