Evaluating Plant Leaf Tinctures against Maize Weevils (Sitophilus zeamais Motsch.) in Stored Maize (Zea mays L.) under Laboratory Conditions

Abstract

Maize weevils (Sitophilus zeamais Motschulsky) are commonly stored grain pests of economic importance in several parts of Africa. A huge amount of synthetic pesticides is being used for the management of crop pests, which have many negative effects on the biotic and abiotic components of the environment. Plant-derived pesticides, on the other hand, are safe for the environment, affect only target insects, have a low application cost, and are easily biodegradable. The purpose of this research was to determine the effectiveness of ethanol leaf tinctures of four selected botanicals against S. zeamais: Brucea antidysenterica (J.) (Waginos), Croton macrostachyus (Hochst.) (broad-leaved croton), Nephrolepis exaltata (L.) (Boston fern), and Carica papaya (L.) (papaya). The experiment was carried out in a completely randomized design (CRD) with four different concentrations (0 mL, 2.5 mL, 5 mL, and 7.5 mL) and four plant leaf tinctures in three replicates. A random sample of 300 g of clean maize seed was treated with the four selected botanicals in plastic jars covered with a muslin cloth. Twenty adult maize weevils were introduced into each disinfected, treated, and untreated maize grain. The mortality rate, grain damage, and F1 progeny emergences were assessed and analyzed using SPSS software version 25. The highest (100%) mortality rate of S. zeamais was recorded for maize seeds treated with the leaf tincture of B. antidysenterica, followed by maize seeds treated with the leaf tincture of C. papaya (97.5%) at an application rate of 7.5 mL/300 g. The mean weight loss of the seeds showed a significant variation between the treatments. The mean weight loss of the seeds in the control (8.96%) was higher than the total mean weight loss treated by all plant leaf tinctures (3.66%). The emergence of F1 progeny of S. zeamais on maize grains showed significant differences among the treatments. The highest emergence (100%) of F1 progenies was recorded for the control treatment followed by C. macrostachyus (16.65%) at a rate of 2.5 mL/300 g maize grain treatment. The study concluded that B. antidysenterica and C. papaya tinctures had the potential to control the infestation of maize grains by S. zeamais.