Diversity of Insect Pollinators and Their Impact on the Crop Yield of Mustard (Brassica Campestris L.) in Kusma, Parbat,Nepal

Abstract

Pollination is the most important ecosystem service provided by insects, resulting in sustainability and continuity of the ecosystem. The study was conducted to explore the diversity of insect pollinators and their impact on crop yield of mustard in Kusma, Parbat, Nepal. Four blocks each of size 12 m were establishedby purposive sampling technique considering homogenous and continuous crop cover. Each block had two treatment plots i.e experimental and control plot. Insect diversity was observed in three phases of mustard blooming from 8 hr to 16 hr. Similarly, to find the impact of insect pollination on crop yield, randomly 10 mustard plants from each treatment plots were selected and tagged just before flowering. Finally, all the tagged plants were examined for various qualitative and quantitative parameters. The pollinator insects of mustard included 16 species under five different orders and nine families. Among them, Hymenoptera (36%) was the most abundant order visiting mustard flowers followed by Diptera (34%), Coleoptera (17%), Lepidoptera (12%) and the lowest Heteroptera (1%), whereas Apidae (35.64%) was most abundant family followed by Syrphidae (31.84%). Apis cerana and Eristalis sp. were most important pollinator insects of mustard. Among the recorded 16 species, seven species were found foraging on both pollen and nectar, four species foraging only nectar and remaining five as causal visitors only. The peak foraging activities of most of insects were observed between 12 hr to 14 hr. A significant differences in the abundance of pollinator insects were observed during different phases of flowering (p=0.001). A significant difference was observed in number of branches (4.050±0.171 & 5.025±0.180), number of pods (59.80±1.967 &70.47±2.431), fruit set (70.55±1.362 & 80.94±0.638), number of seeds per pods (16.70±0.248 &19.30±0.330), diameter of seed (0.133±0.2547 & 0.275±0.0051) and weight of 100 dry seeds (0.33±0.058 & 0.48±0.023) respectively in control and experimental plots, whereas, the difference was non- significant in case of height of plant, number of flowers and length of pod between control and experimental plot (p>0.05). Therefore, pollinator friendly cultivation practices should be followed for conservation and management of insect pollinators for higher production and productivity of mustard.