Integrated pest management
This topic is sponsored by AgrEvo Pty Ltd.
Twenty-five years ago cotton cultivation was abandoned in Western Australia's Ord River valley because of an uncontrollable infestation of two native caterpillars. Now researchers are trialling an integrated pest management strategy that could allow cotton to be grown there again.
Just as there is more than one way to skin a cat, fry an egg or eat an ice-cream, there are many ways to beat agricultural pests. Combining different pest control strategies is the basis of integrated pest management (Box 1: Pest control techniques). It can be applied, in theory at least, to any kind of pest vertebrate, invertebrate, plant, bacteria, fungi or virus.
In part, the development of integrated pest management (IPM) is a response to the failure of many chemical pesticides to provide long-term solutions to pest problems. While some pesticides have dramatic effects when first applied, many pests develop resistance to the chemical over time and often re-emerge to plague an industry. It can become a vicious circle the farmer increases the rate of pesticide application, producing increasingly resistant 'super-bugs'. Large quantities of the poisons enter the soils and waterways of the region, with sometimes unforeseen and devastating effects on the environment and human health.
Pest resistance in the Ord
When large plantations of cotton were established in Western Australia's Ord River valley in the 1960s, the caterpillars (larvae) of two species of heliothis moth moved in. These destructive pests were controlled initially by pesticides, but, pretty soon, they started developing resistance. Farmers kept increasing the dosage, but they were fighting a losing battle. Eventually, as landholders went broke, switched to other crops or simply abandoned their properties, the industry collapsed.
Now, 25 years later, researchers are trialling an integrated pest management strategy to see if commercial cotton can again be grown in the Ord River valley. Many elements of the strategy were first developed in the Namoi Valley in New South Wales, another cotton-growing area. The strategy includes:
- Vastly improved understanding of the ecology and biology of
pests and the crop itself.
- Monitoring the increase in insect pest numbers. This, combined
with an understanding of their life cycles, allows pesticide spraying at the most effective times, reducing the need for large amounts
- Using different types of insecticides to reduce the likelihood of resistance to any one chemical building up.
- Increasing the numbers of natural predators. One of the side effects
of high rates of pesticide use is that insects and other small
animals that might otherwise feed on cotton pests are killed.
As application rates decline, more of these beneficial animals
survive and are able to play a more active role in suppressing
- Cotton plant varieties that have been genetically engineered. They now include a gene taken from a bacterium (Bacillus thuringiensis, or Bt) that produces a protein which is toxic to heliothis caterpillars.
The key components of integrated pest management
Successful integrated pest management usually has several key components.
- Knowledge. Understanding
the biology and ecology of the pest, and the crop (or livestock)
is essential. Information about interactions within agricultural
ecosystems is also important. IPM draws on the fundamental knowledge
of plant and insect biology accumulated by biologists.
- Monitoring. Farmers
can use relatively simple techniques to keep track of what pests
are where. This information, combined with knowledge of pest life
cycles, can enable farmers to implement control measures at the
most effective times.
For example, the pyrgo beetle is a major defoliating insect pest of tea tree in Australia. In the past, growers have used large quantities of chloropyrifos spray to control the beetle, but this chemical has been showing up as an undesirable residue in tea-tree oil products. Clearly, better ways are needed. Field trials have demonstrated that the placement of yellow sticky traps within tea-tree plantations gives growers an accurate picture of beetle distribution at an early stage of their life cycle, enabling better targeted control programs. These would reduce both the need for and the cost of applying chemical sprays.
Monitoring on a broader scale can also be used to predict pest outbreaks and forewarn farmers to take action. For example, scientists at the Cooperative Research Centre for Tropical Pest Management have developed a computer model that can predict the migration of the heliothis moth using information on wind patterns and satellite data about the status of host plants and breeding sites.
- Economic threshold. This takes into
account the revenue losses resulting from pest damage and the
costs of treatment to prevent the damage. Below the economic threshold, the presence of the pest is tolerated. Only when pest numbers increase above the threshold does the farmer take action.
- Adaptability. Farmers must keep informed about what is happening in their paddocks so that they can adapt their strategies to changing circumstances. Research scientists, too, must aim to keep at least one step ahead of the pest, which is also undoubtedly changing and adapting over time.
A wide range of pest control techniques is available to farmers. Some of them are as old as agriculture itself rotating a crop, for example, to avoid a build-up of host-specific pests. Some are new in recent years, genetic engineering has opened up many possibilities in pest control that were unavailable to agriculturalists even a decade ago.
But farmers using integrated pest management don't hang their hats on any single technique. The simple philosophy is that control will be more effective, and resistance will be less likely to build up, when a range of measures is deployed against a pest (Box 2: Integrated pest management in the Australian apple industry). Wherever possible, different pest control techniques should work together rather than against each other. In some cases, this can lead to synergy where the combined effect of different techniques is greater than would be expected from simply adding the individual effects together.
Fighting the good fight
Our knowledge of agricultural systems and their associated pests will continue to expand, enabling management efforts to become increasingly subtle, increasingly effective and increasingly benign to the environment.
Farmers should benefit too, from reduced handling of potentially toxic chemicals and from the increased satisfaction that comes with a heightened awareness of the farm ecosystem. They may feel less pain in the hip pocket, because the savings from the reduced use of pesticides will often outweigh the cost of integrated control measures. And the long-term sustainability of the farming systems may also be enhanced.
Pest control is a continuing struggle, because rarely are pests totally eradicated (and, in the case of native pests, this may not even be desirable). The ways are many, but the aim is the same: to find a balance, precarious though it may be, between the impact of the pest and the effort needed to suppress it.
Page updated August 2001.