Assessment of plant powders as protectants of stored maize grains against maize weevil, Sitophilus zeamais (Motsch). [Coleoptera: Curculionidae]
A laboratory trial was conducted to determine the toxicity of powdered leaves of Siam weed (Chromolaena odorata), Wire weed (Sida acuta), Gmelina (Gmelina arborea) and Spear grass (Imperata cylindrica) at different dosages (0, 2.5, 5.0 and 7.5g) against the maize weevil (Sitophilus zeamais) infestation and their viability was subsequently tested. The plant powders were mixed with 100g of maize and infested with 30 adults (20 females and 10 males) S. zeamais in 200 ml glass vials and kept under ambient conditions (25 - 30°C and 70 - 90% RH) between July and September, 2017. Treatments were arranged in a completely randomized design, and replicated four times at the Department of Zoology and Environmental Biology, Michael Okpara University of Agriculture, Abia State, Umudike, Nigeria. At 1 week after infestation, all adults were sieved out and the setup kept undisturbed for 5 weeks. Results showed that the mean progeny emergence, weight loss, and percentage grain damage by S. zeamais significantly (P ≤ 0.05) decreased with increased dosage of plant powders. Cypermethrin treated grain gave significantly (P ≤ 0.05) lower values than those treated with plant powders in all parameters tested. Significantly (P ≤ 0.05) lower mean progeny emergence (3.0 and 3.5), and grain weight loss (1.1 and 1.30g) was recorded in I. cylindrica and S. acuta, respectively in 7.5g/100g grains compared with (9.3 and 15.0) and (2.9 and 4.3g) in C. odorata and G. arborea, respectively. However, these treatments did not significantly affect seed germination. These findings indicate that the plant powders used could serve as a safer alternative to synthetic insecticides for the control of S. zeamais in stored maize grains.
Keywords: Esa’ma yewangha, Plant powders, Protectants, and Sitophilus zeamais