Abstract
BackgroundAgriculture being one of the major practices in the world has contributed to environmental pollution, especially in developing countries where there were no equipment to recycle the agricultural wastes. Considering the high level of infestation of paddy by Sitotroga cerealella and the high level of pollution caused by agricultural wastes, this research investigated the chemical composition and toxicity of agro wastes (rice husk, maize cob, groundnut and cowpea pods) as eco-friendly protectants of paddy against Sitotroga cerealella. Parameters assessed include adult mortality, oviposition, adult emergence and egg hatchability. Gas chromatography and mass spectrophotometry were used to isolate and characterize the active compounds present in the most effective crude extract.ResultsThe results of the study revealed that all agricultural wastes showed high mortality effect on S. cerealella. Cowpea pod powder was the most toxic to adult paddy moth that caused 33.33%, 36.67%, 46.67%, 50% and 60% mortality of S. cerealella at concentrations 0.1 g, 0.2 g, 0.3 g, 0.4 g and 0.5 g/20 g of paddy grains after 24 h of exposure, respectively. The Cowpea pod, groundnut pod and maize cob extracts caused 100% mortality of S. cerealella at concentration 0.5 ml/20 g of paddy grains after 96 h of exposure, respectively. The lethal concentrations LC50 and LC90 of cowpea pod after 24 h were 0.16 and 0.64 ml which were the lowest of all agro waste extract tested. GC–MS analysis revealed that 19 chemical compounds were present in cowpea pod extract, 9, 12-Octadecadienoic acid (a methyl ester) has the highest percentage total of 39.57% and 4-Pentenal, 2-methylene (0.12%) has the least percentage total.ConclusionAll the observations revealed that cowpea pod was the most effective. The findings also suggested that the selected agricultural wastes have a promising insecticidal potential and can be used as alternatives to synthetic chemical insecticides for the control of stored product insects.
Highlights
Agriculture being one of the major practices in the world has contributed to environmental pollution, especially in developing countries where there were no equipment to recycle the agricultural wastes
Cowpea pod powder was the most toxic to paddy moth that caused 33.33%, 36.67%, 46.67%, 50.00% and 60.00% mortality of S. cerealella at concentrations 0.1 g, 0.2 g, 0.3 g, 0.4 g and 0.5 g/20 g of paddy grains after 24 h of exposure, respectively. This was followed by groundnut pod powder that evoked 30%, 33.33%, 43.33%, 46.67% and 56.67% mortality of paddy moth at concentrations 0.1, 0.2, 0.3, 0.4 and 0.5 g/20 g of paddy grains after 24 h of exposure, respectively
A low adult emergence (30.00) of adult S. cerealella was discovered in paddy treated with rice husk powder at dose 0.1 g/20 g of paddy and its effect compared to the control which was 83.67. This was followed by groundnut pod powder that highly inhibited the development (1.00) of S. cerealella at concentration 0.5 g/20 g of paddy
Summary
Agriculture being one of the major practices in the world has contributed to environmental pollution, especially in developing countries where there were no equipment to recycle the agricultural wastes. Rice production is threatened by a lot of lepidopteran and coleopteran pests (Ashamo and Akinnawonu 2012; Padmasri et al 2017). Stored paddy is susceptible to a large numbers of preand post-harvest pests which cause losses of about 4.09– 12.61% of world paddy production, if not unchecked. Angoumois grain moth (Sitotroga cerealella) is one of the field-to-store lepidopteran pests of paddy in temperate and tropical regions of the world (Adedire 2001; Bushra and Aslam 2014). The moth larvae are the most destructive stage; they enter the grains and feed voraciously on the endosperm which can lead to loss of viability as a result of tunnels made within the paddy (Khattak et al 1996; Tripathi et al 2000; Ileke 2014; Mahmood 2018)
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