Petering out pesticides.

• Author: Leu, Andre
• Position: Ecology - Farming systems

ONE OF THE MOST effective ways to reduce the health and environmental risks from pesticides is to replace them with nonchemical methods. Organic farming is not a system of neglect. It negates the need for synthetic pesticides by using cultural and ecological management systems as the primary control for pests, weeds, and disease--with a limited use of natural biocides of mineral, plant, and biological origin as the tools of last resort.

The pesticides used in organic systems are from natural sources and are permitted to be used only if they biodegrade rapidly, which means that there are no residues on the products that people consume. By using cultural and ecological methods as the primary management tools with the aims of firstly preventing pests and secondly controlling them, the utilization of these pesticides is minimal. Research shows that, where these natural pesticides are employed in organic systems, the amounts are some 90% less than the synthetic pesticides used in conventional farming.

An emerging strategy for replacing pesticides, including natural ones, advocates using ecological management systems that can provide functional services, such as employing natural enemies to control pests. The key is to identify these ecofunctions and then intensify them in the farming systems so that they replace the need for insecticides. Ecofunctional intensification (EFI) is used in organic agriculture to utilize ecological processes rather than chemical intensification. A good example of this is adding insectaries into the farming system. Insectaries are groups of plants that attract and host the beneficial arthropods (insects, bugs, spiders, etc.) and higher animal species. These are the species that eat arthropod pests in farms, orchards, and gardens. They are known collectively as beneficials or natural enemies.

Many beneficial arthropods have a range of host plants. Some useful species--such as parasitic wasps, hoverflies, and lacewings--have carnivorous larvae that eat pests. However, the adult stages need nectar and pollen from flowers to become sexually mature and reproduce. Flowers provide beneficial arthropods with concentrated forms of food (pollen and nectar) and increase their chances of surviving, immigrating, and staying in the area. Very importantly, flowers also provide mating sites for beneficials, allowing them to increase in numbers. Without these flowers on a farm the beneficial species die and fail to reproduce. Most...