Pesticide resistance: Assessment of risk and the development and implementation of effective management strategies

Insecticides, fungicides and herbicides are critical to successful crop pro duction, but the development of pesticide resistance is a continual threat, especially to many of today's selective toxophores with specific binding s ites. In order to manage resistance effectively, an assessment of genetic, ecological and operational risk factors is required, which must then be tra nslated into meaningful local strategies that can be implemented through ap propriate labelling of products and education of end users. Assessing resis tance risk is a fundamental part of the development process for new molecul es and is increasingly becoming a requirement of registration alongside tox icological and environmental risk data. Laboratory studies, including eluci dation of target sites and metabolic degradation pathways, mutagenesis, com puter models and cross-resistance tests, and field studies, including estab lishment of baseline sensitivities and evaluation of anti-resistance strate gies, all play a part in such assessment. The challenge is then to devise m anagement strategies which are relevant to local practice and actually redu ce selection pressure to a point where product life is preserved. A prevent ative strategy should be in place at time of launch and for most pesticides , regional co-operation between all interested parties, of the kind advocat ed by the Resistance Action Committees of GCPF (Global Crop Protection Fede ration), increases the chance of success. Implementation of strategies via a universal product labelling system, already practised in some herbicide m arkets, is seen as a key way to improve product usage patterns. Monitoring resistance levels in field populations after product launch enables any fin e tuning of tactics over time, for example in response to new technologies such as transgenic varieties being introduced. The limited successes in res istance management in Australia, Zimbabwe, Europe and USA are not so easily achieved in small-holder farming in developing countries, as exemplified b y continuing problems in parts of India and China. Emphasis must be given t o the education of growers and dealers in IRM and IPM, and improved extensi on services, in order to bring about a more sustainable approach to crop pr otection. (C) 1998 Society of Chemical Industry.