Assessment of Pesticide Usage by Kales Farmers in Kiegoi, the Upper Nyambene Carchement, Meru County, Kenya

Abstract

Pesticides are widely used to protect crops from pests and diseases infestations. However, the use of pesticides in most developing countries poses serious environmental and food safety hazards. These chemicals often leave residues in vegetables post-harvest and may contaminate water sources through runoff and groundwater percolation. Given their intrinsic toxicity, the production, distribution, and use of pesticides require strict regulation and control. This study investigated the commonly used pesticides, analysed pesticides residues in kales samples. A total of 68 respondents were purposively sampled using structured questionnaire. Using a stratified random sampling method, 54 kale samples were collected and analyzed across wet and dry seasons. Samples were packed in labelled zip-lock bags, placed in a cool box, and transported to KEPHIS Analytical Chemistry Laboratory in Nairobi, Kenya where extracts were analyzed using MO301-GC-MS/MS. The Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) protocol was followed for sample preparation and data processed using SPSS version 26. An independent t-test determined statistically significant differences in pesticide residue concentrations in kales and domestic water source between dry and wet seasons and compared to WHO's designated MRLs. The results indicated that 97.1% of farmers use pesticides to protect kale from pests and diseases. The most commonly used pesticides were Dithane M-45 (22.1%), Deltanex (14.7%), Nuvan (11.8%), and Captan 50 WP (11.8%). Other pesticides like Diazinol, Cyperkill, and Trophy each accounted for 7.4%, while Rufast and Roundup made up 4.4% and 1.5%, respectively. (80.9%) reported pesticide applications conducted on a weekly basis with Diazinol, Captan 50 WP, and Dithane M-45 being the most frequently applied pesticide while 16.2% of the respondents reported using Glyphosate (Roundup) on a monthly basis. 85.3% of respondents use diazinol, captan 50 WP and deltanex on their kale crops to combat aphids, leaf spot diseases, and powdery mildew and 5.9%, reported treating maize and potatoes with Dithane M-45 and Roundup. Residue analysis showed Captan concentrations ranged from 0.01533 mg/kg in the wet season to 0.04700 mg/kg in the dry season, showing a statistically significant difference (p=0.001). Deltamethrin residues ranged from 0.01467 mg/kg in the wet season to 0.04200 mg/kg in the dry season, with a significant difference (p=0.000). Diazinon concentrations increased from 0.01567 mg/kg in the wet season to 0.02567 mg/kg in the dry season (p=0.046). Dichlorvos and Diazinon residues exceeded their MRLs of 0.02 mg/kg and 0.01 mg/kg, respectively, while Dieldrin surpassed the WHO MRL of 0.05 mg/kg during the dry season, suggesting a potential food safety hazard. Mancozeb and Deltamethrin concentrations in water were found to be within the WHO MRLs of 0.02 mg/l and 0.5 mg/l, respectively. However, Diazinon and Dieldrin levels exceeded the WHO MRLs of 0.01 mg/l and 0.05 mg/l. According to the WHO classification of pesticides, Dieldrin is a Class 1a pesticide that is extremely hazardous and restricted for use. Cypermethrin, Acetochlor, and Acrinathrin levels were below their respective WHO MRLs of 0.1 mg/l, 0.3 mg/l, and 0.05 mg/l in both seasons.