Conservation Biological Control of Insect Pests

Abstract

The human population is predicted to reach 9 billion by 2050. To achieve food security for this growing population, agricultural intensification is occurring, with increasing use of pesticides to reach the necessary yields. However, there is strong evidence that suggests pesticides cannot provide the agro-ecosystem growth and stability needed for the increasing demand. It is well established that pesticides are harmful to human, animal and environmental health. This information has reached the public, causing some governments to create policies that require the reduction of pesticide inputs in agro-ecosystems. Consequently, there is a need to manage pests using alternative techniques. One such approach is to enhance an ecosystem service (ES) which is conservation biological control (CBC). This is defined as manipulating the agro-ecosystem to enhance natural enemy fitness, populations and efficacy to suppress pest numbers. The problem is, not every study that has added multiple resources to agro-ecosystems is successful. Such resources may act synergistically and provide multiple ES delivery or include elements of redundancy, competition, or generate ecosystem dis-services. Here, we synthesize current reviews, provide a critical analysis and indicate future strategies. The key area that needs more focused research is understanding why floral resources are not always successful in the enhancement of natural enemy populations that lead to top-down pest suppression. Associated with this challenge, there are large knowledge gaps in natural enemy non-consumptive effects on prey and how these can be manipulated and used in CBC. For example, adding flowering plants to an agro-ecosystem is likely to impact several invertebrate and vertebrate communities, not always positively. These effects may, however, only be short term and localized. Existing landscape complexity has potential to supplement local effects but this is a highly multivariate approach. Major impediments to CBC being widely deployed certainly do not include cost. A typical 100 m × 2.3 m vineyard inter-row with buckwheat seeds costs only US $2.00. Key limitations to uptake of CBC by farmers and growers include: individual government policies which are inimical to agro-ecological approaches; the marketing power of agro-chemical companies; farmer innate conservatism; and most importantly, a weak emphasis of delivery systems and pathways to implementation. The most effective way to addressing the latter is ‘farmer field schools’, led by ‘farmer teachers’. Outputs do not lead to outcomes unless multiple delivery systems and pathways of implementation are involved and developed at the beginning of the research.