Exploitation of interspecific signals to deter oviposition by spotted-wing drosophila

铃木果蝇（Drosophila suzukii）是一种世界性的水果害虫，俗称斑翅果蝇（SWD），近年来从东南亚蔓延开来，对许多国家的水果作物造成了危害。这种苍蝇最初是在英国英格兰南部被发现的（2012年），随后它的数量增加并向北扩散，造成的水果损失估计为每年2000万至3000万英镑。除了核果（尤其是樱桃）外，所有四种浆果作物（覆盆子、草莓、蓝莓和黑莓）都受到影响。SWD造成的威胁意味着许多种植者被迫使用更多的杀虫剂。这一战略不能长期持续：已经有旨在尽量减少新鲜农产品中杀虫剂残留和防止抗药性出现的限制措施。喷洒杀虫剂还损害了种植者控制其他害虫的管理规划，这些规划通常包括使用有益的天敌将害虫数量减少到可接受的水平。在这个为期三年的研究项目中，我们将利用果蝇和它的姐妹种之间强烈的自然种间相互作用，开发一种新的方法来控制这种害虫。该项目将确定新的化学产卵威慑剂，可在种植区域内使用，以防止SWD对水果的损害，作为IPM战略的新组成部分。这些种间产卵障碍的存在及其对SWD的影响已在我们最近的实验中得到证实。在黑腹扁蝽产卵的基质（水果或人工培养基）暴露后，SWD的产卵（产卵行为）受到强烈抑制。即使少量的黑腹夜蛾（5只雌性交配）对SWD也有强烈而持久的抑制作用，与未暴露的底物相比，暴露于黑腹夜蛾的底物上沉积的SWD卵减少了87%。这表明，SWD检测到黑腹田鼠释放的一种化学信号，这种物种之间的化学交流导致了这种害虫对产卵的强烈抑制。在这项研究计划中，我们将调查黑腹扁扁虫（成虫或卵）在哪个阶段释放化学信号，导致SWD减少产卵。我们将从黑腹果蝇（以及其他果蝇物种，如果这些物质被证明更有效的话）中提取活性化学物质，并将这些信号（没有黑腹果蝇个体存在）应用于产卵基质，以证明这种化学物质本身就能阻止SWD。我们将调查社署如何检测活性化学物质，并通过调查感觉器官缺失（手术切除）或不工作（由于基因改造）的苍蝇的反应，显示这是通过嗅觉（相对挥发性化学物质）还是味觉（非挥发性）。这将识别负责检测化学威慑的感觉器官（例如触角或口器）。我们还将记录这些感觉器官对分离出来的提取物成分的电反应（例如使用色谱技术）。结合其他分析化学技术，我们将识别活性化学信号的化学结构，以便在实验室中合成。对SWD的行为和电生理影响将首先在小规模的实验室研究中进行测试，以确认阻止产卵的作用，然后在覆盆子和草莓作物上进行实地研究。在与种植者和行业代表协商后，我们将设计新的有害生物管理方法，包括部署产卵威慑剂。因此，这项研究计划将导致发现关于昆虫信号的新的科学价值信息，并实施新的作物保护方法。

The worldwide invasive fruit pest, Drosophila suzukii, commonly known as spotted wing drosophila (SWD), has spread from Southeast Asia in recent years, causing damage to fruit crops in many countries. The fly was first detected in the UK in Southern England (2012) and its population has subsequently increased and spread north, causing loss of fruit estimated at £20-£30 million pa. All four berry crops are affected (raspberry, strawberry, blueberry and blackberry), in addition to stone fruit (especially cherries). The threat caused by SWD means that many growers are forced to apply increased numbers of applications of insecticides. This strategy is not sustainable for the long term: there are already restrictions aimed at minimizing insecticide residues in fresh produce and preventing the emergence of resistance. Spraying insecticides also compromises the management programmes that growers follow to control other pests, which often include using beneficial natural enemies to reduce pest populations to acceptable levels. In this three-year research project, we will exploit the strong natural interspecific interactions between SWD and its sister species within the Drosophila melanogaster species group to develop a novel approach to control of the pest. The project will identify new chemical oviposition deterrents that can be applied within the cropping area to deter fruit damage by SWD as a new component of IPM strategies.The existence of these interspecific oviposition deterrents and their effects on SWD have been demonstrated in our recent experiments. Egg-laying (oviposition behaviour) by SWD was very strongly inhibited following previous exposure of the substrate (fruit or artificial media) to egg-laying by D. melanogaster. Even low numbers of D. melanogaster (five mated females) had strong and persistent inhibitory effects on SWD, with 87% fewer SWD eggs deposited on the substrate that was previously exposed to D. melanogaster, compared with unexposed substrates. This suggests that SWD detect a chemical signal released by D. melanogaster and that this chemical communication between the species results in very strong inhibition of egg laying by the pest.In this research programme, we will investigate which stage of D. melanogaster (adults or eggs) releases the chemical signals that are responsible for reducing egg-laying by SWD. We will extract the active chemicals from D. melanogaster (and other Drosophila species if these prove to be more effective) and apply the signals (without D. melanogaster individuals present) to egg-laying substrates to demonstrate that the chemical alone is responsible for deterring SWD. We will investigate how SWD detect the active chemical and show whether this is via smell (of relatively volatile chemicals) or taste (non-volatile), by investigating responses of flies that have sense organs missing (removed surgically) or not working (due to genetic modification). This will identify the sense organs responsible for the detection of the chemical deterrent (e.g. the antennae or the mouthparts). We will also record electrical responses of these sense organs to components of extracts that have been separated out (e.g. using chromatography techniques). Combined with other analytical chemistry techniques, we will identify the chemical structure of the active chemical signal for synthesis in the laboratory. Behavioural and electrophysiological effects on SWD will be tested to confirm egg laying deterrent activity, initially, in small-scale lab studies and then in the field on raspberry and strawberry crops. In consultation with growers and representatives from industry, we will design new approaches to pest management that include deploying oviposition deterrents. This research programme will therefore lead to the discovery of new scientifically valuable information on insect signalling and the implementation of new approaches to crop protection.