RESUMO
One promising area of disease management for resource-poor farmers that emerged in recent years in developing countries is the potential of biological control. Biological control agents (BCAs) were found to be ubiquitous in the rice ecosystem. Seed bacterization with BCAs appeared to promote plant growth. BCAs showed efficacy on sheath blight (Rhizoctonia solani AG 1) but produced inconsistent results over time in the field using it alone. The control efficiency ranged from 50 to over 90%, with a high variance. To improve the efficacy, a half-dose of a commonly used fungicide, like Jingangmycin in China and Validamycin in Vietnam, was introduced to mix with BCAs and was found to be effective, and it reduced the variance of the field performance tests. To scale up the BCA technology for resource-poor farmers, a participatory approach, engaging the farmers to evaluate the product, was initiated in China and Vietnam. The BCA strain that is indigenous at a locality is mass produced at the research institution based on the total area required for application, as relayed by the farmers to extension workers. The demand by farmers would serve as the basis for the amount to be produced and for delivery to the rice farmers who were participating in the trials and, later, to those farmers who ordered the product. This process alleviates BCA storage and shelf-life problems. Data from the field performance trials also were used by the researchers to apply for registration for commercial use of BCAs. Scaling up to extend the BCA technology to more rice farmers as an integral part of their pest management scheme, in particular, and crop management practices, in general, is foreseen in the near future.
RESUMO
A protocol for characterizing patterns of rice cropping practices and injuries due to pathogens, insects, and weeds was developed and used in six sites in tropical Asia covering a wide range of environments where lowland rice is cultivated. The data collected in a total population of 456 individual farmers' fields were combined to site-specific weather data and analyzed using non-parametric multivariate techniques: cluster analyses with chi-square distance and correspondence analyses. The main results are: (i) patterns of cropping practices that are common across sites can be identified; (ii) conversely, injury profiles that are common across sites can be determined; (iii) patterns of cropping practices and injury profiles are strongly associated at the regional scale; (iv) weather patterns are strongly associated with patterns of cropping practices and injury profiles; (v) patterns of cropping practices and injury profiles allow for a good description of the variation in actual yield; and (vi) patterns of cropping practices and injury profiles provide a framework that accurately reflects weather variation and site diversity, and reliably accounts for variation in yield. The mean estimated yield across sites (4.12 t ha-1) corresponds to commonly cited averages in the region and indicates the potential for increased productivity with better management practices, especially an improved water supply. Injuries due to pests are secondary compared with other yield-limiting factors. Injury profiles were dominated by stem rot and sheath blight (IN1); bacterial leaf blight, plant hoppers, and leaf folder (IN2); and sheath rot, brown spot, leaf blast, and neck blast (IN3). IN1 was associated with high (mineral) fertilizer inputs, long fallow periods, low pesticide use, and good water management in (mostly) transplanted rice crops of a rice-rice rotation. IN2 was associated with direct-seeded rice crops in an intensive rice-rice rotation, where fertilizer and pesticide inputs are low and water management is poor, or where fertilizer and pesticide inputs are high and water management is adequate. IN3 corresponds to low input, labor intensive (hand weeding and transplanting) rice crops in a diverse rotation system with uncertain water supply. Weed infestation was an omnipresent constraint. This study shows the potential for developing pest management strategies that can be adapted throughout the region, rather than being site-specific.
