CONCLUSIONS AND RECOMMENDATIONS
- From the reports given herein it is clear that scientific and technical institutions have carried out a huge work to development new alternatives to replace the present use of MeBr as soil fumigant.
- In some countries, such as Spain and USA (Florida), it is evident the existence of various validated alternatives that can already be used by growers in several high-income crops, such as strawberries, tomatoes, peppers and others.
- Brazil has conducted an excellent work on tobacco and in the implementation of the float system to produce tobacco seedlings. This soilless technology has been previously developed in temperate areas of the USA and still may need some modifications to adapt it to hot-climate environments, e.g. to define the need to use plastic film cover, which may increase plant transpiration and, subsequently, decrease plant vigor.
- In general soilless alternatives need a heavy initial investment for their implementation and also good technical services. Not all farmers may afford these methods unless donors, or governments, provide an initial investment, which should come with a regular technical assistance regarding the substrate, nutrients to be given and additional pest control.
- Some alternatives although effective are not always a guarantee of pest control efficacy. This is the case of soil solarization, which highly depends on prevailing air and soil temperatures. If the temperatures are not high the method may fail to control soilborne pests and this may be a risk for farmers' production. The combination of soil solarization with other methods seems to be an effective way to improve the results and to reduce the uncertainty of solarization alone.
- A very effective method is biofumigation, provided that organic waste, manure, etc. are available in farm areas. Biofumigation well managed seems to be more reliable than soil solarization. The method itself is also environmentally safe. In some areas the method cannot be implemented if there is not enough organic waste to use.
- Crop rotation is a well-known and very effective control measure, but the problem is that normally farmers using MeBr are those growing high-income crops. Therefore it appears unlikely that they will adopt widely this practice because crops involved in the process of rotation will never give the same high income as those currently treated with MeBr.
- 8. The use of resistant cultivars and grafting are suitable measures to be integrated in the control system to be adopted. These methods allow to control specific pests, but not the whole complex.
- 9. In Japan, an economically wealthy country, there are other possibilities using water as the main control agent. The Japanese institutions have developed a generator of hot water, which is highly effective in soil-borne pest control and is used in several seedbeds and nurseries. Flooding is also a viable alternative in this country.
- The Japanese use also a plastic film, which is non permeable and enables the farmers to reduce the rates of MeBr and also of other chemical fumigants. The problem of this new synthetic material is its present high price.
- The use of chemical fumigants, such as metam sodium, dazomet, 1.3 dichlorpropene, chlorpicrin, is also possible, but the adoption of any of these chemicals will depend on the economy of farmers. In addition, farmers should take various safety measures to handle and apply these chemicals, some of them as toxic as MeBr. A possibility is the use of any of these fumigants at reduced rates combined with other physical control methods, e.g. soil solarization.
- Integrated pest management (IPM) can be a real option, provided that farmers have some knowledge of the main soil-borne pests present in the soil. With such knowledge it is possible to implement specific control measures, or low-toxic pesticides, aiming at the direct control of the organisms really present in the soil, e.g. nematodes, weeds, or any other pathogens. IPM requires that the farmers have a knowledge of the main pest organisms and not only a knowledge of the possible control measures to be implemented.
For best IPM performance in areas traditionally treated with MeBr, it is essential to develop a training process with a large participation of agricultural extensionists and farmers.
- Developing countries still need to develop their own alternatives and the process of adoption of new alternatives can be speeded up with farmers' training combined with validation of alternatives. Instead of having separate demonstrations where farmers are simple observers, it is necessary to have an approach where farmers learn and at the same time adapt the proposed alternatives to their own situation. In this way the money used for the introduction of new alternatives into the agricultural practice will be efficiently used.