Browsing by Author "Liyanage, G.W."

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The control of white root disease in Sri Lanka
(Rubber Research Institute. Agalawatta, 1973) Liyanage, G.W.; Peries, O.S.
Investigations on new fungicidal systems for control of bark rot on Hevea brasiliensis
(Rubber Research Institute. Agalawatta, 1977) Liyanage, A. De S.; Nadarajah, M.; Liyanage, G.W.; Dantanarayana, D.M.
The efficacy of Bark Rot fungicides is significantly impared by frequent rains. The present investigation was therefore undertaken to examine the possibility of increasing the efficacy of panel fungicides by incorporating them in rubber latex. Several didithiocarbamates containing metal ions, chemicals such as zinc oxide and formaldehyde and fungicides recommended for Bark Rot control were used singly or in combination, in in vitro trials. Zinc oxide and Zinc dithiocarbamates were of limited use, while others gave satisfactory results. The influence of rubber serum, on the activity of the chemicals and fungicides was then examined. It was shown that all the materials tested except Ziram inhibited te growth of the fungus. Prevulcanised latex was not found to be suitable as an adjuvant under laboratory conditions. However, satisfactory result were obtained when fungicides were incorporated into high ammonia field latex and high and low-ammonia centrifuged latex. The use of preserved latex as an adjuvant with Antimucin and Thiram (TMTD), singly or in combination, was investigated under field conditions. Infection occurred on tapping panels which were inoculateed after removal of scrap, although fungicides were applied prior to inoculation. Disease also occurred on panels, when the inoculum was removed a week after inoculation, but its spread was arrested when fungicides were applied, indicating that continued applications of fungicides could limit the spread of the disease. Panels which were tapped and protected with Antimucin at the time of collection of latex, when inoculated 4 hours later, without removal of scrap, showed less infection. The significance of these findings, in relation to the control of Bark Rot and the influence of these fungicides on the yield are discussed.
Studies on the variability and pathogenicity of Rigidoporus lignosus
(Rubber Research Institute. Agalawatta, 1977) Liyanage, G.W.; Liyanage, A. De S.; Peries, O.S.; Halangoda, L.
White root disease in Hevea, caused by the fungus Rididoporus lignosus (Fomes lignosus) occurs widely in Sri Lanka, In recent years, the severity of the disease has increased alarmingly. One of the factors that could be attributed to the increased incidence of the disease is the virulence of the pathogen. This paper report the results of laboratory experiments on the effects of pH, temperature, light and dark, and relative humidity on a number of isolates, obtained from sites located in different rubber growing areas. The fungus is able to grow over a wide range of temperature with maximum growth being recorded at 30ºC. All the isolates grew better when kept in continuous darkness except one isolate which grew equally well under both light and dark conditions. There was wide variability in the pH requirements for the growth of the fungus. The virulence of the different isolates was examined using healthy rubber roots under laboratory conditions and rubber seedlings in pot culture. The results show that there are differences in virulences and pathogenicity.