Christine Gould argues that transgenic crops have much to offer farmers who use integrated pest management techniques
Do crops that have been genetically modified — for example to increase their resistance to insects and other threats — have a place in integrated pest management (IPM)?
We at CropLife International, the global federation that represents the plant science industry, feel strongly that they do, and that genetic modification is a useful and beneficial technology that can make a significant contribution to sustainable agriculture.
IPM is a system of protecting crops that meets the requirements of sustainable development by allowing farmers to manage diseases, insects, weeds and other pests in a way that is cost-effective, environmentally sound and socially acceptable, as well as appropriate to local conditions.
To achieve this, farmers need to take into account all relevant and locally available pest control tactics. They will adopt and exploit techniques they see as practical and can add value to their activities.
Genetic modification can make a substantial contribution to the options that farmers have available. It can be combined with other practical strategies to optimise IPM programmes, thus preventing pest populations from reaching economically damaging levels.
Indeed, like all technologies that help make crop protection and production more efficient, genetically modified crops are most effective when they are used as part of an IPM system.
Handled with care
The UN Food and Agricultural Organization (FAO) defines integrated pest management as "the careful consideration of all appropriate measures that discourage the development of pest populations and keep pesticides and other interventions to levels that are economically justified and reduce or minimise risks to human health and the environment."
The plant science industry supports this characterisation of IPM — taken from the FAO's Code of Conduct on the Distribution and Use of Pesticides — and in particular the concept that IPM "emphasizes the growth of a healthy crop with the least possible disruption to agro-ecosystems, and encourages natural pest control mechanisms".
A farmer's choice of which crops to plant — and thus the ability to select disease- and pest-resistant ones — has always been a cornerstone of IPM. Crop varieties with disease and pest resistant characteristics — including those produced using precise and targeted transgenic methods — can reduce the need for other protection measures, thus providing greater choice in other areas.
So called Bt crops are a case in point. Gene technology has contributed to the development of plants that express insecticidal toxins using genes from the naturally occurring soil bacterium Bacillus thuringiensis.
Bt toxins have been used as an alternative to chemical insecticides for almost 60 years. They control several important pests, and are regarded as highly selective and environmentally friendly, with decreased impact to other, potentially beneficial, insects. Indeed many farmers, including organic farmers, already use spray formulations containing Bt.
Bt toxins, even when introduced into crops using genetic techniques, are very useful in IPM strategies, which build on natural mechanisms for controlling pest populations. In practice, whether farmers use Bt sprays or plant Bt crops, the issues concerning environmental impact are essentially the same. The main difference, in our opinion, is that Bt crops can help deliver the toxin more effectively, and can reduce the need for conventional insecticides.
A range of options
When assessing any action to combat pests, it is naturally important to distinguish between harmful and beneficial insects. If and when a pest outbreak occurs, a variety of control strategies should be considered, which can be physical, biological or chemical.
At present, farmers in developing countries follow a number of strategies to control pests. These include:
- Growing crops that are appropriate to local climate, soil and topography;
- Rotating crops to limit the build-up of pests and reduce weed problems;
- Not planting crops that can host similar pests next to each other;
- Using efficient irrigation methods;
- Reducing pest pressures in individual crops by inter-cropping;
- Adding soil nutrients to maintain soil fertility and plant health.
In each instance, a variety of factors must be taken into account when deciding which method or combination of methods should be used. These include costs, benefits, timing, available labour force, machines/tools and control agents, as well as economical, environmental and social factors.
With Bt crops, for example, a key element of resistance management is creating a 'refuge' — an area or strip of land planted with non-Bt crop varieties that reduces the environmental pressures encouraging insects to develop resistance to Bt.
As far as other risks are concerned, transgenic crops — like all crops — require routine inspections and observation. This is required to assess how well plants are growing, and what actions need to be taken on cultivation, fertiliser use, and the control of weeds, insects, other pests and disease — as well as when to harvest.
Farmers in control
Other biotech crops also have much to contribute to IPM strategies. Herbicide-tolerant crops, for example, can be useful for farmers pursuing minimum tillage systems, in which fields are left unploughed before sowing, and any weeds present are sprayed with herbicide.
The method can help to reduce labour inputs, enhance soil biodiversity, and lead to more efficient use of water, as well as preserve organic matter and decrease soil erosion. In addition to these benefits, using herbicide-tolerant crops in such contexts can reduce the amount of herbicide used, as well as the risks associated with chemical run-off, and contribute to weed management strategies.
Furthermore, the development of transgenic crops has enabled minimum tillage systems to be expanded into areas where they have been difficult to implement in the past. These farming practices have become popular with farmers worldwide, especially in North and South America, and in China.
Farmers remain the primary decision-makers in IPM programmes. The role of the plant science industry is to provide access to the widest possible range of appropriate technologies, services and products, and as much information as possible on their characteristics, costs and optimal use within IPM strategies.
Transgenic crops are just one such product, and have already a proven a boon to millions of farmers. The evidence endorses our conviction that they have a vital role to play in integrated pest management, indeed in sustainable agriculture more generally.
Christine Gould is communications manager for CropLife International. This article was written with the collaboration of other CropLife staff.
Click here to read an opposing view from G. V. Ramanjaneyulu, executive director of the Centre for Sustainable Agriculture in Secunderabad, India.