A seminar on foliar diseases of wheat and rice was delivered by Dr Namgay Om on 12 November 2019. The event dealt with the findings of surveys conducted during the 2018-2019 season.
The seminar oriented the technical staff of NPPC on unrecorded foliar diseases (in Bhutan) of wheat & barley besides wheat rusts. The seminar summarized that wheat leaf rust though, generally observed in the mid–low altitude areas, is prevalent with low severity along with stripe rust at high altitude places in Bumthang. A complex of stripe and leaf rust is also common in the warm and humid area of Baylangdra, Wanduephodrang. In most areas, farmers grow local varieties. In certain areas, severe stripe rust are recorded on local varieties e.g., Susuna, Dogor, Paro. This necessitates promotion of resistant varieties in such areas. Hence, NPPC and the Wheat Program need to take up the activity. The wheat survey findings also indicated the risk of stem rust. Stem rust has never been recorded in Bhutan. However, in May 2019, symptoms similar to stem rust (big oblong pustules rupturing epidermis with brown colour deeper than leaf rust) were observed in Toebisa, Punakha. Further work is required for proper identification. The seminar also had a session on feedback by the junior officers on challenges in the fields while conducting wheat rust surveys.
The seminar also highlighted on the putative identification of fungal pathogens (Pyrenophora sp., Zymoseptoria tritici & Parastagnospora nodorum) causing different types of leaf spots on wheat and barley. Symptoms caused by different Pyrenophora species are very similar and hard to distinguish in the field. Symptoms produced by Zymoseptoria tritici are quite distinct compared to others. However, most of these diseases may occur as a disease complex causing further confusion to field surveyors. Samples examination revealed occurrence of Zymoseptoria blotch (syn. Septoria blotch) in Choekhor & Tang Gewogs in Bumthang Dzongkhag and Parastagnospora nodorum in Ura Gewog, Bumthang, and Nobgang Chiwog under Samar Gewog in Haa.
On rice, the most important observation was the infection of blast resistant varieties e.g., IR64 and Yusiray Maap with blast pathogen Magnaporthe oryzae. This could be an indication of resistant break down in such varieties. The NPPC needs to follow up with ARDC Bajo for further work on this. Rice brown spot disease was prevalent with varying degree of severity in almost all areas of Paro and Punakha. A complex infection of blast and white tip nematode (Aphelenchoides besseyi) was also detected in Tsento, Paro.
The seminar concluded with emphasis on the importance of sample collection and field notes during surveys. Importance of seed health and adoption of hot water treatment besides use of resistant varieties were some of the main recommendations provided.