Abstract

The efficacy of the pre- and post-planting application of neem seed oil (NSO) or/and diazinon and time of harvest for the control of sweetpotato weevil, Cylas puncticollis (Boh.) was evaluated during the 2009 and 2010 cropping seasons. Forty-eight plots of 3 x 4 m² each were demarcated and 240 sweetpotato (var. TIS2532.op.1.13) vine cuttings were dipped into 0, 30 and 50 mls NSO and 30 mls of diazinon mixed in 2 and 10 litre soapy water respectively, and kept for 30 mins before planting. Similar treatment was also basally applied post-planting at 1MAP. In 2009, results showed that treatments (NSO or diazinon or their combinations) did not significantly influence percentage plant stand at harvest in both years, but lower percentage plant stands were obtained at 6 MAP (47.72%) than at 5MAP (56.87%). Significantly higher mean total weights of 34.44 t/ha was obtained in 2009 and 8.99 t/ha in 2010 respectively. Similarly, yield ranged from as high as 53.69 t/ha at 5MAP in 2009 to as low as 5.51t/ha at 6MAP in 2010. Significantly lower C. puncticollis attributes as a pest were obtained in 2009 than in 2010. Treatments significantly suppressed total progeny from 11.07 to 7.08, scores from 3.78 to 2.52 and root damage from 68.59% (Pr0Pt0) to 44.38% (Pr3Pt3), 66.55% to 40.00% at 5 to 6MAP. Time of application was significant as 50 mls of NSO applied pre- and post-planting gave highest (35.30%) control of the pest at harvest.

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