Pollination Efficiency and Role of Managed Honeybees (Apis mellifera L.) in Yield Response of Canola under Rainfed Conditions

Abstract

Canola (Brassica napus L.) is an important oil seed crop in Pakistan having the potential of bridge gap between consumption and production of edible oil in the country. Canola has high potential of yield but due to many limiting factors, farmers in Pakistan are getting three times less production than developed countries. One of these factors is the insufficient crop pollination. Pollination is an essential ecosystem service andcan be provided by managed pollinators (honeybees and other insects). A two year study was designed to assess the possible role of Apis mellifera managed pollination to enhance the yield of Brassica napus in Gujar Khan, Rawalpindi during 2015 and 2016. Pollen sources of A. mellifera during blooming period of B. napus comprised of 11.11% ornamentals, 33.33% weeds, 22.22% shrubs, 22.22% herbs and 11.11% crops. Quantification of pollens transported by A. mellifera reflected maximum pollens of B. napus followed by Calendula officinalus and Sonchus asper. Studies about determination of colony level pollination efficiency of A. mellifera on B. napus crop depicted that on average maximum colony foraging rate of A. mellifera foragers with pollen loads (281.2 bees/ ten minutes) was observed at 1200 hours on 10-02-2015 (6th weekly interval). Weather factors influenced the activity of A. mellifera colony foraging rate in the field conditions. A. mellifera foragers with pollen loads attained maximum colony foraging activity on 10-02-2015 (6th weekly interval) when the temperature was 21.5 ̊C and average R.H. was 60%. Colony condition of A. mellifera varied throughout the blooming period of B. napus. Maximum brood and stored food area of bees were observed at the end week of B. napus blooming period. xxiv Observations were made about insect pollinators’ visited B. napus throughout the blooming period. Out of thirty five species belonging to five orders and twenty families were recorded. A. mellifera was most frequent visitor comprised 87.66%. Managed A. mellifera had significant effect on yield of B. napus in response to two different treatments. The results about total numbers of pods plant-1, numbers of seeds plant-1 and seed weight pods-100showed significant differences between treatments and revealed that treatment T2 (Open plot free visit of bees+ other pollinators) gave maximum yield as compared to treatment T1 (Cages plants without honeybees). Seed quality parameters of B. napus crop also affected bytwo different treatments (T1=Cages plants without honeybees, T2= Open plot free visit of bees+ other pollinators). Hive distances also affected on colony level pollination efficiency in A. mellifera on B. napus. Colony foraging rate at different hive distances from the B. napus crop proved that colony foraging rate of A.mellifera started to decrease after 200m hives distance. Maximum foraging rate of A. mellifera was at 100m hives distance from B. napus. Effect of beehives distance from B. napus on brood and food stored area of A. mellifera showed that maximum brood and stored food area was found in hives placed at 100m distance from B. napus crop. Overall recommendation for using managed A. mellifera as an important pollinator of B. napus proved that seed yield of B. napus increased with managed pollination of A. mellifera as well as brood and stored food area of A. mellifera also increased with blooming progression of B. napus.