Coconut Pests and Diseases: Identification, Damage and Practical Management Solutions

1. Major pests of coconut in India

The following pests are important in Indian coconut-growing regions, including Andhra Pradesh, Telangana, Tamil Nadu, Kerala and Karnataka. Their prevalence varies by region and season.

1. Rhinoceros beetle (Oryctes rhinoceros)

Symptoms: Adult beetles bore into the unopened fronds and central crown, leaving characteristic V-shaped cuts on leaves when they unfold. Severe infestation damages the growing point and can weaken or kill young palms.

Chemical control: Axil Placement: Apply Chlorantraniliprole 0.4% GR or Fipronil 0.3% GR at 10–15 g per palm. Mix with equal parts dry sand and place inside the innermost 2–3 leaf axils. Alternatively, place 10–12 g of Naphthalene balls in the topmost axils and cover with sand every 45 days.

Bore Hole Injection: Inject Dimethoate 30% EC or Chlorpyrifos 20% EC directly into active bore holes at the crown base.

Breeding Site Drenching: Spray Carbaryl 50% WP or Malathion 50% EC at 3 g/L of water onto manure pits, compost heaps, and decaying organic matter

Biological control: Apply Metarhizium anisopliae to suitable breeding sites such as decomposing organic matter, and use pheromone traps to monitor and reduce adult beetle populations.

2. Red palm weevil (Rhynchophorus ferrugineus)

Symptoms: Infested palms may show holes in the trunk, oozing brown fluid and chewed plant fibres. In advanced infestations, the crown wilts or collapses, and the palm may die.

Chemical control: To manage red palm weevil, ICAR-CPCRI has described spot application of imidacloprid 17.8% SL or spinosad 45% SC for curative management of infested palms, alongside crown sanitation and removal of breeding sites. 

Biological control: Use pheromone traps for monitoring and mass trapping, inspect palms regularly for early symptoms, and avoid injuries to trunks and leaf bases that provide entry points for the weevil.

3. Black-headed caterpillar (Opisina arenosella)

Symptoms: Larvae feed on leaflets and construct silken galleries containing frass and feeding debris. Damaged leaflets turn brown and dry, reducing the green leaf area and potentially affecting nut production.

Chemical control: 

Foliar Spraying: For younger palms, spray Chlorantraniliprole 18.5% SC at 0.1 mL/L or Malathion 50% EC at 1 mL/L of water to thoroughly wet the lower surface of the fronds.

Root Feeding: For tall, matured palms, drill a downward hole in a functional root, insert a plastic tube, and let the plant absorb Emamectin Benzoate 5% SG or Azadirachtin 5% (50,000 ppm) at 10 mL diluted in 10 mL of water per palm.  

Biological control: Release parasitoids such as Goniozus nephantidis and Bracon brevicornis against larvae, and Elasmus nephantidis against pre-pupal stages. Remove heavily infested outer fronds and conserve natural enemies.
 

4. Coconut eriophyid mite (Aceria guerreronis)

Symptoms: Mites feed beneath the perianth of developing nuts, causing triangular yellow or brown patches near the stalk end. Severe infestation results in scarring, cracking, reduced nut size and premature nut fall.

Chemical control: 

Spot Foliar Spraying: Spray directly onto the innermost 2 to 6 young button bunches. Use Propargite 57% EC at 1.25 mL/L, Fenpyroximate 5% EC at 1 mL/L, or Wettable Sulphur 80% WP at 4 g/L of water.

Root Feeding: For tall palms where spraying is unfeasible, feed via a functional root hole using Fenpyroximate 5% EC at 10 mL mixed with 10 mL of water or Azadirachtin 5% (50,000 ppm) at 7.5 mL mixed with 7.5 mL of water per palm.

Biological control: Use Hirsutella thompsonii, an acaropathogenic fungus studied for coconut mite management. Remove dried flower parts and fallen nuts, and maintain balanced palm nutrition.
 

5. Rugose spiralling whitefly (Aleurodicus rugioperculatus)

Symptoms: Whitefly colonies occur on the undersides of leaflets, where they produce white waxy deposits and honeydew. Black sooty mould develops on honeydew-covered surfaces, reducing the photosynthetic area of the leaves.

Chemical control: To suppress rugose spiralling whitefly, spray neem oil at approximately 0.5% when infestations are severe, ensuring coverage of the undersides of affected leaflets.

Foliar Spraying: Spray the underside of infested fronds using Pyriproxyfen 5% + Diafenthiuron 25% SE at 2 mL/L, Pymetrozine 50% WG at 0.6 g/L, or Acetamiprid 20% SP at 0.5 g/L of water.  

Systemic Treatment: For tall palms, root-feed Dinotefuran 20% SG or Imidacloprid 17.8% SL at 10 mL diluted in 10 mL of water per palm.

Sooty Mould Wash: Spray Wettable Sulphur 80% WP at 4 g/L of water to clear the black sooty mould layers.

• Biological control: Conserve the parasitoid Encarsia guadeloupae and beneficial scavenger beetles. Use water sprays to dislodge whiteflies and install yellow sticky traps for monitoring. 
   

6. Root grub (Leucopholis coneophora)

Symptoms: Grubs feed on roots, causing yellowing, poor growth and reduced nut production. Severely affected palms may show wilting, and root damage can make them less able to withstand dry periods.

Chemical control: To manage root grubs, ICAR-CPCRI has described root-zone drenching with imidacloprid 17.8% SL during periods of grub activity, particularly around the monsoon seasons.

Biological control: Apply neem cake to the palm basin, expose grubs through soil cultivation where practical, collect adult beetles during emergence and use entomopathogenic nematodes.

7. Coreid bug (Paradasynus rostratus)

Symptoms: Bugs feed on developing coconut buttons and young nuts, causing feeding punctures, scarring and premature nut shedding. Damage is particularly important when young bunches are heavily infested.

Chemical control: To reduce coreid bug infestation, apply azadirachtin 10,000 ppm-based botanical insecticide to young coconut bunches during periods of active infestation. 

Biological control: Remove alternate weed and host plants where appropriate, monitor young bunches regularly and conserve natural enemies.

8. Termites (Odontotermes spp.)

Symptoms: Termites damage roots, seedlings and plant tissues close to the soil, particularly in dry or poorly maintained gardens. Infested young palms may show yellowing, wilting and reduced growth.

Chemical control: 

• Soil Drenching (Basin Treatment): For established palms, drench the soil around the palm basin (within a 1-meter radius) using Fipronil 5% SC at 2 mL/L or Imidacloprid 17.8% SL at 1 mL/L of water. 
• Seedling Dipping & Pit Treatment: Before transplanting, dip the root balls of young seedlings into a solution of Chlorpyrifos 20% EC at 3 mL/L of water. Treat the planting pits with Fipronil 0.3% GR at 10–15 g mixed thoroughly with the pit soil.
• Trunk Mud Tube Clearance: Scrape away existing mud galleries from the palm trunk and spray the affected bark surface with Thiamethoxam 25% WG at 0.5 g/L of water to prevent re-infestation.
  
  Biological control: Remove termite-infested debris, maintain suitable soil moisture, use well-decomposed organic manure and protect young palms from severe root stress.

2. Major diseases of coconut in India

1. Bud rot

     

• Causal organism: Phytophthora palmivora.
• Symptoms: The central spindle leaf turns pale, then brown and collapses. The crown may develop a foul smell as the growing bud decays; advanced infection can destroy the growing point and kill the palm.
• Chemical control: To prevent bud rot, apply 1% Bordeaux mixture to the crown before the monsoon period. For early infection, remove decayed tissue and use a suitable copper- or chlorothalonil-based treatment as described in coconut disease management protocols. 
• Biological control: Maintain crown sanitation, remove severely affected tissues, improve drainage and control rhinoceros beetle damage that may facilitate infection.
   

2. Leaf rot

     

• Causal organisms: Colletotrichum gloeosporioides, Exserohilum rostratum and Fusarium solani.
• Symptoms: The spear leaf and young unopened leaves develop brown lesions and decay. Infected leaflets become ragged, dry and discoloured, and severe cases can impair crown development.
• Chemical control: To manage leaf rot, remove infected portions and apply hexaconazole around the base of the spindle leaf as described in ICAR-CPCRI management protocols.
• Biological control: Apply Pseudomonas fluorescens or Bacillus subtilis formulations as preventive treatments, remove infected leaf material and maintain adequate palm nutrition
  

3. Stem bleeding

     

• Causal organism: Thielaviopsis paradoxa (also known as Ceratocystis paradoxa in older literature).
• Symptoms: Reddish-brown fluid oozes from cracks in the trunk, often becoming dark as it dries. The affected tissue beneath the bark decays, and severe infection can weaken the trunk and reduce palm vigour.
• Chemical control: To manage stem bleeding, remove the affected decayed tissue carefully and apply hexaconazole to the treated area. 
• Biological control: Apply Trichoderma harzianum or other effective Trichoderma formulations to treated patches, improve soil drainage and avoid mechanical injury to the trunk.
   

4. Basal stem rot or Thanjavur wilt

• Causal organism: Ganoderma spp., including Ganoderma lucidum in Indian reports.
• Symptoms: Lower leaves yellow and droop, nut production declines, and the lower trunk may show decay. Bracket-like fungal structures may develop near the base of affected palms in advanced cases.
• Chemical control: To manage basal stem rot, hexaconazole root-feeding treatment as part of an integrated management programme, particularly in affected gardens. 
• Biological control: Apply Trichoderma harzianum-enriched neem cake around the palm basin, maintain suitable soil moisture and drainage, and remove severely affected palms when necessary.
   

5. Root wilt disease

• Causal organism: Phytoplasma associated with coconut root wilt disease.
• Symptoms: Leaves become flaccid and bend downward, often showing a characteristic ribbed or flaccid appearance. Palms may exhibit yellowing, reduced nut production and progressive decline over time.
• Chemical control: There is no curative fungicide or insecticide that eliminates the phytoplasma from an infected palm. Management focuses on maintaining palm health and reducing factors that worsen decline.
• Biological control: Maintain balanced nutrition and irrigation, improve soil health, remove severely diseased palms where appropriate and monitor potential insect vectors. Integrated management can improve productivity, but it does not guarantee elimination of the disease.
   

6. Fruit rot and immature nut fall

• Causal organism: Lasiodiplodia theobromae, often associated with mite-damaged nuts.
• Symptoms: Developing nuts develop brown or black lesions and may rot or fall prematurely. Damage may be more severe where eriophyid mite injury provides entry points for secondary pathogens.
• Chemical control: To manage fruit rot associated with Lasiodiplodia, carbendazim or a carbendazim + mancozeb combination can be used  for suppressing the pathogen.  
• Biological control: Reduce eriophyid mite injury, remove diseased and fallen nuts, maintain good garden sanitation and consider garlic bulb extract as a botanical option in organic coconut production.

7. Papery leaf blight

• Causal organism: Pestalotiopsis palmarum (also reported as Pestalotia palmarum).
• Symptoms: Leaflets develop brown lesions that enlarge and dry, leaving pale, papery patches. Severe infection reduces the functional green leaf area and can affect palm vigour.
• Chemical control: To manage papery leaf blight, remove heavily affected leaflets and apply a suitable fungicide such as mancozeb where appropriate for the identified disease.
• Biological control: Remove infected leaf material, improve airflow through proper garden management and maintain balanced palm nutrition.

3. General integrated pest and disease management for coconut

• Inspect the crown, leaf axils, trunk, roots and developing nut bunches regularly.
• Use pheromone traps to monitor red palm weevil and rhinoceros beetle populations.
• Remove infested and diseased plant parts and dispose of them appropriately.
• Use Metarhizium, Trichoderma, Pseudomonas and other validated biological products where appropriate.
• Maintain balanced nutrition, suitable irrigation and good drainage.
• Avoid unnecessary injuries to trunks and leaf bases, which can create entry points for pests and pathogens.
• Diagnose the problem before selecting chemical treatment, particularly for crown rot, stem bleeding and root wilt.