Supplementary bioactivities of Curcuma longa extracts and parasitoid Anisopteromalus calandrae as a postharvest eco-friendly management tactic against maize weevil, Sitophilus zeamais (Motschulsky) (coleoptera: Curculionidae)

Abstract

This study investigates the bioactivities of C. longa extracts and parasitoid A. calandrae against the maize weevil, a significant pest in tropical and subtropical regions. The experiments were conducted in a completely randomized design with five replications and six concentrations of C. longa in an incubator at 27 ± 3°C with 65 ± 5% R.H. and a photoperiod of 12:12 h (L:D). This study found that concentrations of C. longa, except higher concentrations (2.5 and 3%), had no significant effect on the settlement of A. calandrae adults on treated maize grains. Corn kernels treated with C. longa aqueous extracts at 0.5, 1, 1.5, and 2% concentrations showed no significant effect on parasitoid development and no significant differences compared to the untreated control. No significant (P > 0.05) differences were found when A. calandrae was offered Sitophilus zeamais for parasitization on maize grains treated with 0.5, 1, 1.5, 2, and 2.5% concentrations of C. longa aqueous extracts. Corn kernels treated with C. longa extracts at the evaluated concentrations reduced the populations of S. zeamais by 20.06, 26.87, 35.19, 41.36, 52.97 and 62.54% whereas; treating with C. longa aqueous extracts at 0.5, 1, 1.5, 2, 2.5 and 3% in combination with the release of five pairs of parasitoids per treatment reduced the population of S. zeamais by 64.24, 66.42, 72.71, 80.87, 86.30 and 90.64% respectively. The combination of C. longa extracts at appropriate concentrations and the release of A. calandrae can effectively manage maize weevil in grain storages as an alternative to chemical insecticides.