Horticulture: Managing aphids and virus on lettuce - investigating components of an IPM strategy

莱切利被少数重要的害虫侵扰，其中大多数是蚜虫。其中一些蚜虫物种，特别是桃蚜和大戟长管蚜，已知会传播植物病毒，从而降低作物质量和产量。目前，主要通过应用杀虫剂处理来管理蚜虫及其传播的病毒。在英国，2019年有超过21，000公顷的生菜使用杀虫剂/杀线虫剂处理，其中超过55%的面积专门用于蚜虫。由于种植者可获得的有效活性成分的范围有限，害虫的室内控制对于种植者来说正变得越来越成问题，这也可能进一步受到杀虫剂抗性发生率的限制。很明显，种植者需要考虑替代方法来控制害虫，这些方法可以单独使用或与其他工具结合使用，作为综合害虫管理战略的一部分。一个基于决策的过程，涉及协调使用多种策略，以生态和经济合理的方式优化对所有类别害虫（昆虫，病原体，杂草，脊椎动物）的控制。'.使用多种策略是很重要的，因为仅仅依靠单一的工具对害虫施加高选择压力是不明智的，会导致控制失败。这方面的例子包括选择杀虫剂抗性和能够克服宿主植物抗性的害虫。可作为虫害综合防治战略的一部分采用的替代办法包括：寄主植物抗性、生物杀虫剂（可能是植物提取物、昆虫病原体或其他生物来源的物质）、生物控制剂（如捕食者和寄生虫）以及操纵蚜虫寄主植物寻找和寄主植物接受行为的技术，包括在系统中引入其他植物物种。额外的组分可以是非宿主植物/背景，其可以“干扰"宿主植物发现或”诱捕“植物，其将是比莴苣更优选的宿主并”吸引害虫“。在另一种方法中，甜alyssum（Lobularia maritima）在加州的有机莴苣作物中广泛种植，目的是吸引成年食蚜蝇进食。雌性食蚜蝇随后在莴苣上产卵，一旦孵化，幼虫就以蚜虫为食。 该项目的目的是评估IPM策略的几个组成部分的潜力，分别和一起管理莴苣作物上的蚜虫。这将包括潜在的非宿主伴侣植物/背景和“陷阱”植物，以防止蚜虫殖民莴苣作物植物，生物控制使用甜alyssum植物吸引天敌，特别是食蚜蝇，和生物农药，可能会降低莴苣作为宿主植物的适用性或减少蚜虫侵扰陷阱植物的数量。该项目将在实验室和Tygan House实验中重点关注桃蚜，但在田间实验中将考虑所有害虫蚜虫。行业合作伙伴将评估将更多物种纳入生菜种植系统的可行性和成本。如果这些方法中的任何一种看起来有希望，那么就必须进行更多的工作来开发它们并将其升级为商业用途。

Lettuce is infested by a small number of important pests, the majority of which are aphids. Some of these species of aphid, particularly Myzus persicae and Macrosiphum euphorbiae, are known to transmit plant viruses, which can reduce crop quality and yield. At present, both the aphids and the viruses they can transmit are managed mainly through the application of insecticide treatments. In the UK, over 21,000 hectares of lettuce were treated with insecticides/nematicides in 2019 and over 55% of this area was treated specifically for aphids. Insecticidal control of pest insects is becoming increasingly problematic for growers due to the limited range of effective active ingredients available to them, which may also be limited further by incidences of insecticide resistance. It is apparent that growers need to consider alternative approaches to pest control that might be used alone or in combination with other tools as part of an Integrated Pest Management strategy, which is '... a decision-based process involving coordinated use of multiple tactics for optimizing the control of all classes of pests (insects, pathogens, weeds, vertebrates) in an ecologically and economically sound manner.'. The use of multiple tactics is important, since it is unwise to rely solely on a single tool that applies high selection pressure to the pest, leading to a breakdown in control. Examples of this include selection for insecticide resistance and pests that are able to overcome host plant resistance. Alternative approaches that might be deployed as part of an IPM strategy include host plant resistance, biopesticides (which might be plant extracts, insect pathogens or other substances of biological origin), biological control agents (e.g. predators and parasitoids) and techniques for manipulating aphid host plant finding and host plant acceptance behaviour, including the introduction of additional plant species into the system. The additional components could be a non-host plant/background which can 'interfere' with host plant finding or a 'trap' plant, which would be a more preferred host than lettuce and 'draw the pests away'. In another approach, sweet alyssum (Lobularia maritima) is grown quite widely within crops of organic lettuce in California, the aim being to attract adult hoverflies to feed. The female hoverflies subsequently lay eggs on the lettuce and, once hatched, the larvae feed on aphids. The aim of this project is to assess the potential of several components of an IPM strategy to manage aphids on lettuce crops, separately and together. This will include potential non-host companion plants/backgrounds and 'trap' plants to prevent aphids from colonising lettuce crop plants, biological control using sweet alyssum plants to attract natural enemies, particularly hoverflies, and biopesticides that might decrease the suitability of lettuce as a host plant or reduce the numbers of aphids infesting trap plants. The project will focus on Myzus persicae in laboratory and Tygan House experiments but will take account of all pest aphids in field experiments. The industry partners will assess the feasibility and costs of incorporating additional species into the lettuce cropping system. If any of these approaches appear promising, then much more work will have to be undertaken to develop them and upscale them for commercial use.