Control of Callosobruchus maculatus Fabricius (Coleoptera: Chrysomelidae: Bruchinae) using Ethanolic Extracts of Peels from Five Citrus Species
Ethanolic extracts of peels from grape (Citrus paradisi), lemon (C. limon), lime (C. aurantifolia), sweet orange (C. sinensis) and tangerine (Citrus reticulata) were investigated for their insecticidal efficacy against Callosobruchus maculatus Fabricius, a cosmopolitan field-to-storage insect pest of cowpea. The insect was exposed to 3% of each extract admixed with 50 g of cowpea. The setup was a Completely Randomized Design in four replications. Data collected were subjected to analysis of variance and where F-test was significant, means were separated using Student Newman Keul’s test (α = 0.05). Pearson’s correlation analysis was also carried out to show the association between C. maculatus mortality, infestation, seed damage and germination variables. Bioassay results showed significant insecticidal activity of all the tested Citrus peel extracts against C. maculatus life stages and a significant reduction in cowpea seed damage. Adult bruchid mortality caused by the extracts exceeded 90% at 120h post-treatment; with C. limon and C. aurantifolia extracts causing 100% of adult bruchid mortality in the same period. About 62.3-76.4% reduction in the insect’s egg production was observed with the use of the extracts. The perforation index obtained from all the treated seeds was below 50%, and it showed a positive protective potential of the extracts against C. maculatus. The loss in seed weight was significantly lower (<10%) in treated seed compared with the control (>20%). Cowpea seed germination was not impaired by any of the extracts, rather germination increased significantly and seeds treated with C. limon and C. aurantifolia had higher viability (>45.5%) compared with the control. Therefore, ethanolic extracts of peels from the five Citrus species could be a potent pest control option against C. maculatus infestation.
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