Complex members isolated from the tropical grass Digitaria have been more narrowly defined as M. grisea. The remaining members of the complex isolated from rice and a variety of other hosts have been renamed Magnaporthe oryzae. Confusion about which of these two names to use for the rice blast pathogen remains, as both are now used by different authors. Management of rice blast includes use of resistant varieties, seed treatment with systemic fungicides, balanced use of fertiliser, use of compost, and sanitation were recommended. Available BCA include Trichoderma spp., Bacillus subtilis, Corynebacterium sp. and chitosan. Although Trichoderma spp. and B. subtilis (Indonesia), and Trichoderma spp. and Chitosan (Vietnam) are commercially available in the respective AMS, they appear not to be particularly registered for application against rice blast (according to the ABC database). Box 1: Application of Trichoderma harzianum for management of rice blast Field trials to test the effectiveness of Trichoderma species in controlling rice blast were jointly planned in the Regional BCA Expert Group on Application and implemented in Lao PDR (under supervision of the Plant Protection Centre in Vientiane) and in Cambodia in four provinces: Prey Veng, Kampong Chnang, Battambang and Kandal (under supervision of the DOA). Although not all data could be evaluated at the time of writing this document, preliminary results from Battambang in Cambodia were highly encouraging. Four treatments (with four replicates) were compared: T1) negative control without composting, T2) negative control with composting, T3) treatment with Trichoderma harzianum added to compost, T4) T. harzianum added to compost and sprayed on leaves four times. While moderate infestations with rice blast were recorded in T1, none were seen in the other treatments. Great differences were observed in rice yields at harvest: While composting alone (T2) doubled average yields from 2 (T1) to 4 tons ha-1, application of T. harzianum further increased yields to averages of 5.5 tons ha-1 (T3) and 6.1 (T4) tons ha- 1. While T3 and T4 were not significantly different, all other pairwise comparisons of treatments were statistically different. An economic evaluation is under preparation. Apparently, application of compost alone already controlled rice blast infection. Importantly, the fungal treatments visibly improved root growth of the rice plants confirming earlier studies that Trichoderma has a positive impact on the overall plant nutritional status besides disease control. The lesson learnt from this trial is that proper nutrient management and biocontrol can go hand in hand for achieving optimal results. An important publication that provides a good overview over the properties and functions of Trichoderma fungi was published in the year 2000 already, but is still relevant today (77). 31 The positive effects of biocontrol with Trichoderma could be directly observed by the Regional BCA Expert Groups in vegetable fields during the excursion that was linked to the Project Partner Meeting in Cambodia on 13 March 2014. The field trip was hosted and directed by Dr. Kean Sophea of the DOA, Cambodia, who had arranged demonstration plots in tomato, cucumber and other vegetables. Generally taller and healthier plants could be observed in treated fields and local farmers were content with the results.
Implementing Biological Control Agents in the ASEAN Region
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