Studies on flowering phenology, pollinator diversity, supplemented pollination and their impact on fruit set in apple under changing climatic scenario in Kullu valley of Himachal Pradesh

Pollinators are considered key-stone species in many situations not only because they support humanity but also maintain diversity in ecosystem. Climate change has the potential to alter the phenological synchrony between interacting mutualists such as plants and their pollinators. The data on the impacts of climate change on crop pollination-pollinator interaction are still limited. In the present studies data on apple flowering phenology and weather parameters (average maximum and minimum temperature and rainfall) from 2004 to 2013 have been correlated to visualise the impact of climatic variations on flowering in apple. The data on first flowering date in apple showed that the apple flowering date varied from March 16 to March 29. However when this date of flowering was put to rank correlation with temperature variations showed non-significant trend. Diversity and density of different pollinators viz honey bees, bumble bees, other wild bees, syrphids, drone flies and other insects were recorded using scan sampling and sweep net method which revealed that the diversity of the groups remained same. The investigations also indicated that advancement of flowering in apple did not show any significant impact on population of insect pollinators during these years being 0.67 in 2012 and 1.31 in 2013. The role played by honey bee colonies (Apis mellifera) on fruit set when supplemented to apple orchards has been evaluated. Data on fruit set (on spur basis) at 60 to 200 meter from bee colonies varied between 34.13 and 49.88 per cent and 79.5 and 71.76 per cent in 2012 and 2013 respectively. The data on fruit set irrespective of the year were maximum (59.7) in apple trees near to hive bee colonies while less (31.78) were recorded 200 m away from the bee colonies.