Effects of aqueous and oil leaf extracts of Pterocarpus santalinoides on the maize weevil, Sitophilus zeamais pest of stored maize grains

Abstract

The effects of aqueous and oil leaf extracts of Pterocarpus santalinoides at concentrations of 5, 10, 15 and 20%v/v, each as proctectant in the control of the maize weevil, Sitophilus zeamais, were compared with a conventional insecticide, pirimiphos-methyl at a rate of 0.5 ml / 50 g maize grains of Oba Super II variety in a Completely Randomized Design with four replicates. Parameters assessed, include adult mortality, rate of oviposition and adult emergence, grain damage and weight loss, and seed viability. The data were subjected to analysis of variance and means separated by using Duncan's Multiple Range Test. Mortality of adult S. zeamais increased with increased concentration of the extracts as well as with days of exposure. Emergence rate was significantly (p<0.05) reduced from 41.82% pt in the control values to 19.35 to 2.14% in P. santalinoides aqueous and 9.30 to 0.90% in P. santalinoides oil with pirimiphos methyl having the least number of emerged adults (0.60%). Damaged maize seeds varied from 12.32 to 1.98% in P. santalinoides aqueous extract and 4.86 to 0.61% in P. santalinoides oil extract while 0.59% was recorded in Pirimiphos methyl-treated seed grains. Grain weight loss significantly varied between treatments after two and a half months (F11, 24= 1499.2, p<0.0001). Highest seed germination percentage (78.60%) was observed in seeds treated with 5%v/v P. santalinoides aqueous extract and the control, followed by 72.40% in P. santalinoides oil concentrations at 5, 10 and 15%v/v. The findings showed that almost all treatments except un-treated control decreased (weevil reproduction) grain weight loss and grain damage (holes on grains) in maize.

Effects of biopesticides extracted with a homemade solvent on stored maize protection

“…In an experiment by Asogwa and Osisanya (2003), they compared Cedrela odorata extracts at an extremely low concentration of 8000 ppm to a commonly used stored produce synthetic insecticide and concluded that the botanical extract through topical application caused low adult mortality of only 36%. With 20% v/v of essential oil through a topical application on S. zeamais, Ekeh et al (2018) concluded that there was high mortality, and effectiveness was dependent on dosage and also exposure period which was similar to the results obtained for the plant extracts tested in this experiment.…”

Nano-bioformulations: emerging trends and potential applications in next generation crop protection

“…84 Botanical pesticides also interfere with the synthesis of essential enzymes such as those involved in moulting, hence impeding growth and development. 85 Garlic ( Allium sativum ) and turmeric ( Curcuma longa ) extracts kill, repel, inhibit oviposition, and reduce the appearance of offspring in the red flour beetle ( Tribolium castaneum ). 86 Some botanical pesticides have been linked to insect respiratory system paralysis and inhibition of electron transport, as well as immobilisation and toxicity.…”

An Interesting Relationship between the Insecticidal Potential of Simarouba sp. in the Biology of Diamondback Moth

“…2 and P value F = 19.87; P (> F) < 0.0001 χ 2 = 719.95; χ 2 (> F) < 0.0001Means followed by different letters within a column differed from each other at the 5% significance level. * Data not considered in the analysis because of no variability.…”

“…For years, chemical products have been sought as attractive alternatives for pest control [1,2]. However, in addition to their benefits, many consequences should be considered when applying chemical products: environmental problems, human health concerns, pest resistance, mortality of beneficial insects [3][4][5], toxic residue accumulation, water and soil contamination, toxicity to landholders [6,7], augmentation of secondary pests, pest population explosions, and selection loss of insecticide efficacy [8,9].…”