Browsing by Author "Rasmi, A.R."

Now showing 1 - 11 of 11
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    Bud rot disease An overview
    (2010) Rasmi, A.R.; Rohini Iyer
    Bud rot is a fatal disease of the coconut palm, characterized by the rotting of the terminal bud and surrounding tissues. Even though it affects palms of all ages, young palms in low and moist situations are more susceptible to the disease. Incidence of the disease has been reported from almost all coconut growing countries of the world.
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    Characterization of Phytophthora palmivora isolates inciting bud rot and nut rot in coconut
    (2010) Rasmi, A.R.; Rohini Iyer
    Cultural and morphological characters of 35 isolates of the Phytophthora palmivora collected from rotting bud and nut of coconut were characterized. Basically the colonies were stellate or striate type. Rate of growth in carrot agar varied significantly among the isolates. Rate of growth was fast in Pp22 and Pp23 and slow in isolate Pp14. The sporangia of all the 35 isolates were found to be caducous and were shed with short, broad and occluded pedicel. All isolates of Phytophthora collected in the present study were found to be heterothallic and were of A2 mating type which produced oospores when paired with A1 isolates. Oospore formation in all isolates was noticed only after 15 days of pairing with an A1 isolate. From the above characteristics, all the 35 isolates were confirmed as Phytophthora palmivora Butl. Maximum growth of both bud rot and nut fall isolates of P. palmivora were observed at pH 6.5 (Mean dry weight, 62.36 mg). A temperature range of 25 and 270C supported maximum growth in both nut and bud rot isolates. Among organic Nitrogen sources, glutamine showed maximum dry weight of mycelium both in case of nut fall (58.27 mg) and bud rot isolates (57.00 mg) followed by those supplemented with L-asparagine.
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    Emerging trends in the management of bud rot disease of coconut
    (2004-12) Gunasekaran, M.; Moosa, H.; Rasmi, A.R.; Rohini Iyer; Sheenakumari, T.K.
    In recent times there has been a resurgence of bud rot incidence more or less everywhere in the coconut-growing zones. Though application of Bordeaux mixture is very effective, there are practical difficulties in its implementation. Thesc reasons necessitate the formulation of an alternative IDM strategy for bud rot management. For bud rot management to be effective, a sound forecasting model(s) is an essential one. Considering this, attempts were made to develop forecasting models, based on macro and micro temperature, relative humidity (in plains and hilly areas), and rate of survival of the inoculum in endemic areas during off-season. As an alternative to Bordeaux mixture, systemic fungicides were evaluated: Aureofungin - sol (36.4 g I palm)followed by Calixin (21 ml I palm) as stem injection was found effective. The protection offered against bud rot pathogenby these systemic chemicals extended up to 8 weeks, thus safeguarding the palms during vulnerable period. No residues could be detected in nut water and kernal up to six months after application in the case of Calixin. Hence, the systemics can be administered in advance, well before the onset of the monsoon and there is no need-to climb the tree since the chemical can be administered from the ground. An endophytic bacterium (Bacillus amyloliqriefaciens), a fungus (Trichodernia harzianurn) and botanicals (Andrographispaniculata and Lawsonia inerntis) were found very effective against F palmivora. As these botanicals are not compatible with the antagonist, Z harzianurn sequential application of botanicals and Z har:ianlim by maintaining a suitable interval between the applications is suggested. With the use of standardized ex viva varietal screening technique, a tall cultivar, Laccadive Ordinary (LO) and a dwarf cultivar. Ganga Bondam (GB) were identified as bud rot tolerant varieties. Formulating an IDM strategy combining all the above practices, viz., planting resistant / tolerant varieties, bud rot forecasting based on weather parameters. application of systemic fungicides as prophylactic and application of antagonists (bacterium and fungus) and botanicals for long term sustenance of disease suppression is discussed in this paper.
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    Role of relative humidity and temperature on the survival of Phytophthora palmivora, the incitant of coconut bud rot
    (2004) Rasmi, A.R.; Rohini Iyer; Vijayakumar, K.
    A random survey on bud rot disease of coconut, caused by Phytophthora palmivora, carried out in Kasaragod, Kannur and Calicut districts of Kerala revealed that, there is correlation between the disease incidence and the location of the palms. The disease incidence was high in the hilly tracts (300-1350 MSL), when compared to that of the plains (150 -300 MSL). Studies on the survival off? palmivora propagules in nature revealed that the pathogen survives in the crown of healthy and diseased palms. However, the percentage of survival was high in the endemic areas (Mandapam, Josegiri and Kuttiadi), both in the case of diseased and healthy palms compared to that of areas with lesser disease incidence. Statistical analysis of moisture content I in the debris of crown at different places (CPCRI Kasaragod, Mandapam and Josegiri) during April, July, October and January revealed that differences due to places, season (months) and their interactions are highly significant. Epidemiological observations indicates that macro and micro-temperatures in Mandapam and Josegiri were low, while the micro and macro humidity recorded was high from October-January compared to that of Kasaragod. This shows that the temperature and humidity in the coconut gro\\?ing tracts of hilly areas of Kasaragod, Kannur and Calicut districts are suitable for the survival of the pathogen in the crown during almost all months, resulting in the high frequency of disease incidence during monsoon season and which is also responsible for the continued infection upto January. Examination of the rain water collected from bud-rot affected coconut gardens also indicated that the pathogen surviving in the crown debris can act as a source of inoculum which spreads to the neighboring palms through rain splashes. Based on the above data, it is possible to predict the bud rot incidence well in advance.
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    A study on the Stem bleeding disease of Coconut in Palakkad district of Kerala
    (2010-11) Rasmi, A.R.; Soumya, M.; Nisha, K.
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