May 20, 2013: Bhutan 2013 Rust Surveys – Rust incidence lower than 2012, leaf rust widespread but yellow rust localized


Rust surveys were coordinated and undertaken by the National Plant Protection Centre, Department of Agriculture, Ministry of Agriculture and Forest, Semtokha, Thimpu, Bhutan in collaboration with the Durable Rust Resistance in Wheat (DRRW) project during the period 25th April – 3rd May 2013. Surveys were undertaken in the western (Paro, Punakha valleys) and central (Bumthang) wheat growing areas. A total of 31 sites were surveyed. leaf rust was the most widespread disease, being recorded at 45% (n=14) of the sites surveyed. Leaf rust was observed in all the areas visited but incidence and severity was highest in the Punakha area. Two newly released lines from Nepal, being evaluated at Bajo Research and Development Centre, were susceptible to leaf rust and this may indicate exposure to different races of leaf rust in Bhutan.

Surprisingly, given the regional context and seemingly favourable climatic conditions in 2013, yellow rust was only found at very low incidence in Bhutan. Yellow rust was only observed at 8 sites on the survey and all but two of these sites only had trace amounts of disease. One site – Susuna in southern Paro – had exceptionally high incidence and severity of yellow rust. With a single field (1-2 ha) of an unknown improved variety exhibiting 100% incidence and 60-70% severity. Neighbouring fields of local cultivars appeared virtually disease free.

No positive observation of stem rust was obtained on the field survey. As on the previous survey in 2012, flag smut (Urocystis agropyri) was observed at two locations. These locations differed from those recorded in 2012. Current observations confirmed the presence of this disease at low frequency in Bhutan.


Considerable attention was given to Berberis species on the Bhutan rust survey. Berberis sp. were extremely common in all the wheat growing areas visited. From field observations it was considered likely that up to 8 different species of Berberis were present along the survey route. Efforts to conclusively identify these different species are on-going. Two distinct species of Berberis were found to be infected with aecia, with infected bushes observed at 4 unique locations (including the Susuna site with high incidence of yellow rust. Infected Berberis were also observed at this location in 2012). Several aecial samples and rust samples were collected on the survey and are currently undergoing analysis.


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