Management of sweet potato weeviL Cylas puncticollis B. (Coleoptera: Curculionidae) THROUGH earthnig-up and harvesting time and varietal resistance at chano dorga and lante ( arba minch zuria), humb and bale ( wolayita zone) in southern Ethiopia

Abstract

Sweet potato weevil (Cylas puncticollis) B. (Coleoptera: Curculionidae) is the most destructive pest of sweet potato in Ethiopia, particularly in southern part of the country. It causes severe damage by producing bitter taste of tuber which make unsuitable for human consumption and animal feed. This problem necessitated the development of technically sound, environmentally friendly and economically feasible management strategy. Thus, experiments were carried out under field condition of Arbaminch and Wolayta Zone, Southern Ethiopia during the 2011/2012 cropping season from June to December to know the effect of different frequencies of Earthing-up, harvesting time and different varieties of sweet potato on the infestation of sweet potato weevil. The factors were Earthing- up with four levels ( one, two, three times and no earthing –up as control), harvesting times with three levels (prompt harvesting, i.e., immediately when the plant attained physiological maturity, one month and two months delayed harvesting). The experiment was laid out in a randomized complete block design (RCBD) in factorial arrangement with three replications. There were two experiments; one of the experiment was conducted at two locations: Chano Dorga and Lante at Arba Minch Zuria. The other experiment was conducted at two locations of Wolayita Zone: Humbo and Bele. For the second experiment, twenty different varieties of sweet potato were planted in RCBD replicated three times. The variables measured in both cases including marketable and unmarketable yield (t/ha), sweet potato damaged tubers, yield loss, percent damage, root pulling resistant, dry weight, moisture content of sweet potato and sweet potato weevil density. The result obtained indicated that three times Earthing up and prompt harvesting significantly reduced number of damaged tubers per plot (25), SPW per plot ( 29.77), percent damage per plot (6.9 %), unmarketable yield (0.56 t/h) and yield loss (8.68%). This demonstrating that effectiveness of frequent earthing up and prompt harvesting in the management of sweet potato weevil. Among the tested varieties, Kero, TIS.908.7, Mayai, PIPI and Ukerewe were found to be resistant against sweet potato weevil. In this study, interaction effect of earthing up and harvesting time suppress sweet potato weevils’ infestation on sweet potato. Hence, Hence, the use of resistant variety, prompt harvesting and three times earthing up were found effective and recommended in the integrated management of sweet potato weevil in southern Ethiopia.