Natural Pest Control: Capturing the Benefits for Australian Cotton Growers

Natural pest control is one of the ecosystem services provided by nature from which cotton growers benefit. Worldwide, it is estimated that beneficial invertebrates provide pest control valued at US$ 400 billion per year. Most farmers understand very well how to manage their land to maximise crop production. However, while they value services such as pest control, many have yet to develop the knowledge that will let them manage their landscapes in ways that encourage beneficial invertebrates. While it might be clear to growers that clearing land to grow more crops could increase their profits, the economic value of natural pest control generally goes unrecognised. This means that management systems that preserve these benefits are poorly developed. So, how can we make better use of this ecosystem service? While cotton growers benefit from beneficials, many farm management practices can impact on any beneficial invertebrates that are present. If natural enemies are to be effective and encouraged, negative impacts need to be minimised. This can be done by: knowing which are the most effective beneficial species; using targeted soft-option chemical sprays; not spraying till thresholds are reached; and growing crops such as Bt cotton which require less insecticide input. It is also essential to consider cotton pest problems beyond the crop boundary. For example, in agricultural landscapes, the presence of perennial non-crop habitats such as native vegetation remnants are thought to play a crucial role in maintaining populations of natural enemies of pests. These remnants can provide refuge from insecticide sprays, shelter, nectar resources for food, alternative hosts and prey. Many in the cotton industry are already managing their land in ways that minimise impact on beneficial species. For the past 10 years, cotton growers have been combining integrated pest management (IPM) with the growing of Bt cotton and this has improved in-field pest control. They have been helped by beneficial insect guides which allow them to choose chemical sprays that are less harmful to the beneficial species they are trying to protect. These guides are key decision support tools that enable growers to incorporate the management of beneficials into their spray decisions. Additionally, the development of thresholds for pests and adherence to threshold spraying recommendations has reduced the number of sprays and amount of insecticide used. That said, the beneficial insects still have to be in the cotton fields at the right time. Effective pest suppression will almost certainly depend on the natural enemies already being around when the pest arrives in the crop. This will depend on a complex set of issues such as: how well the insect can disperse; a source habitat where they can live before they immigrate to cotton; and their ability to track down prey. The composition of cotton landscapes, specifically the presence of perennial, native vegetation, can greatly influence these processes.