Host-parasite relations of Bipolaris halodes (Drechs.) Shoemaker on the coconut palm
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2007-02
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The frequent association of leaf rot with the root (wilt) disease resulting in serious decline on the productivity of the coconut palms has been observed in the root (wilt) affected tracts of Kerala. The initial focus of infection is the tender most unopened leaf of the palm and the organism causing the disease has been identified as Bipolaris haldes (Drechs.) Shoemaker. Studies on the preference for tendermost leaves as sites of infection revealed that the thick ness of the epidermal layer of the leaf increased with age, the tendermost leaf having a mean thickness of 6.95 u as against 9.54 u in the matured leaf. The percentage of moisture content was maximum in the tendermost leaf (77.95) and it reduced to 61.33 in matured leaf. Results of tissue analyses indicated higher concentrations of total nitrogen, non-protein and protein nitrogen in the tendermost leaf (2.08 mg/g; 1.71 mg/g; 0.37 mg/g respectively on oven dried basis) and it came down to 1.05 mg/g; 0.87 mg/g and 0.18 mg/g respectively in fully matured leaf. A field experiment conducted to investigate whether proper nutrition ol coconut seedlings with N, P, K, Ca and Mg nutrients could provide any tolerance to infection by B. halodes revealed that although the leaf tissue took up infection, the severity of the same was only minimal in the seedlings receiving treatments of NPK with calcium and magnesium as compared to that in seedlings receiving other treatments. This result also indicates the importance of Ca and Mg nutrition of coconut palms in disease affected tracts.
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Indian Coconut J.1981 v-11 i-11 p-1-4