EFFECT OF INSECTICIDE APPLICATION TIMING ON POLLINATOR DIVERSITY IN MUSTARD FIELD BORDERED BY ATTRACTANT CROP

Abstract

The experiment was conducted in the experimental field of Sher-e-Bangla Agricultural University, Dhaka-1207, during November 2019 to February 2020 to find out the optimum time of insecticide application in mustard field to reduce mortality rate of the natural pollinating agents of mustard. The experimental design was a split-plot design with three replicates and two factors Factor A: Main factor; Mustard crop bordered by other crops T 1 - Mustard bordered by Dill (Shova), T 2 - Mustard bordered by Linseed (Neela), T 3 - Mustard bordered by Coriander (BARI Dhonia-1), T 4 - Mustard bordered by Niger and T 5 - Mustard without border crop (Control); Factor B: Second factor; insecticide: Actara 25WG@ (0.3gm/L; at the 15 days intervals) application timing where S 1 - Spray insecticide at 8.30 am, S 2 - Spray insecticide at 11.30 am, S 3 - Spray insecticide at 2.30 pm and S 4 - Spray insecticide at 5.00 pm. Effect of insecticide application time of pollinators was calculated and it was revealed that mustard plants with border crops were greatly influenced by the presence of different pollinators which increase crop yield. Diversity of insect pollinators was observed and among others presence of honey bee was observed as most frequently visited pollinators (33,24). The ShannonWeaver diversity index in mustard field bordered with Niger for species was 1.87,

16.4

% community dominance observed species in mustard field bordered with Niger. Total seed weight/plant of mustard significantly influenced by different pollination conditions with the influence of bordered crops. The highest seed weight/plant (1123 g) was recorded from treatment T 4 - Mustard bordered by Niger. The lowest seed weight/plant (922.70 g) was recorded from treatment T 5 – Mustard without border crop (Control). The optimum time of insect pollinator foraging was observed at 11.30 am and the least number of insect pollinator observed at 5.00 pm, insecticide application should be at 5.00 pm to avoid minimum pollinator drifting. Application of any insecticides at 5.00 pm affect lowest to the insect pollinators population.