Areca nut, a vital crop in tropical regions, it affected various nutrient deficiencies that significantly impact its growth, yield, and overall health. It has identified the deficiencies early and provided timely intervention and optimal crop management. This blog will discuss the most common diseases that can affect areca nuts, as well as how to manage them.
Mahali or Fruit rot in Arecanut Plants
The disease results in rotting and excessive shedding of immature nuts from the trees during the south-west monsoon. The water soaked dark green or yellowish spots initially develop at the stalk end or base of the nut. The lesions gradually spread, covering the entire nuts, which rot and shed in large numbers. A felt-off white mycelial mass envelopes the entire surface of the fallen nuts. Fruit stalks and rachis of blossoming are also affected. Nuts show large vacuoles and are lighter in weight. Dark brown radial strands on the kernel make them unfit for chewing. Under severe infection, the top of the affected trees dries up, resulting in the withering of leaves and bunches, leading to bud rot symptoms.
management
Adopt clean cultivation. Destroy completely affected trees. Collect and burn fallen nuts. Prophylactic spraying of 1% Bordeaux mixture or copper oxychloride 50 WP (2 gram/liter of water) or copper hydroxide 77 WP (1.5 gram/liter of water) with stickers once before the onset of heavy south-west monsoon and a second and third applications at a 40–45-day interval. Remove and destroy all completely affected inflorescence and immature bunches. In diseased gardens, spray the bunches twice with potassium phosphonate 50 SC (4 ml/liter of water) or metalaxyl + mancozeb 80 WP (2 gram/liter of water) in a 2-week interval, especially during monsoon season. Stem injection or root feeding with 6 ml of potassium phosphonate 50 SC and 5 ml of Tridemorph 80 EC in 100 ml of water is also effective.
Bud rot in Arecanut Plants
The disease results in rotting of the bud portion of the tree. The initial symptom is the discoloration of the spindle leaf from green to yellow and then brown. The base of the spindle leaves rot, which further extends to the growing bud, causing the rotting of the growing bud and the surrounding young leaves of the palm. The affected young leaf whorl and rotted bud portion can be easily pulled off. Infection spread to the adjacent leaves, and these leaves become yellow, droop, and drop off one by one, leaving a bare stem. Rotten buds and spindle leaves emit a foul smell.
management
Remove and destroy dead palms, fruit rot affected bunches, and fallen nuts. When the spindle leaf starts withering, remove and destroy all affected tissues of the spindle along with healthy tissues and apply Bordeaux paste and protect it by covering it with a polythene cover or a mud pot. Drench the spindle leaf base and the base of the other leaves with a 1% Bordeaux mixture or potassium phosphonate 50 SC (4 ml/liter of water) or metalaxyl + mancozeb 80 WP (2 gram/liter of water) in a 2-week interval, especially during the monsoon season. Stem injection or root feeding with 6 ml of potassium phosphonate 50 SC and 5 ml of Tridemorph 80 EC in 100 ml of water is also effective. Keeping a sachet of Metalaxyl + Mancozeb 80 WP or Fosetyl-Al at the base of the spindle leaf is also very effective for the management of this disease.
Inflorescence die back and button shedding in Arecanut Plants
Yellowing of the achillea of inflorescence, which progresses from the tip of the achillea towards the main rachis. Later it became brownish, which soon spread from tip downwards, covering the entire rachis, causing wilting and drying. The female flowers of the infected rachis shed in large numbers, and the whole inflorescence shows a ‘die back’ symptom. The fruiting bodies of the fungus appear as concentric rings in the discolored areas. On severe infection, the female flowers and buttons shed completely, sometimes dry up, and remain on the crown. On incubation, ash colored mycelial growth and pink colored spores of fungus develop from the fallen button and discolored rachis/inflorescence.
management
Remove and destroy completely dried inflorescence, buttons, and all fallen nuts. Spray Bordeaux mixture 1% or Copper oxychloride 50 WP (2.5 gram/liter of water) or Mancozeb 75 WP (3 gram/liter of water) prophylactically just before flowering and also after fruit setting. In diseased gardens, spray Propiconazole 25 EC (1 ml/liter of water) or Hexaconazole 5 EC (1 ml/liter of water), Triadimefon 25 WP (1 gram/liter of water), or Carbendazim 50 WP (1 gram/liter of water).
Foot rot or anabe roga in Arecanut Plants
The leaf lets in the outer wholes of leaves become yellow and droop down, covering the stem. Later, the inner whole leaves also become yellow. Subsequently, all the leaves droop, dry up, and fall off, leaving the stem alone. Then the stem also becomes brittle and easily broken by heavy wind. The base of the stem shows brown discoloration and oozing of dark fluid. Bracket-shaped fructifications of the fungus called ‘anabe’ appear at the base of the trunk. Roots become discolored, brittle, and dried. When an infected trunk is cut, brown discoloration can be seen up to one meter from ground level.
management
Adopt clean cultivation. Distroy infected trees and stumps. Maintain an optimal plant population without overcrowding. Providing good drainage facilities. Apply balanced fertilizers and manures. Dig trenches around the diseased palms to avoid root contact. As a prophylactic measure, apply biocontrol agents Trichoderma harzianum fortified in organic manures into the soil. Drench Bordeaux mixture (1%) or copper oxychloride 50 WP (2.5 gram/liter of water) at frequent intervals. In diseased gardens, drench Propiconazole 25 EC (1 ml/liter of water), Hexaconazole 5 EC (1 ml/liter of water), or Carbendazim 50 WP (1 gram/liter of water) @ 10 liters per palm.
Stem bleeding in Arecanut Plants
Young palms of 10–15 years are more susceptible to the disease. The disease starts as small, discolored depressions or spots on the stem. Spots coalesce to form larger patches, followed by cracking. Fibrous layers of the stem disintegrate, which eventually hollows up to varying depths along the infected portions. Dark brown gummy exudates ooze out from cracks. Stem tapers near the crown. Crown size and yield are reduced. Severely affected palms die off.
management
Improve drainage in the field. Adopt balanced manuring and fertilizer application. Scrape off the affected portion of tissue and burn it. Smear the wound with hot coal tar or rubber Kote mixed with Hexaconazole 5 EC (5 ml/kg of material) or Bordeaux paste.
Yellow leaf disease in Arecanut Plants
Yellowing of tips of leaflets in 2 or 3 leaves of outermost whorl. Brown necrotic streaks run parallel to veins in unfolded leaves. The yellowing extends to the middle of the lamina. Tips of the chlorotic leaves dry up. In the advanced stage, all the leaves become yellow, reduced in size, stiff, pointed, closely bunched/rosetted, and abnormally puckered. Reduction in internodal length, tapering of stem and non-production of inflorescence, shedding of mature and immature nuts in large numbers, and softening and blackening of endosperm are other conspicuous symptoms. Finally, the crown leaves fall off, leaving a bare trunk. Root tips turn black and gradually rot.
management
Maintain trees in good vigor. Growing resistant varieties like true Mangala and South Kanara. Apply potassium and magnesium fertilizers above the recommended level. Maintain soil pH near neutral. Replant the affected gardens with high yielding local varieties like Kasargod local, Dakshin Kannada local, Sirsi local, and Mohit nagar. Apply 100 grams of magnesium and 100 grams of micronutrient food per palm per year. During the early stages of the disease, treat the palms with 500 ppm tetracycline (5 ml/10 liter if water) by spraying and soil drenching. Spray Dimethoate 30 EC (2 ml/liter of water) to control the insect vector.
Leaf rot in Arecanut
Seedling and young bearing palms are mostly affected. Water-soaked lesions on the margins and tips of young leaves and emerging spindle leaves occur and later develop into dark brown sunken spots, which enlarge and dry up due to extensive rotting. Dried and shriveled tips and margins of leaflets shred off, leaving only the mid-veins. Successive infection of an emerging spindle leaf results in the rotting of spindle leaves and growing buds.
management
Remove and destroy the affected portion of the leaves. Spray drenches the inner whorls of leaves and spindle leaf with a Bordeaux mixture (1%) or copper oxychloride 50 WP (2.5 gram/liter of water) or Mancozeb 75 WP (3 gram/liter of water) at monthly intervals. In diseased gardens, spray Propiconazole 25 EC (1 ml/liter of water), Hexaconazole 5 EC (1 ml/liter of water), or Carbendazim 50 WP (1 gram/liter of water) at a fortnightly interval.
Leaf blight in Arecanut Plants
Characteristic reddish brown or dark brown discolored spots on mature outer whorls of the leaves are seen. These spots enlarge to form irregular patches with brown margin and gray center, which have minute black-dot structures and later cause extensive blighting of leaves.
management
Remove and destroy severely affected older leaves; apply the recommended dose of manures and fertilizers; and provide shade to the nursery plants. Spray Bordeaux mixture 1% or Copper oxychloride 50 WP (2.5 gram/liter of water) or Mancozeb 75 WP (3 gram/liter of water) at a monthly interval if the disease is severe.
Leaf spot in Arecanut Plants
Small yellow specks appear on the leaf lamina, which later enlarge to form irregular sunken lesions with dark brown margins and a light brown center having minute dot like structures. A characteristic, prominent yellow halo around the sunken lesions is also very common. Lesions advance and coalesce to form large patches, resulting in premature yellowing, blighting, drying, drooping, and shredding of leaves.
management
Remove and destroy severely affected leaves; provide shade to nursery plants. Spray Bordeaux mixture 1% or Copper oxychloride 50 WP (2.5 gram/liter of water) or Mancozeb 75 WP (3 gram/liter of water) at a monthly interval.
Crown choke in Arecanut Plants
t is a nutritional disorder due to boron deficiency. Leaflets, when unfolding, are crinkled and shorter than normal. In more advanced stages, terminal leaflets remain fused. The tips of these leaflets may be ‘knife-shaped’. This symptom is also called ‘hook-leaf’. Gradually, the spear leaf shortens, and the leaves are reduced to an embryonic midrib without leaflets. This is the so-called ‘little leaf’ stage. Production of barren nuts, nut splitting/cracking, and nut shedding are other symptoms. Boron deficiency is one of the main reasons for this disease.
management
Apply organic manure at the recommended dose of 12 kg per palm per year. Apply borax (2 grams/liter of water) during the early stages to reduce the splitting of nuts. Apply borax at 25-50 grams per palm. Adopt appropriate moisture conservation measures and give adequate irrigation, especially during summer.
Nut -splitting in Arecanut Plants
Nut-splitting is a physiological disorder seen in well grown, young and healthy palms. Premature yellowing of the nuts when they are half to three- fourth mature.
Growth of the pericarp does not keep pace with the development of kernel inside, causing splitting up of the pericarp. Splits develop at the tips, which extend longitudinally exposing the kernel. Cause of the disease is potassium and boron deficiency.
management
Improve drainage in ill drained gardens, Apray borax (2 gram/litre of water) during early stages to reduce splitting of nuts. Apply borax @ 25-50 gram / palm and 25% more of recommended dose of potash fertilizer.
Read more about Arecanut Plant Diseases
