What a Tangled Food Web
Abstract:Australian grain growers fight a constant battle against an army of invertebrate pests which chew and suck their way through crops, sometimes spreading disease as they go. But not all of the invertebrates present are pests. There is an equally wide array of natural enemies that can help suppress pest populations. Some natural enemies are there all year, others recolonise with each new crop. Most make their living for some part of the year in other crops and non-crop vegetation. However, some natural enemies, particularly parasitoids, are quite specific about what they will eat. To get the most out of natural pest control, the farmer needs the right natural enemies to be around when their worst pests are. While these invertebrates are an obvious feature of any environment, what is not so obvious is that each of these species is part of a complex network of hundreds of species all interacting with one another in a variety of ways. Even species that seem relatively isolated from one another in time and space are caught up in this 'tangled web'. These interactions between species are important because they are essential to the proper functioning of the ecosystem. They form the basis of processes such as pollination, natural pest control, waste decomposition and seed dispersal. These all come under the umbrella of ecosystem services, the products of nature that contribute to human well-being. These benefits can be wide ranging but, from the point of view of food webs, pest control and pollination are two that are important to farmers. The activities of beneficial invertebrates such as predators (for example spiders and ladybirds) and parasitic wasps that are already present in crops and other on-farm vegetation can help suppress pest populations. While it is obvious that a predator might eat a pest, the extent to which natural pest control occurs depends on many factors – what crop is being grown where, what permanent vegetation is around, how much and what types of insecticide are used and the weather.
Keywords: BENEFICIALS; BROAD ACRE; BROAD-ACRE; CANOLA; CROP; CROPS; ECOSYSTEM; ECOSYSTEM SERVICES; FOOD WEB; INSECTICIDE; INTERACTIONS; INVERTEBRATES; NATURAL ENEMIES; NON-CROP; PARASITES; PEST CONTROL; PESTS; POPULATIONS; PREDATORS; VEGETATION; WEB
Document Type: Research Article
Publication date: 2010-06-01