• Balanced use of nitrogen fertiliser (avoid overuse) • Reduced seedling density • Sanitation measures Rice stem borers are reported as widespread; however they rarely cause significant crop loss in the common short-duration varieties. Where control is needed (e.g. in long duration, premium varieties), the main biocontrol approach favoured by AMS includes Trichogramma spp. In principle, timing of control is very important for rice stem borer, as this pest is most damaging during the panicle initiation stage. However, availability of BCA appears to be very limited, with state sponsored production of these insects in decline. As with other insect natural enemies, their effectiveness is hindered by widespread overuse of broad-spectrum insecticides. It is important to stipulate how Trichogramma use could be promoted in the future - and which species are actually to be used (therefore more effort put into identification and characterisation). Other BCA against stem borer include botanicals and pheromones. The ABC Project will address the latter with the descriptions of field demonstrations of mass trapping with sex pheromones; the results are not included here, because the demonstrations were still ongoing when this text was written. Large-scale experience with pheromone‐based mass trapping has been described from India (58). The changes in practice recommended for brown plant hopper (e.g. the 40 DAT pesticide moratorium) would also help manage stem borers and other insect pests, because preservation of natural enemies would increase the crop’s natural pest control function. Commercially available and registered products against rice stem borer according to the ABC database only include botanical products based on plant extracts of Croton tonkinensis (Matrine) in Vietnam, and on root extracts of Sphora flavescens (Oxymatrine) in Cambodia (see also Appendix I). The scientific evidence available reflects quite well the recommendations of AMS. There exist various studies on the application of Trichogramma species against rice stem borers. All of them arrive at an effective release rate of around 100,000 adult parasitoids per ha, applied two times as in Indian field trials (57). The published data emphasise that, in the case of macro-organisms, it is important to exactly identify the species of Trichogramma, since they performed differently against various pests in the field. Species-specific sex pheromones are the second major biocontrol approach that has been tested successfully for stem borer control, particularly in India and Bangladesh. A study from 2008 in India compared use of rice stem borer mass trapping (employing sex pheromones) with synthetic pesticides and farmer’s practice (58). The economic analysis also included other input costs (e.g. herbicides, fertiliser etc.) and revealed that pheromone application can indeed replace chemical pesticides in terms of effectiveness and economy. Rice blast, Magnaporthe grisea, an ascomycete fungus, is also known as rice blast fungus, rice rotten neck, rice seedling blight, blast of rice, etc. is a plant-pathogenic fungus that causes an important disease affecting rice. It is now known that M. grisea consists of a cryptic species complex containing at least two biological species that have clear genetic differences and do not interbreed. 30
Implementing Biological Control Agents in the ASEAN Region
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