Development of Melampsora ciliata rust on nursery‐grown poplars in north‐western Himalayas

Development of leaf rust ( Melampsora ciliata ) in different species, hybrids and cultivars of poplar ( Populus spp.) was studied in nursery‐grown plants. Five different criteria were used to assess the disease development. The mean disease index on 10 August was 9.4% which increased to 70.0% on 10 October. The lowest disease index (5.5%) was recorded in P. yunnanensis whereas the maximum was recorded in P . ×  euramericana ‘Rubra‐Poiret’ (59.5%). The apparent infection rate per unit per day was highest in P. nigra  ×  P. trichocarpa (9.7 × 10 –2 ) whereas the minimum occurred in P. maximowiczii  ×  P. berolinensis ‘Oxford’ (3.3 × 10 –2 ). The area under the disease progress curve was a maximum in P.  ×  euramericana ‘Rubra‐Poiret’ (26.7) and a minimum in P. yunnanensis (1.6). Complete defoliation by the first half of October occurred in P. nigra  ×  P. trichocarpa , which also had the maximum apparent infection rate and area under the disease progress curve. Inoculum production was highest in P. nigra  ×  P. trichocarpa and lowest in P. maximowiczii  ×  P. berolinensis ‘Oxford’.