How to control Pests & Diseases in organic coffee agroforestry

 

Pests and diseases control in organic coffee agroforestry

Coffee is a perennial plantation crop which is often cultivated under agroforestry ecosystem. There are 2 species of coffee; Arabica and Robusta; which are grown under prolong wet weather conditions and invariably suffer from pests and diseases which reduce crop yield and quality. It is therefore important for farmers to identify these pests and diseases at an early stage and take appropriate action to keep plant healthy and prevent crop loss. Arabica coffee is more susceptible to pests and diseases than Robusta coffee. Below are the symptoms and control measures of 15 different coffee pests and diseases which need regular plant protection measures for improved crop production.

1.     Scale  (Coccus viridis)

Green coffee scale is a serious pest. The scale sucks sap from plants and produce honeydew. This encourages growth of sooty mould which reduce leaf area for photosynthesis. Scale infestation could drastically reduce the growth and yield of coffee berries. 

Coffee scale on leaf

Symptoms: A black sooty mould often develops on the leaves and attract ants. They are concentrated on the veins of the leaves and tips of new shoots. The tree can drop it leaves if badly affected.

Control: - Natural predators such as ladybug and wasps will reduce the scale infestation

• Soak 1 kg of tobacco in 2 liter of water for 2 nights. After 2 nights, you remove the tobacco, add 1/2kg of washing powder and fill up to 20 litter. Spray weekly for 4 weeks.
• Mix 200ml of mineral oil in 20L of water. Shake and spray to cover the scales.

2.  Aphids (Toxoptera aurantii)

Coffee Aphid

 Aphids occurs on new shoots often in the raining season. They suck sap from the young shoots and can damage the developing shoots. 

Symptoms: Aphids are often associated with black sooty mould and the large numbers of small black aphids are concentrated on new shoots

Control: - Add neem oil 10ml + liquid soup 2ml in 1L of water, shake well and use to spay aphid.

3.     Stem-borers (red - Zeuzera coffeae & white - Xylotrechus quadripes)

White stem borer

There are 2 types of stem borers – Red and White. The red borer has white and black spotted wings and its larvae tunnel through the top coffee branches causing them to sometimes break off. The white stem-borer is an active black and white banded beetle of about 2cm long. Its larvae are laid in cracks, crevices, loose scaly barks and thick branches. These larvae then enter the heart of the wood and tunnel even right to the roots. 

Symptoms: Stem-borer causes the leaves to wilt and eventually result to dead trees or branches that often breaks off.

Control: - Good shade and higher altitude reduce the incidence of stem-borer infestation

•  Prune and burn affected trees or branches with borers. 
• Avoid planting seedlings with twisted taproots because they develop to week trees that are easily infested by stem-borer.

Red stem borer

• Phyto-sanitary measures -remove any loose barks and thick coffee leaves where eggs are laid
• Frequent pruning and desuckering.
• Spray with 3% neem oil every 2 weeks.
• Apply 10% lime to main stem and thick branches

4   Coffee cherry borer (Hypothenemus hampei)

Coffee cherry borer

Coffee berry borer is a small black beetle (2mm) covered in thick hairs that bores into the berries through the navel region. They borer tunnel and lay eggs in hard beans, the eggs hatch within 10 days and the larvae further feed and tunnel into the beans. 

Symptoms: The young green cherries often drops or are damaged and could result to 50% loss in yield.

Control: - Prune coffee to keep bush as open as possible 

• Good drainage system to create a less humid environment for the beetle       

• Optimal shade to reduce heat – at high temperature the female borer lay more eggs, tunnel deeper and travel fast from berry to berry. 
•  Natural enemies of borer include wasp, Soldier ants, white footed ant and birds which feed on cherry borers especially under shade
• Neem oil spray repels (80%) and kills (65%) borer. Also try Eucalyptus oil
•  Leucaena Leucocephala
• Phyto-sanitation and hygiene - complete harvest, pick and burn all fallen berries
• Use alcohol such as ethyl alcohol and methyl alcohol (1:1) to trap borers 
• Quarantine infested cherries
• Dry of cherry to 12% moisture levels
• Use traps for adult borers
•  Release of parasitoid Cephalonomia stephanoderis in field, post-harvest to reduce  any inoculation over crop residues

5   Mealybug (Planococcus spp )

Coffee mealybug

Mealybugs are small sucking insects (3mm long) that are covered with a white mealy wax and feed on young shoots and roots. Serious infestation occurs where insecticides have been used before to kill all natural enemies of mealybug, especially in the dry season. 

Symptoms: White waxy colonies on underside of tender leaves, young shoots and around berries. Its often occurs together with heavy infestation of black sooty mould.

 Control:  - Ladybird, parasitic wasp and lacewings are very effective predators of mealybug.

• Neem oil (3%) spray is effective against mealy bugs and other sucking pest
• Maintain Proper shade management
• Circle root area with neem oil solution

6     Leaf miner (Leucoptera coffeina)

Coffee leaf miner

Leave miner is common with shaded coffee plantation 

Symptoms: Transparent areas in leaf with larvae (6mm long) under the leaf.

Control: None needed

7.    Termites: Make sure you remove dead woods from coffee plantation so ants don’t feed on it.

***Diseases: Coffee diseases affect plants in nursery as well as on the plantation. Coffee nursery are susceptible to Damping-off and brown leaf spot (cercospora leaf spot). Coffee plantation diseases include Cercospora leaf spot, coffee leaf rust, black sooty mould and Anthracnose (on bearing coffee trees) which often leads to overbearing dieback.

8.     Seedlings: damping-off (Pythium spp.)

Soft rotten stem

This is a fungus that attacks young seedlings after germination. It is cause by soil fungus, wet soil, high planting density and insufficient drying of soil due to much shade cover.

Symptoms: Soft and rotten coffee stem 

Control: - Always use new soil for nursery bed or pots

• Don’t water too m
• Plant seeds about 10cm apart – not too close

9.     Brown eye spot

Brown eye spot

 Cercospora leaf spot is a common nursery disease that occurs when the seedlings are stress out due to poor management. It is often cause by wet soil, poor air circulation, much shade cover and inadequate nitrogen and potassium. 

 Symptoms: Brown spot on leaves which appears as patches of burnt leave.

 Control: - Avoid much watering, maintain below 50% shade cover, 

•   Space seedlings to allow air circulation.

10.  Cercospora 

Berry blotch

This is cause by insufficient shade, inadequate leave nitrogen and potassium, excessive weed, and stress from drought and sun exposure.

Symptoms:  -  It appears as brown eye spot on leaves and sometimes on berries as berry blotch.

• Dark brown, sunken, necrotic spot on berries

Control: - Maintain 50% shade cover 

• Avoid sun scorching on berries and mulch
• Spray the developing berries with 1.0% Bordeaux mixture

 11.  Coffee leaf rust (Hemileia vastatrix)

Arabica coffee is susceptible to leaf rust especially in poorly shaded conditions and lower altitude. The leaf often drops off in severe conditions. The Catimor variety is more resistant to leaf rust.

Symptoms:

Coffee leaf rust

Pale yellow spot on leaves that expand into a powdery yellow to orange circle of about 2cm in diameter. Older rust spores become brown at the center, the leaf drops-off, dieback sets in and yield are drastically reduced. The berries become small, unripe and turn black.

Control: - Increase soil health by enhancing soil organic matter.

• Maintain 50% shade cover,
• Plant Arabica coffee only at high altitude of more than 1000m above sea leves
• Plant rust tolerant variety such as Catimor,
• Regular pruning of infested area
• Monthly spray of Bordeaux mixture (0.5%) from March to October. Especially before the flowers blossom and also in die-back areas.

12.  Sooty mould - (Capnodium spp.)

Coffee sooty mould

 The fungus appears when the plant is infested by pest such as scale, mealybugs and aphids. Ants care for the scales and further spread the sooty mould as they move around.

Symptoms: Black soot powder on leaf.

Control: - Control the pests and the disease will disappear.

• Spray plants with 1kg fish oil resin soap + 1kg starch in 200 litres of water

 13.  Anthracnose (Colletotrichum gloeosporioides Penz.)

It often occurs during dry season and affects leaves, twigs and cherries; causing leave necrosis, twig die-back and beans brown blight.

Dark brown sunken spots

Symptoms: - Leaf necrosis – round dark brown spots which become sever during hot sun burnt 

• Twig die-back – yellowing of affected leaf area, twig wilt, defoliate and the tips die off
• Brown blight – Dark sunken lesion on cherries

Control: - Maintain healthy soil

• Prune affected plants in March
• Maintain overhead shade and mulch plant
• Protect plants by spraying 0.5% Bordeaux mixture in March, May and October

 14.  Overbearing or dieback

Coffee overbearing or dieback

This is actually a physiological problem and not a disease. So many cherries develop and all the nutrients move from the leaves to the cherries causing the leaves to fall off and dieback. The plant becomes weak and eventually the roots also dieback resulting to more leaves lost.  Health of the plant reduce and it finally dies out. 

Symptoms: -   Leaf loss, branch & root dieback

• Premature hard black cherries,
• Alternative bearing (one year much cherries, next year few cherries)
• Plants shrinks and die off

Control: -    Maintain 50% shade cover,

• Enhance organic matter for soil and plant health
•  Enhance nitrogen and potassium (nitrogen fixation trees)

15.  Black rot (Koleroga noxia)

This devastating pathogen infects leaves, developing berries and tender roots. They are also host to trees like oranges, pear, fig etc.

Symptoms: Black & rotten leaves, berries and young twigs. White mycelial strand running along the twig, petiole and spread to lower surface of leaf. Defoliation, loss of berries from infected branches and dieback

Control: -    Pruning of blighted twigs and infected berries along with mycelial thread

• Use of resistant varieties
• Biological control with parasitic fungus like Gliocladium spp., Trichoderma spp., Verticillium spp.
• Pruning and reducing shade before rain begins
• Avoid overcrowding and maintain good air circulation
• Prophylactic sprays of Bordeaux mixture (1%) on leaves and developing berries

Coffee black rot

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