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Editor's Notes

• #29: The five basic components of IPM are: < identification < monitoring < thresholds < methods of control < evaluation. Pesticide Selection The following is a guide to the major points which should be borne in mind when selecting a pesticide. Pest Identification and Population Identify the pest accurately then refer to product manuals, advisors, or literature to identify the product or products that will do the job. When scouting pests, it is also important to accurately assess population levels. If pest populations are below economic threshold levels there may be no reason to spray at all. Identification and Population of Beneficial Organisms It is also a good idea to assess the kinds of numbers of beneficial organisms in the field. If their numbers are high they may be able to control the pest without spraying. Additionally, spraying may do more damage to the beneficials resulting in a more serious pest problem than would have occurred without spraying. If beneficials are present and spraying is indicated, you should choose a pesticide that has the least effect on beneficials. Level of Infestation/Stage of Crop Development Assess the number of pests or immature stages such as eggs, larvae and whether the observed level poses an immediate threat. Government department (Ministry of Agriculture or Health) often set "thresholds" above which it is necessary to control pests. It is, however, important to relate the infestation to the stage of crop development. After establishing the nature and level of the infestation and having identified a range of products that will bring it under control, it is necessary to select the most appropriate product. The following criteria should be applied: Selectivity High selectivity is not very common but if possible, choose the pesticide that will cause the least damage to non-target species. Mammalian Toxicity Products that are of low toxicity to man and other mammals are preferable to those which pose significant hazard. Method of Application Match the product to the available equipment for application. Certain formulations cannot be used with knapsack or other hydraulic sprayers. Persistence Check the product label for information about the persistence or length of activity. In certain circumstances, it is useful to have a product which will remain active for several days or even weeks. If an infestation occurs shortly before harvest, choose a product that will not leave residues which may be harmful to consumers. Check for the pre-harvest interval in the product labels. Mode of Action Bear in mind that products work in different ways. Knowledge of pests and how a certain product works can help you maximise the effectiveness of the product. Avoidance of Resistance With chronic infestations, i.e. those which may continue throughout the season and which may need several applications for even partial control, do not spray repeatedly with the same product or family of products. For example, early in the season use a relatively selective product to minimise damage to predators and other beneficial insects. Later in the season choose a broad spectrum if necessary.