Assessing the Effectiveness of Indigenous Plants on Postharvest Pests Control in Rwanda: Case of Tetradenia Riparia and Tephrosia Vogelii on Bean Weevil (Acanthoscelides obtectus)

Abstract

In Rwanda, beans (Phaseolus vulgaris) are important staple crops and constitute the main source of protein, zinc and iron. Acanthoscelides obtectus is a bean weevil, major store pest of beans, caused damages reduce the weight, quality and viability of the seeds. Synthetic pesticides used to control A.obtectus are unfriendly to the environment due to residues. This study was meant to contribute to food security promotion by proposing the use of Tetradenia riparia and Tephrosia vogelii, native species, as botanical alternatives to be used for A.obtectus control. Through this study, ethnobotanical uses of T.riparia and T.vogelii were assessed by the use of semi-structured interviews with local people, to understand their knowledge and perceptions on the pesticidal properties of these plants. A review was carried out to supplement collected information. Plants’dried-leaves powder was used to treat RWV(11-29) variety, reported vulnerable to A.obtectus, data about average damaged grains and weight loss were collected every 2 weeks. Chi-square, ANOVA and Ducan mean separation method were used for statistical analyses. 91% of respondents stated that T.riparia and T.vogelii are used as medicine to treat various ailments. 87% and 53% confirmed to possess some knowledge about the use of T.riparia and T.vogelii respectively in protecting beans against the pest with a treatment period of at least 2 years for T.riparia. Compared to Skana super which is a synthetic pesticide, T.riparia and T.vogelii are less effective; T.riparia is more effective in reducing weight loss where after 4 weeks of treatment T.riparia showed no significant difference from Skana super; 5.48% and 5.20% of weight loss respectively. Further researches and trainings of farmers about the adequate use and handling of botanicals would help in reducing residues in the environment.