Integrated management of leaf rot disease and insect pests on coconut
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Date
2007-02
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Abstract
The loss due to leaf rot disease of coconut was estimated to be 461 million nuts annually in Kerala. A number of fungi have been reported to be associated with the disease of which Exserohilum rostratum and Colletotrichum gleosporoides are important among them. The leaf rot affected spindle is also colonised by mealy bugs, mites and nematodes. Increased incidences of red weevil and rhinoceros beetle are known to occur in leaf rot affected palms compared to the healthy palms in the disease prevalent tracts. In view of the above, an experiment was laid out in farmers garden to study the effect of fungicide and insecticide with nematicidal qualities to study their individual and combined effect in the incidence of leaf rot and pests. Fungicides used were Hexaconazole (Contaf 5 EC - 2 ml), Mancozeb 75% WP (Dithane M-45/Indofil M-45 - 3 g), Phorate (Thimmet 10 G-20 g) and Methyl parathion 2% (Folidol Dust - 50 g). The experiment was continued for four years. There were 8 treatments with 8 replications each and had a completely randomized design. The treatment differences were significant. The palms treated with Mancozeb @ 3 g per palm dissolved in 300 ml water applied twice a year gave maximum reduction in disease indices followed by Phorate + Contaf and Phorate + Indofil and Contaf alone. Superiority of treatment with Indofil M-45 was very clear after each round of observation. At the end of the experiment the average disease index was only 1.0 with 6 out of 8 trees showing no disease symptom. Since rotten portions of the spindle is removed before the application of the fungicide, protection of the wound with an insecticide is a must to save the palms from the incidence of red weevil. Sanitation followed by application of Phorate 20 g mixed with 200 g river sand was better than the application of Folidol dust 50 g in controlling leaf rot which indicated that nematodes have a role in the incidence/aggravation/ transmission of fungi between leaflets of the same spindle or to the next spindle. No additional advantage was seen when Contaf and Indofil were applied together or when Contaf, Indofil and Phorate were applied together. Phorate - 20 g treated palms were totally free from red weevil, rhinoceros beetle, mealy bugs and other insects compared to Folidol Dust - 50 g where stray incidences of rhinoceros beetle infestation occurred. Pouring of 3g Indofil-M45 or contaf 5 EC - 2 ml dissolved in 300ml water after removing rotten portions of the spear leaf followed by application of Phorate 20g mixed in 200g fine river sand to the base of the spindle in April-May and in October-November controlled leaf rot and insect pests on coconut. The coconut water, kernel and oil from mature nuts harvested after 45 days of application of Folidol Dust - 50 g, Contaf- 5 EC - 4 ml and Indofil M-45 - 3 g were free from residues.
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Keywords
coconut, control, leaf rot, insect pests