ABSTRACT
Ten varieties of sweet potato (Ipomoea batatas (L.) Lam) namely: TIS 86/0356, TIS 2532.OP.1.13, TIS 8441, CIP.K.134, Ex-Igbariam, CIP.400004, TIS 87/0087, TIS 8164, CIP Tanzania and Sapele local infected by leafspot disease were screened during 2008 and 2009 cropping seasons to evaluate the foliar spray effect of Asteraceous leaf extract on the tuber yield. The leaf extracts of Synedrella nodiflora, Tithonia diversifolia and Vernonia amygdalina were used and the trials were conducted at the Teaching and Research Farm of Department of Agricultural Education, Delta State University, Abraka. Sweet potato leaves were inoculated using spore suspensions of three fungi (Cochliobolus lunatus, Fusarium lateritium and Fusarium solani) at 85x105cfu/ml 28 days after planting and sprayed at weekly intervals using the extracts and the synthetic fungicide (Dithane M45) in three regimes (once, twice and thrice). Results showed that 5% extract sprays of T. diversifolia, S. nodiflora and V. amygdalina gave a significant (P<0.05) increase in tuber yield compared to the control and dithane M45 across the varieties tested. Tuber yields were higher in Sapele local (24.33 t/ha), TIS 87/0087 (21.67 t/ha), Ex-Igbariam (16.33 t/ha) and TIS 8164 (15.67 t/ha) respectively. For Sapele local and TIS 87/0087, tuber yields were significantly higher P<0.05 than CIP.K.134 (9.00 t/ha) and CIP Tanzania (10.00 t/ha) varieties respectively. Increase in tuber yield due to extract application of T. diversifolia was 6.00 % in CIP Tanzania and 52.85 % in Sapele local. This study therefore recommends: (i) 2 sprays at 7-days interval of 5% extracts of Asteraceae especially that of T. diversifolia be used for field application. (ii) Cultivation of Sapele local, TIS 87/0087, Ex-Igbariam and TIS 8164 varieties is quite promising in this agro-ecological region. |
