Importance of arthropod pests and their natural enemies - HGCA

ate of repopulation depends on many complex and interacting factors including the susceptibility of the eachspecies, the spatial extent of the application in conjunction with the natural enemies mobility and theproportion that remained unaffected in the landscape. Integrated Pest Management guidelines include manysuggestions on how to reduce the effects of insecticides and these are reviewed below.4.5 Impact of habitat manipulation on pest natural enemiesIn this section of the review the potential to enhance levels of pest control using habitat manipulation wasexamined with an emphasis on those habitats that can be created using Environmental Stewardship (ES)schemes. The focus is on those schemes currently being funded. Other approaches that aim to enhancenatural enemies exist but have been adequately reviewed in the existing literature and most apply to cropsother than cereals or oilseed rape (Landis et al., 2000; Wäckers et al. Eds, 2005; Gurr & Wratten, Eds, 2000).The suite of ES schemes introduced in 2005 have a number of aims, but, like their predecessors, theimprovement of biological control (biocontrol) of insect pests is only considered for beetle banks.Nevertheless, our understanding of the ecology of pest natural enemies is sufficient to conclude that many ofthe habitats created under Entry Level Stewardship (ELS), Organic Entry Level Stewardship (OELS) orHigher Level Stewardship (HLS) have the potential to enhance or support populations of pest naturalenemies (Holland, 2007). To achieve the most effective pest control it is necessary to provide the following:• Resources must be sufficient to ensure the survival and reproductive capacity of natural enemies ismaintained or improved.• The farmed landscape must permit movement between non-crop habitats and crops or between cropsensuring an even distribution of natural enemies during the pest infestation.• A diversity of natural enemies with a range of phenologies and feeding habitats must be present toensure that the pest is attacked throughout its lifetime and by a variety of ways.• In the case of parasitic species, it may be necessary to allow the pest to survive outside of the cropensuring that the parasites survive in the locality.Overall the contribution that the ES options make towards achieving the first of the above is best understood.The biology and consequently resources required by natural enemies were investigated for many of the morecommon taxa and consequently inferences about how the ES options will contribute to their survival can bedetermined. These essential resources include:1) Pollen and nectar. Floral resources are utilised by a broad range of predators and parasitoids because theyprovide energy and can act as an alternative food source (Wäckers, 2005). For parasitoids a source of nonhostfood can influence many facets of their biology that ultimately affect the levels of biocontrol achieved42