Browsing by Author "Vineetha, V."

Filter results by typing the first few letters
Now showing 1 - 1 of 1
  • No Thumbnail Available
    Item
    Insecticide tolerance in stingless bee, Tetragonula iridipennis Smith(Hymenoptera: Apidae: Meliponini)
    (Department of Agricultural Entomology, College of Agriculture ,Vellanikkara, 2023-12-08) Vineetha, V.; Mani Chellappan
    Bees are the most ecologically and economically important group of insects. Many cross-pollinated crops rely on bees for pollination services. Among the bees, stingless bees (Apidae: Meliponini) form the largest group with over 50 genera and more than 505 known species. Stingless bees play a prominent role in the pollination of many food crops. They are recognized as viable pollinators in cucurbits due to their remarkable biological traits that make them suitable for supervised pollination. Stingless bees regularly visit a wide range of flowering crops and often encounter various agrochemicals while foraging in agro-ecosystems. Continuous exposure to insecticides in crop ecosystems can lead to insecticide tolerance in bee populations, much like in pestiferous insects. However, the different mechanisms underlying pesticide detoxification in stingless bees have gained little attention so far. In this context, the present study was undertaken with the objectives of assessing the toxicity of different insecticides to stingless bees, detecting insecticide residues in pollen, determining the activity of metabolic enzymes and investigating the role of gut endosymbionts in insecticide detoxification. Purposive surveys were carried out to document the information on insecticide use in cucurbits from four districts of Kerala viz., Malappuram, Palakkad, Thrissur and Ernakulam. Survey among 120 farmers in four districts recorded the use of 26 different insecticides in cucurbits on an average of 5 to 7 sprays per season at an interval of 12 to 15 days. Based on the survey, the most widely used insecticides viz., chlorantraniliprole, thiamethoxam, malathion, flubendiamide and dimethoate were selected for further toxicological bioassays. Toxicological assays were carried out in two populations of stingless bees collected from a feral colony and an agro-ecosystem using a new protocol standardized as part of the study. The results of bioassay showed that stingless bees from the feral colony had low toxicity to chlorantraniliprole (LC50 of 12.53 ppm) followed by flubendiamide (11.50 ppm), dimethoate (5.28 ppm), malathion (1.20 ppm) and thiamethoxam (0.37 ppm). In comparison, the insecticide flubendiamide was least toxic (LC50 of 20.58 ppm) to stingless bees from the agro-ecosystem followed by chlorantraniliprole (15.59 ppm), dimethoate (9.52 ppm), malathion (4.02 ppm) and thiamethoxam (0.78 ppm). A field experiment was conducted to investigate the presence of insecticide residues in bee pollen by raising bitter gourd plants and fixing stingless bee hives in each treatment plot. Insecticides were sprayed onto the treatment plots and bee pollen samples were collected for residue analysis. The LCMS/ MS and GC analysis of pollen samples detected residues of fipronil and chlorantraniliprole at concentrations of 0.596 mg/kg and 0.108 mg/kg, respectively. The biochemical analyses of stingless bees collected from different treatment plots on 0, 1, 3, 5 and 7 days after spraying insecticides revealed that the total protein content in stingless bees ranged between 2.307 mg/ml for bees in the control plot and 2.565 mg/ml in bees from the dimethoate-treated plot. Highest protein concentration was observed on the third day after treatment application. The highest activity of the detoxifying enzyme, carboxyl esterase was observed in bees collected from the dimethoate-treated plot (83.024 μMol min-1 mg protein-1) and the least in bees from the control plot (26.599 μMol min-1 mg protein-1). The production of carboxyl esterase was found to be highest on the 5th day after spraying. The treatment-wise comparison of the detoxifying enzyme, cytochrome P450 in stingless bees revealed that the enzyme activity was significantly higher in bees collected from chlorantraniliprole treated plot (383.960 pMol min-1 mg protein-1) compared to the control (4.926 pMol min-1 mg protein-1). The cytochrome level was significantly higher on 3rd day after spraying of insecticides. Higher glutathione Stransferase (GST) was induced in bees when sprayed with dimethoate (382.206 μMol min-1 mg protein-1), whereas the level of GST in bees in the control plot was very low (3.164 μMol min-1 mg protein-1). The highest GST activity was observed one day after treatment application which differed noticeably among other days. Investigation and comparison of the gut microbiota of stingless bees collected from the forest and agro-ecosystem were done through metagenomic DNA isolation and next-generation sequencing (NGS) technology. The metagenomic sequencing results showed the presence of 103763 microbes belonging to 123 species and 41080 microbes from 272 species in the gut of stingless bees from the forest and agricultural ecosystems respectively. The predominant microbial species recorded in the bee gut of forest ecosystem was Klebsiella sp. (70.26 %) and in agro-ecosystem was Pantoea agglomerans (84.68 %), which are reported to be involved in insecticide degradation followed by chlorantraniliprole (15.59 ppm), dimethoate (9.52 ppm), malathion (4.02 ppm) and thiamethoxam (0.78 ppm). A field experiment was conducted to investigate the presence of insecticide residues in bee pollen by raising bitter gourd plants and fixing stingless bee hives in each treatment plot. Insecticides were sprayed onto the treatment plots and bee pollen samples were collected for residue analysis. The LCMS/ MS and GC analysis of pollen samples detected residues of fipronil and chlorantraniliprole at concentrations of 0.596 mg/kg and 0.108 mg/kg, respectively. The biochemical analyses of stingless bees collected from different treatment plots on 0, 1, 3, 5 and 7 days after spraying insecticides revealed that the total protein content in stingless bees ranged between 2.307 mg/ml for bees in the control plot and 2.565 mg/ml in bees from the dimethoate-treated plot. Highest protein concentration was observed on the third day after treatment application. The highest activity of the detoxifying enzyme, carboxyl esterase was observed in bees collected from the dimethoate-treated plot (83.024 μMol min-1 mg protein-1) and the least in bees from the control plot (26.599 μMol min-1 mg protein-1). The production of carboxyl esterase was found to be highest on the 5th day after spraying. The treatment-wise comparison of the detoxifying enzyme, cytochrome P450 in stingless bees revealed that the enzyme activity was significantly higher in bees collected from chlorantraniliprole treated plot (383.960 pMol min-1 mg protein-1) compared to the control (4.926 pMol min-1 mg protein-1). The cytochrome level was significantly higher on 3rd day after spraying of insecticides. Higher glutathione Stransferase (GST) was induced in bees when sprayed with dimethoate (382.206 μMol min-1 mg protein-1), whereas the level of GST in bees in the control plot was very low (3.164 μMol min-1 mg protein-1). The highest GST activity was observed one day after treatment application which differed noticeably among other days. Investigation and comparison of the gut microbiota of stingless bees collected from the forest and agro-ecosystem were done through metagenomic DNA isolation and next-generation sequencing (NGS) technology. The metagenomic sequencing results showed the presence of 103763 microbes belonging to 123 species and 41080 microbes from 272 species in the gut of stingless bees from the forest and agricultural ecosystems respectively. The predominant microbial species recorded in the bee gut of forest ecosystem was Klebsiella sp. (70.26 %) and in agro-ecosystem was Pantoea agglomerans (84.68 %), which are reported to be involved in insecticide degradation