Novel Semiochemical-Based Management of Fall Armyworm (FAW) in Brazil using Companion Crops

在巴西，玉米是一种重要的作物，是饮食中碳水化合物、维生素和矿物质的来源。巴西的许多小农场都是作为家庭企业经营的，为家庭提供生计，因此经济繁荣和生存可能完全取决于玉米收成的成功。不幸的是，许多害虫袭击玉米植株，造成严重的作物损失。虽然可以通过杀虫剂，甚至一些其他虫害管理工具（如影响虫害行为的信息素）来保护玉米免受虫害，但这些选择大多数（如果不是全部的话）对小农来说是负担不起的，而且没有其他可用的管理选择。开发保护重要玉米作物的新策略是至关重要的。害虫利用它们的嗅觉来探测和定位适合取食和产卵的寄主植物。寄主植物的气味由吸引人的挥发性化合物组成，但是当害虫开始破坏寄主植物时，当植物保护自己时，气味就会发生变化，它们对害虫就没有吸引力了。这一现象的进一步发展是，害虫的天敌“调谐”到植物被害虫破坏时产生的气味。这些生态相互作用可以在作物保护中被利用，通过使用有吸引力的气味把害虫拉进陷阱，使用驱虫剂的气味把害虫从作物上赶走，吸引天敌（捕食者和寄生蜂）来控制，或者甚至同时使用两种气味作为推拉策略的一部分。在虫害管理中广泛探索了使用具有吸引力和驱虫剂的合成气味，但对小农来说，即使这种技术也是负担不起的。吸引人气味和驱虫剂气味的进一步发展是它们可以通过植物传递，选择或改造作物植物来产生驱虫剂气味，选择伴侣植物来产生吸引人的气味。这种伴作方法在非洲的谷类作物蛾类病虫害管理方面取得了显著成功，迄今已有10万多个小农采用了这种方法。成功的一个关键原因是，这种方法适合小农使用的传统混合种植系统。在受控条件下，利用玉米和秋粘虫（FAW）的不同品种进行的实验表明，某些品种的气味变化比其他品种更快、更强烈，以应对秋粘虫（FAW）的损害，并对寄生蜂产生吸引力。此外，如果害虫开始远离受损植株，暴露在一汽受损玉米气味中的相邻未受损玉米植株会对一汽损害做出更充分的准备（激活）。如果我们能确定巴西玉米产区常见的玉米品种对一汽危害的这种反应，并确定对一汽比玉米更有吸引力的伴生植物，并且在受到一汽危害时能发出防御激活气味，那么我们就有机会在巴西玉米作物中开发一种用于一汽管理的伴生方法。我们将在实验室中筛选巴西玉米种植区流行的玉米品种，看它们对FAW危害的防御反应和对天敌的吸引力；在田间筛选对FAW危害有反应并能吸引天敌的玉米品种，以增强天敌的存在和抑制FAW种群；在实验室中筛选同伴植物对FAW的吸引力和激活邻近玉米植物防御导致天敌吸引的能力；将鉴定的玉米系和伴生植物组合在一起，在田间进行筛选，以增强天敌的存在和抑制FAW种群；向小农户展示新技术。

In Brazil, maize is an important crop, providing a source of carbohydrates, vitamins and minerals in the diet. Many small farms in Brazil are run as a family business and provide subsistence for the family, and therefore economic prosperity and survival can depend entirely on the success of the maize harvest. Unfortunately, many insect pests attack maize plants, causing severe crop losses from insect damage. Although maize can be protected from pests by pesticides and even some alternative pest management tools eg pheromones that affect pest behaviour, most if not all of these options are unaffordable for smallholder farmers and there is no other management option available. It is vital that new strategies to defence vital maize crops are developed.Insect pests use their sense of smell to detect and locate suitable host plants for feeding and egg-laying. The odour of host plants comprises of attractive volatile compounds, but when pests start to damage the host plant, the odour changes as plants defend themselves and they become unattractive to the pests. A further development of this phenomenon is that the natural enemies of pests are 'tuned in' to the odour produced by plants when they are damaged by pests. These ecological interactions can be exploited in crop protection by using attractive odours to pull pests into traps, using repellent odours to push pests away from crop plants and attract natural enemies (predators and parasitic wasps) for control, or even using both sets of odours at the same time as part of a push-pull strategy. The use of synthetic attractive and repellent odours in pest management has been extensively explored, but for smallholder farmers, even this technology is unaffordable. A further development of the use of attractive and repellent odours is that they can be delivered by plants, with crop plants being selected or engineered to produce repellent odours and companion plants being selected to produce attractive odours. This companion cropping approach has been adopted with outstanding success in Africa for moth pest management on cereal crops, with more than 100,000 smallholder farms adopting it to date. One of the key reasons for success is that the approach fits with traditional mixed cropping systems used in smallholder farming. Experiments under controlled conditions using varieties of a plant called maize and a moth commonly known as Fall Armyworm (FAW) showed that certain varieties changed their odour more quickly and powerfully than others in response to FAW damage and became attractive to parasitic wasps. Furthermore, neighbouring undamaged maize plants that were exposed to the odour of FAW-damaged maize became more prepared (activated) to respond to FAW damage, should the pest start to spread away from damaged plants. If we can identify this response to FAW damage in maize varieties that are popular in maize-growing regions in Brazil, and identify companion plants that are more attractive to FAW than maize and can emit the defence activating odour when damaged by FAW, then we have an opportunity to develop a companion cropping approach for FAW management in maize crops in Brazil.We will screen, in the laboratory, maize varieties that are popular in maize-growing regions in Brazil with respect to their defence response to FAW damage and attractiveness to a natural enemy; screen in the field, maize varieties that have been identified as responding to FAW damage and attracting natural enemies, for enhanced presence of natural enemies and suppression of FAW populations; screen, in the laboratory, companion plants with respect to their attractiveness to FAW and ability to activate defence in neighbouring maize plants leading to natural enemy attraction; put combinations of identified maize lines and companion plants together in the field and screen for enhanced presence of natural enemies and suppression of FAW populations; show the new technology to smallholder farmers.