Some insects cause high losses of the common bean during storage, namely, <i>Acanthoscelides obtectus</i> Say. Chemical insecticides are commonly used to control insects, but their overuse adversely affects the environment and consumers' health. There is, therefore, the need for an alternative control method. This study was aimed to evaluate the chemical characterization and insecticidal property of <i>Moringa oleifera</i> seed extract on the developmental stages of <i>A. obtectus</i> in stored beans. Three types of <i>M. oleifera</i> seed extracts, namely methanol, ethanol and acetone extracts, were used at doses of 12.5, 25 and 50 µl/ml each. HPLC-MS was used to characterize these extracts. The toxicity of extracts against the adults, the number of eggs and the viability rate of laid or emerged eggs of <i>A. obtectus</i> were evaluated. The results show that <i>M. oleifera</i> seed extract is rich in Hesperidin, Quinic acid, gallic acid, protocatechuic acid, 4-OH benzoic acid, cynaroside, isoquercitrin, cosmosiin, quercitrin, luteolin, naringenin, salicylic acid, Apigenin and Fumaric acid. The acetone extract, from day 2, showed a 100% mortality rate in all doses compared to about only 14% in the control treatment. The number of eggs laid in control (236.67) was higher than the null (0) in acetone treatment at 50 µl/ml. M. oleifera seed extracts contain chemical molecules. They significantly reduced the damage caused by <i>A. obtectus</i> on stored <i>P. vulgaris</i> grains. Therefore, they can be used as an alternative to chemicals for the protection of stored foodstuffs.
In Africa, rice is produced and is a source of food energy in most developing countries. But its cultivation faces to brown spot disease, caused by Bipolaris oryzae (Breda de Haan) Shoemaker, which is a serious seed-borne and seed transmitted disease of rice worldwide.The aim of this study was to screen rice varieties for resistance to brown spot disease in field conditions inYaoundé. A completely randomized Fisher block design with three repetitions was used during 2 growing seasons (2015 and 2016). Growth, yields and disease (incidence and severity) parameters were evaluated on four rice varieties (Nerica 3 and 8, White rice and Kamkou). Results show that height of the Nerica 8 variety (86.03cm) and the number of tillers of Kamkou variety (21.66) were significantly highest compared to others varieties (P<0.05) at 59 Days After Sowing (DAS). There was no significant difference on disease incidence for the different rice varieties at the end of rice plant cycle. However disease severity was lower on Nerica 3(2.71%) and Nerica8 (2.05%) varieties and higher on White variety (4.57%). Hence, Nerica 3 and 8 varieties were more tolerant to brown spot disease than others varieties. Overall, Nerica 3 (3.68 t ha-1) and Kamkou (3.51 t ha-1) varieties resulted in higher yields than white rice 28.93 t ha-1.
Aims: In order to find an alternative to chemical control, the insecticidal potential of aqueous extracts of Thevetia peruviana seeds formulated at 16.66 g/l were tested in the field on the maize stalk borer species. Study Design: The factorial design in subdivided plots or "split-plot" with four replicates and two factors studies was used on an area of 250 m2. Place and Duration of Study: The experiment was carried out in a field located in the city of Yaounde, Cameroon where cassava was grown beforehand, between July and October 2021. Methodology: The extracts at 250 g per 15 l of water were tested against a synthetic insecticide Cypercal at 37.5 ml per 5 l of water and an absolute control (untreated) in a four replicate split-plot device. Two maize varieties (V1: CMS 8704; V2: local) and three treatments (T1: control; T2: T. peruviana seed extract; T3: Cypercal 12 EC) were used. The aqueous extract of T. peruviana was applied by spraying on stems, leaves and leaf cones from 5th to 9th weeks after sowing (SAS). Data were recorded on growth parameters, stem borer density, and maize grain yield. Results: The results show that the application of the treatments resulted in a good development of the growth parameters in the two maize varieties used. Two species of borer Busseola fusca and Sesamia calamistis belonging to the order Lepidoptera were identified. The density of maize stalk borers was significantly reduced (T2: 3 borers) in the subplots treated with aqueous extracts compared to the control (T1: 10 borers). Treatment T2 (2.05 t/ha) gave higher grain yield than the control (1.41 t/ha). Conclusion: The aqueous extracts of T. peruviana seeds having thus shown a strong insect repellent potential in the field can therefore be integrated into the framework of biological control that protects the environment and human health.
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