Detection and distribution of Ceratocystis paradoxa in soil and control of pineapple disease by Benomyl
| MSI00P3399 | |
| Moutia, Y. Doomunkhan, N. Saumtally, S. | |
| Detection and distribution of Ceratocystis paradoxa in soil and control of pineapple disease by Benomyl | |
| 6th ISSCT Sugarcane Pathology Workshop, Thailand, July 16-23, 2000 | |
| Conference paper | |
| 2000 | |
| A semi-selective medium, V8-A, was used for the isolation of Ceratocystis paradoxa from soil. The medium consisted, per litre, of tomato juice or vegetable juice (200ml), calcium carbonate (1.0 g), oxgall powder (1.0 g), pentachloronitrobenzene ( 0.66 g), streptomycin sulphate (0.2 g), tetracycline hydrochloride (0.05 g) and agar (20 g). Plating of various spore concentrations indicated that recovery on the medium was lowered when the concentration was high, possibly due to overcrowding of spores and aggregation. Colonies appeared within two days. The fungus could be recovered on V8-A from artificially inoculated sterile and non-sterile soil at the lowest spore load tested of 62 spores/g of soil. The medium was adopted to determine a qualitative and a quantitative distribution of the pathogen in 61 sugarcane fields from various regions of Mauritius. Twenty-five fields were found infected with spore densities ranging from 14 to 9963/g of soil. The presence of contaminating fungi did not prevent the enumeration of C paradoxa colonies provided that readings were taken within two to three days incubation. The method of isolation on V8-A medium was compared to a qualitative technique by tissue baiting. A tissue plug was removed from the internodal region of a cutting of a susceptible variety (M 261/78) and the whole filled with a soil sample. The development of symptoms together with the presence of typical fungal spores after two weeks were indicative of infection by C paradoxa. The two methods gave comparable results. However, the baiting technique was more sensitive than isolation on V8-A medium. Using the two techniques, the pathogen was detected in all regions of Mauritius, irrespective of soil type and within a wide range of soil pH from 4.2 to 7.9. The relationship between dipping time (15 to 120 seconds) and benomyl concentration (0.2 to 2.2 g/litre) in the control of artificially inoculated pineapple disease was investigated. An inoculum of 4500 spores was applied to each end of the cutting. It was found that the time of contact with the fungicide did not influence the percentage of infected cuttings. In contrast, the concentration of benomyl was important in determining the efficacy of the treatment. At least 1.8 g/litre of benomyl was necessary to control C paradoxa in cuttings under the conditions the experiment was carried out. | |
| 2000-07-28 | |
| En | |
| Mauritius Sugar Industry Research Institute, Réduit, Mauritius University of Mauritius, Réduit, Mauritius | |
| Path |