Pests and Diseases in Avocado

Avocado is generally a hardy fruit crop, but high humidity, excessive rainfall, poor drainage, dense canopy, and improper field sanitation can increase pest and disease problems. Regular monitoring and timely management are important for maintaining healthy trees and good fruit production.

Major Pests of Avocado

1. Aphids

• Small soft-bodied insects occur on young shoots and leaves.
• They suck plant sap, causing curling and yellowing of leaves.
• Honeydew secretion may encourage sooty mould.
• Heavy infestation can reduce plant growth.

2. Thrips

• Feed on tender leaves, flowers, and young fruits.
• Feeding causes silvery or brown scars.
• Severe damage can affect flowering and fruit development.
• Fruits may develop surface blemishes.

3. Mealybugs

• White, cotton-like insects occur on leaves, shoots, fruits, and branches.
• They suck plant sap and weaken the tree.
• Honeydew can lead to sooty mould.
• Heavy infestation may affect fruit quality.

4. Scale Insects

• Small brown, black, grey, or white scales appear on leaves, branches, and fruits.
• Sap sucking causes yellowing and reduced tree vigour.
• Severe infestation may cause premature leaf drop and drying of branches.

5. Fruit Flies

• Adults lay eggs on developing or ripening fruits.
• Maggots feed inside the fruit.
• Infested fruits may become soft, rotten, and drop prematurely.

6. Mites

• Mites commonly attack leaves, especially under hot and dry conditions.
• Infested leaves may develop yellow or bronze discoloration.
• Severe infestation can cause leaf drop and reduced photosynthesis.

7. Stem and Bark Borers

• Larvae tunnel into branches or trunks.
• Small holes and frass may be visible on affected areas.
• Damaged branches become weak and may dry or break.
• Severe infestation can reduce tree vigour.

Major Diseases of Avocado

1. Phytophthora Root Rot

Phytophthora root rot is one of the most serious diseases of avocado, particularly in poorly drained or waterlogged soils.

Symptoms:

• Leaves become pale, yellow, and smaller than normal.
• New growth becomes weak.
• Roots become brown, damaged, and may decay.
• Severe infection can cause branch dieback and tree decline.

2. Anthracnose

Anthracnose can affect leaves, twigs, flowers, and fruits, particularly under warm and humid conditions.

Symptoms:

• Brown or black spots develop on leaves and fruits.
• Fruit lesions may enlarge and become sunken.
• Infected fruits may develop rot during ripening.
• Severe infection can cause premature fruit drop.

3. Scab

Avocado scab mainly affects young leaves, shoots, and fruits.

Symptoms:

• Small brown or corky lesions appear on fruits.
• Lesions may become rough and raised.
• Severe infection can reduce fruit appearance and market quality.
• Young leaves may show spots and distortion.

4. Verticillium Wilt

Symptoms:

• Leaves may suddenly wilt and droop.
• Branches may show dieback.
• Leaves can turn brown while remaining attached to branches.
• Internal vascular tissues may become discolored.

5. Armillaria Root Rot

Symptoms:

• Trees show gradual decline and reduced growth.
• Leaves may become yellow and wilt.
• Roots become damaged and decayed.
• Severe infection may result in tree death.

6. Stem and Branch Canker

Symptoms:

• Dark or sunken lesions develop on branches or trunks.
• Bark may crack or ooze gum-like material.
• Affected branches may wilt and die back.
• Severe infections can weaken the tree structure.

7. Powdery Mildew

Symptoms:

• White powdery growth appears on young leaves and shoots.
• Leaves may become distorted or curl.
• Severe infection can affect flowering and young fruit development.

Basic Management

• Maintain good drainage and avoid waterlogging.
• Use healthy and disease-free planting material.
• Remove severely infected branches, fruits, and plant debris.
• Maintain proper tree spacing and pruning for good air circulation.
• Avoid unnecessary irrigation and prolonged moisture around the root zone.
• Keep the orchard clean and control weeds.
• Monitor trees regularly for early pest and disease symptoms.
• Use traps for monitoring fruit flies and other pests where appropriate.
• Encourage beneficial insects and natural enemies.
• Disinfect pruning tools between healthy and infected trees.
• Use registered insecticides and fungicides according to the crop label and local agricultural recommendations.

Integrated Pest & Disease Management

1. Use healthy planting material from reliable sources.
2. Select well-drained land and prevent waterlogging.
3. Maintain proper spacing and prune dense branches.
4. Remove infected plant parts and fallen fruits.
5. Maintain good orchard sanitation.
6. Monitor trees regularly, especially during humid and rainy periods.
7. Use appropriate traps for pest monitoring.
8. Encourage natural enemies and beneficial insects.
9. Avoid excessive and unnecessary pesticide applications.
10. Rotate pesticides with different modes of action when chemical control is required.
11. Use only products registered for avocado and the specific target pest or disease, following the label instructions and local recommendations.

Key Point: In avocado, poor drainage, excess moisture, high humidity, weak sanitation, and dense canopy can increase pest and disease problems. Good drainage, orchard hygiene, proper pruning, regular monitoring, and timely management are essential for healthy avocado trees and quality fruit