A study on the stem bleeding disease of coconut in Palakkad district of Kerala

Sem bleeding incidence was high in Eruthempathi, Vadakarapathi, Kozizijampara, Nallepalli, Perumatti, Pattanclreri and Ozhalapathi areas of Palakkad district. On close observation, it was noticed that the number qfpalms with stem bleeding incidence was higher in the plots with waterlogged condition compared to other plots. Stem bleeding incidence was found to be high in palms below the age of 20 years. Percentage ofpalm mortality was high in the case of palms belonging to the age group of 15 ­ 20 years in all places surveyed. Disease index calculated for quantify the disease incidence showed that the attack is moderate with disease index between 2.39 and 8.01. The.palms with more disease index showed low yield. Testing of the soil from stem bleeding affected gardens revealed that all the palms showing the stem bleeding incidence have high content ofP and K. Most ofthe healthy and the stem bleeding affected palms in the disease prone areas have lot ofgrowth cracks on the stem. The pathogen enters through these growth cracks or wounds. The growth cracks may develop after sudden heavy manuring, thrash burning at the: base of the palm or injury made during tractor ploughing etc. cause damage to the palms paving way for infection. Isolation of the causal organism from stem bleeding samples yielded 11 Thielaviopsis paradoxa isolates. Conidia of these isolates were hyaline, cylindrical, apex and base truncate, and thin walled, 7.73 - 5.07 x 3.02 - 4.22 pm formed enterogenously. Chlamydosprores thick walled, brown in chain of4 - 6, remain intact for long time and resembles as multiseptate conidia and ranged from 12.64 - 7.61 x 5.6 - 3.2 pm