RRI Publications
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Item Seasonal variations in nodule activity of Pueraria phaseoloides (Roxb) Benth(Rubber Research Institute. Agalawatta, 1990) Jayasinghe, C.K.; Parker, C.A.; Kulasooriya, S.A.The age of Pueraria phaseoloides plants had a marked effect upon the rate of acetylene reduction in their nodules. Acetylene reduction activity increased with the age of the plant and maximum efficiency of nodule activity was detected 60 days after sowing, followed by a marked decline on the 120th day and continued at a low rate. Dry matter yield and total nitrogen in plants was more or less constant thrugh out the assay period.Item Effect of combined nitrogen on growth and nodule function or Pueraria phaseoloides(Rubber Research Institute. Agalawatta, 1991) Jayasinghe, C.K.; Wettasinghe, D.S.Nodulation and nitrogen fixation rates of most of the legumes are reported to be severely affected when they are grown in soils high in available nitrogen. Furthermore, this phenomenon may become more critical when legumes are grown in multiple cropping systems like Pueraria phaseoloides in rubber plantatons where ono legume counterpart is fertilized with nitrogenous fertilizer. Results of experiments conducted in seeding agar to find the effect of nitrogen on growth and nodule function of P. phaseoloides showed that nodulation of P. phaphaeoloides was inhibited at a concentration between 24.4 and 44.8 ppm nitrogenItem Effect of combined nitrogen on nodule function of leguminous crops with special reference to tropical soils(Rubber Research Institute. Agalawatta, 1991) Jayasinghe, C.K.The effect of combined nitrogen on nitrogen fixation has been discussed by several investigators and from their findings it could be concluded that inorganic nitrogen may have either stimulatory, neutral of negative effect on nitrogen fixation depending on the type of legome and soil condition. It was reported in some instances that low levels of combined nitrogen especially when applied as a "Starter" fertilizer at germination, stimulates plant growth and enhances nodule mass and nitrogen fixation. On the other hand when most of the legumes are grown in soil high in available nitrogen, the nitrogen fixation rate is severely affected. This phenomenon may become more critical when legumes are grown as cover crops where non legume counterpart is fertilized with nitrogenous fertilizer. The degree of inhibition appears to vary with sevaral factors vis, concentration of combined nitrogen, host species, cultivar, strain of root nodule bacteria, rate of inculation, light intensity and temperature. However, the most critical factor is the concentration of combined nitrogen and it has been shown that very low concentrations such as 240 ppm N reducedItem Economical and less hazardous fungicide for the management of white root disease(Rubber Research Institute. Agalawatta, 1997) Jayaratne, R.; Jayasinghe, C.K.; Wettasinghe, P.C.Rigidoporus lignosus, the causal agent of white root disease is the most destructive root pathogen of Hevea brasiliensis in Sri Lanka.presently 5-8% of the cultivated lands are affected with this deadly disease and are under bare patches. The recommended fungicides in Sri Lanka,Pentachloro nitrobenzene (PCNB)and Pentachloro phenol (PCP),were prohibited due to high mammalian toxicity and the fungicides of the triazole family which are being recommended in other countries such as Malayasia and Ivory Coast are not acceptable to Sri Lankan rubber growers due to the high costs of these chemicals. The observations of experiments carried out with less toxic chemicals revealed that 8-10% phenol in bituminous base could be used as an effective fungicidal "Collar protectant"in the management of white root disease in Sri Lanka.In this paper the econimics and the toxicological impact on the environment are also discussed.Item Susceptibility of Hevea clones to black stripe disease(Rubber Research Institute. Agalawatta, 1997) Jayasinghe, C.K.; Wettasinghe, D.S.Bark rol or black stripe of Hevea brasiliensis caused by Phytophthora spp.is the only economically important disease of the tapping panel.Screening trials were carried out for three consecutive years at four different localities to evalute the inherent susceptibility of thirty three Hevea clones to black stripe disease.The results indicated that the clones commonly grown in the eastern hemisphere or proved to be potential genetic material for future use show a differential inherent susceptibility with RRIC 130 being the most susceptible.Among the other examined RRIC 119.RRIC 133.RRic 110,RRIC 112,RRIC 114,PB 86,RRIC 117,RRIM 600 and RRIC 132 were susceptible while BPM 24,RRIM 717,RRIC 116,PB 260,RRIC 121 and RRIC 100 were resistant.Item In vitro evaluation of fungicides against rubber isolate of Thanatephorus cucumeris and management of Thanatephorus foot rot of Hevea seedlings(Rubber Research Institute. Agalawatta, 1997) Jayasinghe, C.K.; Fernando, E.B.; Fernando, B.I.Thanatephorus cucumeris, the causal agent of target leaf spot disease of Hevea also attacks the hypocotyls of germinated seeds and cause damping off and foot rot of seedling in Hevea nurseries in Sri Lanka. Sixteen fungicides were screened for their abilities to reduce the saprophytic growth of T.cucumeris on agar and in soil while five fungicides were tested to control foot rot of Hevea seedlings in pots. Five fungicides (benomy 1,Metalaxyl 8% + mancozeb 64%, tebuconazole, thiram and tridemorph) were found to be effective in inhibiting fungal growth 100% (EC 100 %) on agar at a very low concentration of 50 ug/ml. Three fungicides,viz.captan,mancozed,oxadixyl 10% + propineb 56%, pencycuron,propineb and triadimenol) showed EC 100 between 200-800 ug/ml.However,only four fungicides (benomyl,pencycuron,propineb and tebuconazole)reached the EC 100 within the tested range when assessed in the presence of soil indicating that these are the potential fungicides in management of rubber isolate of T.cucumeris. In pot culture trials two fungicides,pencycuron and benomy1 were found to be effective in controlling the disease.However,the disease was completely checked by traditional burning of soil.Item Susceptibility of different leaf stages of Hevea to Corynespora cassiicola(Rubber Research Institute. Agalawatta, 2010) Fernando, T.H.P.S.; Jayasinghe, C.K.; Wijesundera, R.L.C.; Siriwardena, D.Item Penta chloro phenol - effective and economical fungicide for the management of white root disease caused by Rigidoporus lignosus in Sri Lanka(Rubber Research Institute of Sri Lanka. Agalawatte, 1995) Jayasinghe, C.K.; Jayasuriya, K.E.; Fernando, T.H.P.S.Item A comparative study of Colletotrichum species causing anthracnose in Hevea(Rubber Research Institute. Agalawatta, 2009) Jayasinghe, C.K.; Fernando, T.H.P.S.; Jayawardana, N.Item Phytophthora epidemics - possibility of management using resistant clones(Rubber Research Institute of Sri Lanka. Agalawatte, 1996) Jayasinghe, C.K.; Jayaratne, A.H.R.