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

在巴西，玉米是一种重要的农作物，是饮食中碳水化合物、维生素和矿物质的来源。巴西的许多小农场是作为家族企业经营的，为家庭提供生计，因此经济繁荣和生存完全取决于玉米收成的成功。不幸的是，许多害虫攻击玉米植株，导致农作物因虫害而严重损失。虽然玉米可以通过杀虫剂甚至一些影响害虫行为的替代害虫管理工具(如信息素)来保护，但这些选择中的大多数(如果不是全部)对小农来说负担不起，而且没有其他可用的管理选择。至关重要的是，开发新的策略来防御重要的玉米作物。害虫利用它们的嗅觉来检测和定位适合取食和产卵的寄主植物。寄主植物的气味由诱人的挥发性化合物组成，但当害虫开始损害寄主植物时，随着植物自卫，气味会发生变化，对害虫变得不具吸引力。这一现象的进一步发展是，当害虫破坏植物时，害虫的天敌会对植物产生的气味“调谐”。在作物保护中可以利用这些生态相互作用，方法是使用诱人的气味将害虫拖入陷阱，使用驱虫剂气味将害虫从农作物中赶走，并吸引天敌(捕食者和寄生蜂)进行控制，甚至将这两种气味同时使用作为推拉策略的一部分。在害虫管理中使用合成的诱人和驱避性气味已经得到了广泛的探索，但对于小农来说，即使是这种技术也负担不起。诱人和驱避性气味使用的进一步发展是，它们可以通过植物传递，选择或改造农作物产生驱避性气味，并选择伴生植物产生诱人的气味。这种配套种植方式在非洲谷类作物害虫管理方面取得了巨大成功，迄今已有100 000多个小农农场采用了这种方法。成功的关键原因之一是，这种方法符合小农耕作中使用的传统混合种植制度。在受控条件下使用一种名为玉米的植物和一种通常被称为秋粘虫(FAW)的飞蛾的品种进行的实验表明，某些品种比其他品种更快、更有力地改变它们的气味，以响应FAW的损害，并对寄生蜂产生吸引力。此外，暴露在一汽受损玉米气味中的邻近未受损害的玉米植株变得更加准备(激活)，以应对一汽受损，以防虫害开始从受损植株扩散开来。如果我们能够在巴西玉米产区流行的玉米品种中识别这种对一汽伤害的反应，并找到对一汽更具吸引力的伴生植物，并且在一汽伤害时能够发出防御激活气味，那么我们就有机会为巴西玉米作物的一汽管理开发一种间作种植方法。我们将在实验室筛选在巴西玉米产区流行的玉米品种，这些玉米品种对一汽伤害的防御反应和对天敌的吸引力；在田间筛选已确定对一汽损害作出反应并引诱天敌的玉米品种，以加强天敌的存在和对一汽种群的抑制；在实验室根据其对一汽的吸引力以及在邻近玉米植株中激活防御以吸引天敌的能力来筛选伴生植物；将已确定的玉米品系和伴生植物的组合放在田间并筛选以加强天敌的存在和抑制一汽种群；向小农展示新技术。

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.