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ThesisItem Restricted Impact of neonicotinoids on honey bees (Apis mellifera Linnaeus) in cotton(Punjab Agricultural University, Ludhiana, 2019) Brar, Pushpinder Kaur; Kang, B. K.The impact of neonicotinoids on Apis mellifera Linneaus in cotton was studied w.r.t. toxicity studies, effect of imidacloprid on colony development parameters and bees in the cotton field and determination of residues in cotton flowers, nectariferous tissue, pollen and hive products. The dermal toxicity laboratory tests revealed that thiamethoxam was the most toxic (LD50 = 7 ng µL-1) followed by clothianidin (LD50 = 10 ng µL-1), imidacloprid (LD50 = 12 ng µL-1), dinotefuran (LD50 = 3767 ng µL-1), acetamiprid (3780 ng µL-1) and thiacloprid (4460 ng µL-1). In oral toxicity studies, the LD50 oral (48 hr after feeding) was clothianidin (0.032 ng µL-1) > thiamethoxam (0.309 ng µL-1) > imidacloprid (3.832 ng µL-1) > dinotefuram (5.420 ng µL-1) > acetamiprid (420.00 ng µL-1) > thiacloprid (463.807 ng µL-1). The effect on colony development can be attributed to sub lethal effects affecting the memory and orientation of bees. The foraging activities of the bees were also influenced. To estimate imidacloprid residues in cotton flower, nectariferous tissue, pollen, bee bread and honey, QuEChERS method was modified and validated according to SANTE guidelines. Experiment was conducted at Raja Harindra Singh Seed Farm, Faridkot and Regional Research Station, Bathinda with four treatments: seed treatment (of cotton crop var. LH 2076) with imidacloprid at single and at double the recommended dose, foliar application of imidacloprid 200 SL at flowering stage at single (40 g/ acre) and double the recommended dose (80 g/ acre) and Apis mellifera colonies were placed on the edge of the treated crop. In spray treatments at RHSSF, Fdkt, average initial deposits in flowers were found to be 1.84 and 3.36 mg/kg; 0.22 and 0.56 mg/kg in nectariferous tissue and 0.88 and 1.58 mg/kg in pollen and 0.01 and 0.02 mg/kg after 7 days of foliar treatment in unsealed honey and 0 .01 mg/kg at 15 days and 0.01 mg/kg at 21 days after foliar treatment at recommended and double the recommended dosages, respectively while at RRS Bathinda, the initial deposits were found to be 1.95 and 3.50 mg/kg in flowers; 0.24 and 0.66 mg/kg in nectariferous tissue, 0.96 and 1.49 mg/kg in pollen and in unsealed and sealed honey were below determination level at 15 and 21 days at recommended and double the recommended dosages, respectively. The samples of all the substrates in the seed treated and control plots did not reveal the presence of imidacloprid. The half-life of imidacloprid at recommended dose was 1.18 and 1.17 days in cotton flower, 0.70 and 0.67 days in cotton nectariferous tissue and 0.41 and 0.44 days in cotton pollen at RHSSF, Faridkot and RRS Bathinda, respectively.