Improving biological control in UK organic vegetable growers

在英国，温室草本植物和蔬菜都是高价值的作物。在过去的二十年里，这些作物的产量大大增加，一些生产者是有机的，或者正在考虑转向有机生产。目前，非有机生产者的虫害防治严重依赖于常规化学农药。由于最近的欧盟安全法规，其中许多正在被撤回。欧盟的一项新政策(关于杀虫剂的可持续使用指令，2009/128/EC)是推广环境友好的、基于生物的虫害控制方法。政策环境的这种变化，加上最近的科学和技术进步，为以生物为基础的控制剂创造了真正的机会。然而，以传统化学农药商业化为基础的一种规避风险的老式方法阻碍了新生防剂的发展。现在有机会用新的思维方式来处理这个问题，评估现有的方法，并用新的生物制剂来改进或取代它们。在这个项目中，我们将专注于两种重要作物的生物防治，草本植物，如欧芹和有机辣椒。欧芹是两种常见的害虫，它们分别是麦长管蚜Cavariella Aegopodii和山楂-欧芹二化螟Dyaphim apiifolia。在有机辣椒中，主要问题是绿叶蝉。通常用商业上可买到的寄生黄蜂(寄生蜂)来处理蚜虫物种，最初是作为单一物种，但最近是以有时多达六种不同物种的混合形式。尽管如此，控制通常还不够充分，种植者可能会遭受可接受的损失。另一方面，在培养皿和实验室的试验中，这种寄生蜂似乎是非常有效的。在有机辣椒栽培中，推荐的防治叶蝉的生物剂是卵寄生蜂Anagus tom us。让事情更复杂的是，辣椒还会受到蚜虫的攻击，特别是桃蚜-土豆蚜虫和温室土豆蚜虫Aulacoreum solani。这些通常是使用商业上可用的寄生蜂成功地控制的。不幸的是，利用海藻控制叶蝉往往不成功，种植者必须使用化学杀虫剂来拯救他们的作物，从而失去有机溢价，并扰乱成功的蚜虫生防剂。已经有人建议使用一种非商业作物，即寄主另一种害虫种群的非商业性植物，而海藻可以以这种害虫为食，并积累足够多的种群，使作物上的叶蝉种群保持在较低的水平，但仅取得了混合成功。本博士学位将调查影响成功生物防治欧芹和辣椒害虫的因素。例如，假设商业生产中的间距使寄生蜂很难找到它们的寄主，此外，极快的生产计划--从欧芹萌发到收获3-4周--虽然足够长的时间让蚜虫种群达到危害水平，但不足以使寄生蜂有效地发挥作用。因此，我们将测试种植密度和间距对蚜虫种群生长发育和寄生蜂搜索效率的影响。此外，我们还将研究早期释放寄生蜂的影响。在辣椒中，可能是由于辣椒没有足够早地激活它们的防御系统(众所周知，这些系统会吸引天敌)来响应叶蝉的产卵，或者是银行家的位置不正确或质量不够高，所以很可能是因为辣椒很难找到寄主。我们将测试应用顺式茉莉酸酯是否会刺激植物防御系统，并改善生物防治。银行植物的位置和种类也将被调查。

Glasshouse herbs and vegetables are high value crops within the UK. Production of these crops has increased greatly over the last twenty years and a number of producers are organic or contemplating the switch to organic production. Currently, pest control in non-organic producers is heavily reliant on conventional chemical pesticides. Due to recent EU safety regulations many of these are being withdrawn. A new EU policy (the Sustainable Use Directive on pesticides, 2009/128/EC) is to promote environmentally friendly, biologically based pest control methods. This change in the policy environment, combined with recent scientific and technological advances, creates real opportunities for biologically-based control agents. The development of new biological control agents has, however, been hampered by a risk-averse, oldfashioned approach based on the system in which conventional chemical pesticides were commercialized. There is now an opportunity to approach the problem with a fresh mind-set and to evaluate current methods and to improve or replace them with novel biological agents.In this project we will focus on biological control within two important crops, herbs, such as parsley, and organic peppers. Parsley is commonly attacked by two aphid species, Cavariella aegopodii and the hawthorn-parsley aphid, Dysaphis apiifolia. In organic peppers the major problem is the leafhopper Empoasca decipiens. The aphid species are commonly treated with commercially available parasitic wasps (parasitoids), originally as single species but more recently in mixtures of sometimes as many as six different species. Despite this, control is commonly less than adequate and growers reportunacceptable losses. On the other hand, in Petri dish and laboratory trials the parasitoids appear to be very effective.In organic pepper cultivation the biological agent recommended against leafhoppers is the egg parasitoid Anagrus atomus. To further complicate matters, peppers are also attacked by aphids, in particular the peach-potato aphid, Myzus persicae and the glasshouse potato aphid, Aulacorthum solani. These are usually successfully controlled using commercially available parasitoids. Unfortunately, control of the leafhopper using A. atomus, is often unsuccessful and growers must then use chemical pesticides to save their crop, thus losing the organic premium and disrupting the successful aphid biological control agents. The use of banker crops, i.e. a non-commercial plant hosting populations of another pest insect on which A. atomus can feed and develop and build up to high enough numbers to keep the leafhopper populations at low levels on the crop, has been suggested, but with mixed success only.This PhD will investigate the factors affecting successfully biological control of the pests of parsley and peppers. It is for example, hypothesized that the spacing in commercial parsley production is making it difficult for the parasitoids to locate their aphid hosts and that in addition, the extremely fast production schedule, 3-4 weeks from germination to harvest in parsley, whilst long enough to allow aphid populations to reach damaging levels is insufficient to allow parasitoids to act effectively. We will thus test the effects of planting density and spacing on the growth and development of aphid populations and parasitoid searching efficiency. In addition we will investigate the effect of earlier parasitoid release. In the peppers it is possible that A. atomus is finding host location difficult as the peppers are possibly not activating their defence systems (these are known to attract natural enemies) early enough in response to leafhopper egg laying or that the bankerplants are not correctly placed or of sufficient quality. We will test if applying cis-jasmonate will stimulate the plant defence system and result in improved biological control. The placement and species of banker plants will also be investigated.