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

世界范围内的入侵水果害虫铃木果蝇，俗称斑翅果蝇(SWD)，近年来从东南亚蔓延开来，对许多国家的果树造成危害。这种苍蝇最早是在英国南部英格兰发现的(2012年)，随后其数量增加并向北扩散，导致水果损失估计为2000万GB-3000万GB/a。除核果(特别是樱桃)外，所有四种浆果作物(覆盆子、草莓、蓝莓和黑莓)都受到影响。社署造成的威胁意味着许多种植者被迫使用更多的杀虫剂。从长远来看，这一战略是不可持续的：已经有旨在尽量减少新鲜农产品中的杀虫剂残留和防止出现抗药性的限制。喷洒杀虫剂还损害了种植者为控制其他害虫而遵循的管理方案，其中往往包括使用有益的天敌将害虫数量减少到可接受的水平。在这项为期三年的研究计划中，我们会利用社署与其在果蝇种群内的姊妹物种之间的天然相互作用，发展一种控制害虫的新方法。这项计划会找出新的化学产卵威慑剂，作为综合防治策略的一个新组成部分，可应用于种植区内，以防止社署对水果造成损害。我们最近的实验证明，这些种间产卵威慑剂的存在及其对社署的影响。SWD的产卵(产卵行为)在之前暴露于底物(水果或人工介质)后受到非常强烈的抑制。即使数量很少的黑腹果蝇(5只交配雌虫)也对SWD有强烈而持久的抑制作用，与未暴露的底物相比，在先前接触黑腹果蝇的底物上沉积的SWD卵减少了87%。这表明，SWD检测到黑腹潜蝇释放的化学信号，这种物种之间的化学交流导致了对害虫产卵的非常强烈的抑制。在本研究计划中，我们将调查黑腹潜蝇的哪个阶段(成虫或卵)释放的化学信号导致SWD减少产卵。我们将从黑腹果蝇(以及其他果蝇物种，如果这些被证明更有效)中提取活性化学物质，并将信号(没有黑腹果蝇个体存在)应用于产卵底物，以证明该化学物质本身就负责阻止SWD。我们将通过调查感官缺失(通过手术切除)或无法工作(由于基因改造)的苍蝇的反应，研究社署如何检测到活性化学物质，并展示这是通过气味(相对挥发性化学物质)还是味道(非挥发性)实现的。这将确定负责检测化学威慑的感官(例如，触角或口器)。我们还将记录这些感觉器官对已分离出的提取物成分的电反应(例如，使用层析技术)。结合其他分析化学技术，我们将鉴定活跃的化学信号的化学结构，以便在实验室进行合成。将首先在小规模的实验室研究中测试对SWD的行为和电生理效应，以确认产卵威慑活性，然后在树莓和草莓作物上进行田间试验。我们将与种植者和工业界代表协商，设计新的害虫管理方法，包括部署产卵威慑剂。因此，这一研究方案将导致发现有关昆虫信号的新的具有科学价值的信息，并采取新的作物保护方法。

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.