Evaluation of Propiconazole (Tilt) and Pruning in the Control of Black Sigatoka Disease in Ghana

Abstract

Pruning of diseased leaves and the use of Propiconazole (Tilt), a foliar fungicide with systemic properties, were two different recommendations made by the Ministry of Food and Agriculture to control black sigatoka, currently an important disease of plantain in the country. The two methods were evaluated from September 1995 to April 1997 at the University of Ghana Agriculture Research Station, Kade. Four treatments, namely, Tilt (0.125g ai/L), Pruning, Tilt (0.125g ai/L) + Pruning and Control (neither Tilt nor Pruning), were applied in; an RCBD experiment. The average height of the plantain in the different treatments were found not to be significantly different from each other. Using percentage total leaf area attacked, disease severity for the Control treatment was on the average 16% (13.1-19%) while it was 4.6% (2.6- 6.2%),5.1% (3.7-6.4%) and 3.8% (2.5-5.0%) for Tilt, Pruning and Tilt+Pruning respectively. The Control was significantly different from the other three treatments which were, however, not different from each other at 5% significance level. Maturity of plantain was found to delay in the Control. The total number of bunches harvested at 66 weeks were 54, 50, 52 and 47 with bunch weights of 453.OKg, 3 9 2 .2Kg, 405.OKg and 249.lKg for Tilt, Pruning, Tilt+Pruning and Control respectively. The Control was significantly different from the other three treatments which were however not different from each other (p. 5%). The difference in bunch weight was due to significant difference in weight per finger (0.258Kg, 0.245Kg, 0.252Kg and 0.186Kg), respectively, for the treatments. There was no difference in the number of fingers per bunch which was on the average 26.1 for all the treatments. Correlation analysis gave a negative but a significant association (r = -0.96) between severity of disease and yield. Simple pruning and burning of diseased leaves could be recommended for the control of black Sigatoka in the absence of chemical which may be expensive. To determine the potency of the chemical (Tilt), a bioassay was conducted in the laboratory. One ml of the following concentrations of Tilt viz. 0.0125g ai/L; 0.025g ai/L; 0.05g ai/L 0.0625g ai/L and 0.075g ai/L were incorporated into 5 different PDA in Petri dishes to form Tilt-ammended PDA media plus a control (only PDA). Ascospores from diseased leaves were ejected onto these plates. Germination in all cases started about 12 hours after ejection. Unipolar and bipolar germ tubes were observed on all the plates but the percentages differ, depending on the concentration of Tilt. The higher the concentration, the lower the percentage germination. Visible growth was seen with the naked eye after 4 days. Aerial mycelia was whitish with reverse dark on the control plates while the aerial mycelia on Tilt-ammended PDA were gray with reverse dark. No conidia were seen in all cases after several weeks. The bioassay studies confirmed that Tilt was potent.