Cashew Pests and Diseases: Identification, Impact, and Effective Management Strategies

Introduction

Cashew (Anacardium occidentale) is one of India’s most valuable plantation crops, known for its export potential and high returns. However, its productivity is often threatened by a range of insect pests and diseases that can cause severe yield losses if not managed properly. Adopting an Integrated Pest and Disease Management (IPDM) approach is essential to sustain cashew production and ensure healthy nut quality.

This blog explores the major pests and diseases of cashew, their symptoms, and detailed management practices suitable for both small and large-scale plantations.

MAJOR PESTS OF CASHEW AND THEIR MANAGEMENT

1. Tea Mosquito Bug (Helopeltis antonii)

Nature of Damage:

• The most destructive pest of cashew in India.
• Both nymphs and adults suck sap from young shoots, inflorescences, tender nuts, and apples.
• Affected parts develop brown necrotic lesions, leading to drying and shedding of flowers and immature nuts.

Identification:

• Adult bugs are slender, reddish-brown, with long legs and antennae.

Management:

Cultural: Prune dead and infested twigs to reduce shelter sites.

Mechanical: Install light traps to monitor adult activity.

Chemical:

• Spray lambda-cyhalothrin 5% EC (0.005%), or
• Thiamethoxam 25% WG (0.003%), or
• Imidacloprid 17.8% SL (0.005%) during flushing and flowering stages.

Biological: Encourage natural enemies like Oecophylla smaragdina (weaver ants) and Erythmelus helopeltidis (egg parasitoid).

2. Cashew Stem and Root Borer (Plocaederus ferrugineus)

Nature of Damage:

• Grubs bore into the trunk and root region, forming tunnels filled with frass and gum exudation.
• Severely affected trees show yellowing, wilting, and eventual death.

Identification:

• Adult beetles are reddish-brown and long-horned.

Management:

Cultural:

• Regularly inspect trees for gum exudation and frass holes.
• Remove and destroy infested trees to prevent spread.

Mechanical:

• Chisel out grubs and pupae from tunnels manually.

Chemical:

• Swab basal trunk area with Chlorpyriphos 0.2% or Imidacloprid 0.05%.
• Pour the same solution into holes and plug with mud.

Biological:

• Application of Metarhizium anisopliae or Beauveria bassiana formulations around the root zone for eco-friendly control.

3. Cashew Apple and Nut Borer (Analeptes trifasciata)

Nature of Damage:

• The larvae bore into developing nuts and apples, reducing marketable yield.
• Leads to nut drop and poor kernel quality.

Management:

• Collect and destroy fallen and infested nuts.
• Use pheromone traps to monitor adult activity.
• Spray Spinosad 45% SC (0.015%) or Novaluron 10% EC (0.01%) at early fruit development stage.

4. Thrips (Scirtothrips dorsalis)

Nature of Damage:

• Nymphs and adults suck sap from tender leaves and panicles, causing leaf curling and silvery patches.
• Heavy infestation leads to flower drop.

Management:

• Maintain field sanitation and avoid excess nitrogen fertilizer.
• Spray Fipronil 5% SC (0.01%) or Thiamethoxam 25% WG (0.003%) when thrips population increases.

5. Leaf Miner (Acrocercops syngramma)

Nature of Damage:

• Larvae feed within the leaf tissue forming mines that later turn brown and dry up.
• Reduces photosynthetic area and overall plant vigor.

Management:

• Remove and destroy infested leaves.
• Apply Neem oil 3% or Azadirachtin 1500 ppm @ 5 ml/L as a biopesticide spray.

MAJOR DISEASES OF CASHEW AND THEIR MANAGEMENT

1. Dieback (Colletotrichum gloeosporioides)

Symptoms:

• Young twigs dry back from the tip downward.
• Leaves show brown spots with yellow halos.
• Severe infection leads to complete defoliation and drying of branches.

Management:

• Prune affected branches and burn them.
• Spray Copper oxychloride 0.3% or Carbendazim 0.1% at new flush emergence and repeat at 20-day intervals.

2. Powdery Mildew (Oidium anacardii)

Symptoms:

• White powdery fungal growth on tender leaves, panicles, and young nuts.
• Leads to poor nut setting and flower shedding.

Favorable Conditions:
Cool, dry weather with low humidity.

Management:

• Spray Wettable sulphur 0.3% or Hexaconazole 0.1% at first appearance.
• Avoid excessive shade and ensure good air circulation.

3. Anthracnose (Colletotrichum spp.)

Symptoms:

• Brown or black lesions on leaves, panicles, and fruits.
• Affected nuts show shriveling and premature drop.

Management:

• Remove infected plant debris.
• Spray Mancozeb 0.25% or Carbendazim 0.1% alternately during flowering and fruiting stages.

4. Gummosis (Phytophthora spp.)

Symptoms:

• Gum exudation at the base of the trunk.
• Bark becomes dark and flakes off.
• Leads to wilting and death of branches.

Management:

• Improve field drainage; avoid water stagnation.
• Swab affected areas with Metalaxyl + Mancozeb 0.2% paste.
• Apply Trichoderma viride @ 50 g/tree around the root zone as a biological measure

INTEGRATED PEST AND DISEASE MANAGEMENT (IPDM) IN CASHEW

Field Sanitation:

• Remove fallen leaves, nuts, and dead branches to destroy pest and disease inoculum.

Resistant Varieties:

• Prefer improved cashew varieties like Vengurla-4, VRI-3, and NRCC Sel-2 which show tolerance to major pests and diseases.

Biological Control:

• Encourage beneficial insects, parasitoids, and entomopathogenic fungi.

Monitoring and Trapping:

• Use pheromone traps (for borers), light traps (for moths), and sticky traps (for flying insects).

Judicious Chemical Use:

• Rotate insecticides and fungicides to prevent resistance buildup.
• Follow label recommendations and pre-harvest intervals

Conclusion

Sustainable cashew production depends on the timely identification and integrated management of pests and diseases. By combining cultural, biological, and chemical control measures, farmers can effectively reduce crop losses, improve nut quality, and ensure long-term orchard health.