INTERNATIONAL JOURNAL OF AGRICULTURE & BIOLOGY 1560–8530/2000/02–4–332–333 1 Polo 500EC (Diafenthiuron), NOVARTIS, Pakistan Limited 2 Pirimor 50DP (Pirimicarb), ICI, Pakistan Limited Insecticidal Mortality, Foraging Behavior and Pollination Role of Honeybee (Apis mellifera L.) on Sarson (Brassica campestris L.) Crop NIGHAT PERVEEN, MUHAMMAD ALHARIRI, MUNIR AHMAD AND ANJUM SUHAIL Department of Agricultural Entomology, University of Agriculture, Faisalabad–38040, Pakistan ABSTRACT Studies were carried out to observe the insecticidal mortality, foraging behavior and pollination role of honeybee (Apis mellifera L.) in sarson, Brassica campestris L. Polo 500EC (Diafenthiuron) and Pirimor 50DP (Pirimicarb) were applied twice @ 617.5 ml/ha with seven days interval at 10-15% blooming period. Maximum bee mortality i.e. 24.67/25 was observed due to Pirimor; whereas, Polo caused 8.67/25 bees mortality 96 h after insecticide treatment. However, in case of Polo, bee mortality decreased gradually to 4/25 and proved safer than that of Pirimor i.e. 10/25, 144 h after treatment. Foragers visited the crop between 8-19 h with most intense visitation between 10-12 h (24.24/flower/10 minutes). The foraging of honeybees resulted in maximum yield, 1000-grain weight and germination percentage of 1990 kg/ha, 3.81 g and 95.8%, respectively. Thus, honeybee foraging caused a significant increase in quantity and quality of sarson crop. Key Words: Apis mellifera L.; Brassica campestris L.; Insecticidal mortality; Foraging; Pollination; Yield; Diafenthiuron; Pirimicarb INTRODUCTION Sarson (Brassica campestris L.) is a rich source of oil and fats in winter crops. There are many reasons for its poor yield in developing countries including the lack of proper pollination that is greatly accomplished by honeybee visitation (Bukheit, 1989). The use of synthetic insecticide may cause alteration in the social behavior of honeybees Apis mellifera L. For instance, an increase in agitation, aggressiveness and pollen contamination in honeybees treated with insecticides (Johansen, 1984). Use of certain insecticides like fenvalerate, phosphomidon, monocrotophos and methamidophos has resulted in delayed foraging (3-4 days) due to the repellant effects to honeybees (Gary & Lorenzen, 1989; Vaidya et al., 1996). The objective of this study was to observe the effect of certain insecticides on honeybees, foraging behaviour and pollination role in Brassica campestris L. for seed yield. MATERIALS AND METHODS Study was conducted at Entomological Research Area, Post Graduate Agricultural Research Station (PARS), University of Agriculture, Faisalabad. The sarson crop was sown on October 15, 1997 on plots (4 × 4 m) and planting geometry was 75 × 30 cm. Three treatments with three replications each, in both experiments, were laid out in RCBD. For toxicological and foraging studies, all three treatments (T1, T2 and T3) were covered with polyethylene sheets. Small beehives were provided in each plot. In each treatment, T1 and T2, two insecticides i.e. Diafenthiuron 1 and Pirimicarb 2 @ 617.5 ml/ha, were sprayed at 10-15% blooming period with seven days interval. Data were recorded before application and after 24, 48, 72, 96 and 120 h of insecticide application. In control (T3), foraging bees were counted from 8 a.m. to 6 p.m. with 10 minutes interval, at alternate days during blooming period. Pollination studies were carried out using the same lay out as described above. In T1, plots were covered with polyethylene sheets provided with small beehives. In T2, plots were sprayed with Pirimor 50DP @ 617.5 ml/ha and then covered with mosquito net bags; whereas, the plots in T3 were left open. Seed yield per hectare, 1000 seed weight and percent germination were recorded and analysed statistically. RESULTS AND DISCUSSION Polo 500EC and Pirimor 50DP @ 617.5 ml/ha each, caused 6/25 and 15/25 bees mortality as compared to that of 3/25 in control 24 h after treatment (Table I). Maximum bee mortality i.e., 24.67/25 was observed due to Pirimor 50DP; whereas, Polo 500EC caused 8.67/25 bee mortality 96 h after insecticide application, respectively. In case of Polo 500EC, it later on decreased gradually. There was a clear decrease in bee mortality i.e. 9.67/25 bees 144 h after Pirimor 50DP as compared to its high mortality for the first four days. However, bee mortality remained lowest and did not exceed above 4/25 in control. Overall results of bee mortality revealed that Polo was relatively safer to honeybee foragers