The devasting disease known as "bud rot" is becoming more and more of an issue for coconut palms along India's east and west coasts. particularly in hilly parts of southern states like Kerala and Karnataka. Notable epidemics that occurred in the midst of the 1994 and 2013. Southwest monsoons highlight its variable but deadly nature. Significant occurrences have also been reported from other states, notably Andhra Pradesh, Maharashtra, and Goa, particularly from recently established coconut gardens. Young leaves with the disease wilt and become discoloured. Eventually, the bud collapses and the palm dies. As in monsoon seasons, it spreads quickly in humid, rainy environments.
Symptom
Coconut palms of all ages are seriously affected by bud rot, but young palms are especially at risk, especially in the monsoon season. The disease first appears in seedlings with one to two old younger leaves turn yellow. This is quickly followed by the basal leaf tissues quickly decomposing and coming away from the crown. The spindle withers and falls off as the disease worsens. The crown eventually collapses completely and the palm dies as a result of the soft tissues of the crown decomposing into a slimy mass and releasing an unpleasant stench. The first observable sign in adult palms is a palening of the spear leaf, which finally breaks at the base and hangs downward. As the rot spreads downward, it eventually affects the meristem and kills the palm. The nuts on affected palms may still mature despite the severity of the disease.
Etiology
The Phytophthora palmivora fungus causes the disease known as "bud rot." An extended duration of high relative humidity, frequent rainfall, sporadic sunshine hours, and a predominance of cooler temperatures are favourable for the occurrence of bud rot disease. The inoculum for the next season will come from coconut palms that died from the bud rot disease, as Phytophthora propagules can survive in the crown debris of dead palms up to a year. Slugs (a type of snail) (Deroceros spp.) and rainwater both serve as carriers of infectious propagules, which is crucial for dissemination of this disease.
Management
Cultural method
Controlling bud rot in coconut palms is largely dependent on cultural customs. Ensuring proper drainage is crucial in gardens to avoid waterlogging, which worsen the growth of fungi. In order to minimize humidity and encourage air circulation, which in turn lowers the risk of disease spread, proper spacing between palms is to be given. These steps contribute to make the environment less conducive to fungal infections, especially in gardens where bud rot is a problem. cultural practices like adequate nutrition and drainage, and early detection. For sustainable management, biological control agents are also being investigated. Continuous research and farmer awareness are essential to lessen the devastating effects of bud rot on coconut production and livelihoods throughout India, cause economic threat.
Chemical method
Controlling bud rot also requires the use of chemical techniques. All affected tissue in the crown region needs to be carefully removed as soon as symptoms appear. The crown should then be completely submerged in 0.25% copper oxychloride solution. After this treatment, it is essential to apply Bordeaux paste to shield the crown from rain until new shoots appear. Bordeaux paste is made by dissolving 100 grams of quick lime and copper sulphate in 500 ml of water each. As a preventative measure, nearby palms can also be protected by a pre-monsoon spraying of 0.25% Copper oxychloride or 1% Bordeaux mixture. Mancozeb can provide protection for dwarf varieties of palms that are susceptible to copper
As a pre-monsoon precaution, it is crucial to remove infected crown tissues and apply Bordeaux paste, followed by a biannual spraying of 1% Bordeaux mixture in May and September, to further strengthen defences against bud rot. Treating red palm weevil infestations, which frequently occur in conjunction with bud rot, can be accomplished by packing sand (200 g) and Sevidol 8G (25 g) into leaf axils. spraying palms with 0.25% copper oxychloride after the monsoon offers extra defence against bud rot and guarantees thorough management all the way through the palm's growth cycle.
Disease Management
Integrated disease management strategies should be implemented across three distinct seasons, particularly in endemic regions, to effectively combat the disease.
I. Before the onset of the rainy season:
1. Remove all advanced and dead palms affected by the disease.
2. Clean crowns and ensure field hygiene before the monsoon.
3. Address control measures for other pests and diseases.
4. Apply 1% Bordeaux mixture into the innermost leaf axils just before the monsoon season starts (late May).
II. During the rainy season:
1. Periodically apply prophylactic fungicide treatments at two-month intervals.
2. Regularly monitor palms every 15 days for any signs of bud rot.
3. Promptly identify any initial stages of bud rot incidence.
4. Completely remove infected tissues early and apply 10% Bordeaux paste, covering with a polythene sheet to prevent rainwater entry.
III. Post-monsoon:
1. Maintain bi-monthly prophylactic fungicide treatments until the end of December.
2. Continue regular monitoring every 15 days and initiate curative treatments if necessary.
3. Implement Integrated Nutrient Management practices to support palm health.
