IMMATURE NUT FALL / FRUIT ROT: Phytophthora palmivora and Lasiodiplodia theobromae
Symptoms
By Phytophthora palmivora:
• Water-soaked lesions start to appear on the nut's surface; • The lesions turn brown and the nut separates from the bunch.
•More frequent in high-humidity regions and during the rainy season.
By Lasiodiplodia theobromae:
• From the apex of the nuts, dark grey to brown lesions with wavy to undulating margins emerge.
• The mesocarp and endosperm of nuts deteriorate and become discolored.
• The early dropping, shrivelling, deformation, and desiccation of nuts.
• Severe infection in nuts contaminated with mites.
• All year round, with a higher frequency in arid regions.
Nut infection and Nut fall by Lasiodiplodia theobromoae.
Management
Effective management of immature nut fall in coconut palms requires a multifaceted approach incorporating physical and chemical methods tailored to the severity of the disease.
Physical Method
To mitigate immature nut fall, it is crucial to remove all rot-affected and dead coconut palms from the orchard before the onset of the monsoon and ensure their proper disposal through burning. This proactive measure helps eliminate potential sources of fungal inoculum and reduces disease pressure within the plantation. By systematically clearing out affected palms, farmers can prevent the spread of pathogens that contribute to immature nut fall, thereby safeguarding the health of remaining coconut palms.
Chemical Method
Chemical interventions are essential for controlling immature nut fall in coconut palms. Crown cleaning just before the monsoon season is crucial to remove any debris or infected plant material that could harbour fungal pathogens. Prophylactic spraying of Bordeaux mixture (1%) or Mancozeb (0.2%) directly onto the bunches should be conducted in two rounds at 30-day intervals, adjusted based on disease severity. This treatment effectively protects developing nuts from fungal infections, thereby reducing premature nut drop.
Additionally, spraying 0.1% carbendazim 50 WP directly onto the bunches of affected palms at 30-day intervals can further suppress fungal growth and enhance fruit retention. This approach targets specific pathogens contributing to immature nut fall and helps maintain yield stability throughout the growing season.
Implementing these integrated disease management strategies ensures comprehensive protection against immature nut fall in coconut palms, promoting healthier growth and sustainable productivity in coconut plantations. Regular monitoring and adjustment of treatments based on disease severity are critical to achieving optimal results and minimizing economic losses due to premature nut drop.
