Green coffee scale (Coccus viridis) is a common and serious problem. Scales suck the plant sap resulting in reduced growth and crop yield. Sooty mould (a black, loose, sooty-like cover) often develops on leaves. It grows on the sweet exudate from the scales (honeydew) that also attracts ants.
Symptoms
Green oval shaped scales about 2 to 3 mm long. Often found concentrated on leaf veins and tips of new shoots. Infestations then produce spots of honeydew, which become covered with a black sooty mould. Defoliation of badly affected trees can occur.
Control
Preventative:
There are a number of natural predators of coffee scale such as wasps, ladybugs and Verticillium fungus. In many instances, these will reduce the level of scale infestation.
Chemical:
Mineral spraying oils at 200 ml/ 20 L water applied as a spray to affected plants. Only spray if 10 or more leaves are infested with one or more scales. The spray must completely wet and cover the scales. Do not use automotive oil!
Carbaryl 85 % wettable powder at 20 g/10 L water applied as a spray. Apply weekly until scales disappear.
Traditional:
1 kg strong tobacco per 2 L water. Soak for 2 nights. Then remove tobacco. Add 500 g of washing powder and make up to 20 L. Spray weekly until scales disappear.
Scale. Green coffee scale on leaf (top); ants, black sooty mould and scale (centre) and severe infestation on branch (bottom)
Aphids (Toxoptera aurantii) can occur in large numbers on new shoots in the rainy season. Aphids suck sap from young shoots and cause damage to these developing shoots.
Symptoms
Large numbers of small black aphids (2 to 3 mm long) concentrated on new growth. Often associated with black sooty mould.
Control
Generally not warranted.
Chemical:
Neem oil 10 to 20 ml/L, plus soft, finely grated laundry soap at about 7 g/L water.
There are two species of stemborer present in Lao PDR.
Red stemborer (Zeuzera coffeae). The adult has white and black spotted wings. The red coloured larvae tunnel through the coffee branches, normally in the upper part of the coffee trees. Branches and the top part of the main stem easily break off, but the tree usually survives.
White stemborer (Xylotrechus quadripes). The adult is a black and white banded beetle (about 1 to 2 cm long); the head of the male beetle has distinctive raised black ridges. Adults are active during daylight. Damage is caused by the white larvae, which hatch from eggs deposited in cracks and crevices and under loose scaly bark of the main stem and thick primary branches, especially on plants exposed to sunlight. Young larvae feed on the corky tissue just under the bark, which splits making the stem appear ridged. Later, larvae enter the heartwood and tunnel in all directions, even into the roots.
Symptoms
Stemborer damage. Red stemborer (top), white stemborer (centre), general severe damage in a field (bottom)
Wilting of leaves and dead trees or branches. Affected branches are easily broken off. When trees are first infested there maybe evidence of frass (sawdust-like residues) on the ground. The trunk may be ringbarked.
The lifecycle of both pests is completed during the rainy season, but often damage is more evident during the dry season.
Larvae remain inside the tree and are normally not seen. Usually damage is not economically important, although individual trees can be lost.
Control
Preventative:
Less damage occurs under conditions of good shade.
Higher altitude (above 800 m.a.s.l.) seems to reduce the incidence of infestation.
Burn affected trees or branches with borers inside.
Do not plant trees with twisted taproots. These deformed roots result in weak trees that have been shown to have a high incidence of stemborer infestation.
Chemical:
No effective chemical control known. Biological control is not known at this time.
White stem borer. Adult (above) and larva (below)
Red stemborer. Adult moth and larva
Coffee berry borer (Hypothenemus hampei) is a relativity new, but very serious problem in Lao. It is causing significant damage, with perhaps as high as 50% yield loss. The adult is a small black beetle (about 2.5 mm long) and covered in thick hairs. The female beetle bores into berries through the navel region. Cherries are attacked in various stages but tunnelling and laying of about 15 eggs occurs only in hard beans. The eggs hatch in about 10 days and the larvae feed on the beans making small tunnels. Beetles in the cherries either on the plant or on the ground, can survive for more than five months.
Symptoms
Coffee bearer borer. Beetle on a bean (top), damage to berries (centre) beetles (bottom)
Fruit drop of young, green cherries. A small hole is evident on the cherry. Cherries that do not drop often have defective, damaged beans.
Control
Orchard hygiene (keeping the area clean, removing dropped cherries, removing carry-over fruit from coffee bushes are suggested), but it is reported to have limited impact and can be expensive. Cherries on the ground and old berries remaining on the trees are sources of new infection.
There are few natural enemies of the borer. One wasp (Phymastichus coffea) has shown promise in Columbia, but its effectiveness and that of other wasps is not yet fully known. The wasp may make a contribution in an IPM system. Lao should procure this and other effective parasitoids from Cenicafe in Colombia and technical biocontrol support.
Interest is now focused on the commonly found fungus, Beauverai bassiana. Research in South America has shown promising results, but it is not a cheap alternative to chemicals and has to be re-applied.
Research is required to develop the best means of bio-control.
Chemical control is difficult as the borer spends most of its life cycle deep inside the coffee berry. Endosulfan 35 EC at a rate of 6 ml/4.5 L of water applied at early fruit set (2 mm cherry size) and later 120 to 150 days after fruit set if required. Cypermetrin and Deltametrin, pyrethroids (0.01%) at 26 ml/15L of water are an alternative, or Chlorpyrifos used at recommended rate on label.
Quarantine. The pest cannot migrate any distance on its own. Do not allow cherries or coffee bags from other farms onto the farm property. Crop bags should be fumigated before being transported to other coffee growing areas.
Ethyl alcohol and methyl alcohol at a rate of 1:1 is effective in trapping CBB and can be used most effectively at processing/ washing places to prevent re-infestation. Place traps in the first five rows of coffee growing near the processing area.
Coating pieces of plastic with axle grease and engine oil and attaching these to pulpers and machines in the coffee processing area can also be used to capture CBB.
Careful drying of coffee cherry or parchment reduces reproduction of the pest as they cannot survive in coffee beans that are properly dried to 12% moisture.
Coffee berry borer trap. There are many ways to make these simple traps
Mealybugs (Planococcus spp.) are small sucking insects (about 3 mm long) covered with a white mealy wax that feed on young shoots and young roots. There are several species similar in appearance to the naked eye. They are generally more of a problem in the dry season when water is lacking. However, serious infestations of mealybug are often found where there has been use of insecticide sprays, especially highly toxic organo-phosphate sprays. These kill almost all insects, including natural enemies of mealybug.
Mealybug. Large white mealybug a leaf
Mealybug. Cherry infestation
Symptoms
White waxy colonies are usually found on the underside of tender leaves and in soft stem areas around berries. Also, they are found on young roots near the main root, especially where soil is loose around the trunk. Mealybugs are often associated with a heavy infestation of sooty mould.
Control
Biological:
Normally sufficient. In other countries, the most important predator is the mealybug ladybird Cryptolaemus montrouzieri. The adults are reddish brown with black wings and about 4 mm long. A parasitic wasp, Leptmastix dactylopii, is also very effective. Lacewings such as Oligochrysa lutea are also predators of mealybug.
Chemical:
Cryptolaemus montrouzieri. Mealybug ladybird adult feeding on scale
Spray Chlorpyrifos on the soil around the tree to kill ants. Ants disrupt the natural enemies of the mealybug. Malathion and Carbaryl sprays can also be effective. Apply according to label recommendations.
Sooty mould. The black mould is often present with mealybugs
Leaf miner. Leaf is also distorted
Leaf miner (Leucoptera coffeina) is often present, especially in shaded coffee.
Symptoms
Transparent areas in the leaf; larvae are present on the underside of the coffee leaf. Fully-grown larvae are about 6 mm long.
Control
Normally a minor problem with no control warranted.
Termite attack. Dead wood encourages termites to build nests
Termites (Macrotermes spp.) can be a problem on older coffee and shade trees with dead wood where termites breed.
Control
Plant coffee in clean ground where all tree parts, including roots have been removed. Termites cannot survive as there is no dead wood on which to feed.
Effective pruning of dead wood on coffee trees. Remove all dead wood from the coffee plantation.
Permetrin 60 to 80 g/L sprayed on the ground and on base of coffee trees after planting will assist.
A number of diseases can affect coffee plants in the nursery as seedlings, in the field while young and later as bearing trees.
Coffee seedlings are susceptible to two main diseases in the nursery - Damping-off and Cercospora leaf spot (brown eye spot).
Damping off. Note the brown, rotting stems
This disease occurs on young coffee seedlings in the germination bed, after germination and before transplanting. It is caused by a Pythium spp. fungus.
Symptoms
Patches of coffee die quickly. Coffee stem is soft and rotten.
Causes:
Soil borne fungi.
Soil too wet.
Too much shade (insufficient drying of soil).
High planting density (too many plants in a small area).
Control
Preventative:
Don't use old soil from nursery beds or bags as disease is soil borne and can be carried over. Use new soil for nursery beds and potting-up.
Avoid over-watering.
Do not plant seed too close; seeds should be 25 mm apart in rows 100 mm apart.
Chemical control:
Soil drenches of either Benlate (Benomyl) or Captan (Follow label directions as formulations differ).
Seed planting. Do not plant seed too
Close-up. Nursery plants affected with Cercospora
Cercospora leaf spot is a fungus that occurs on leaves when plants are under stress. The fungus can develop both in seedbeds and after plants have been transplanted into bags. It is the most common nursery disease and a sign of poor management.
Symptoms
Brown spots on leaves gradually expanding with reddish brown margin.
Spots on both sides of the leaf.
When there are many spots, leaves appear to have been burnt.
Causes
Soil too wet.
Too much shade or too much sun.
Lack of air movement.
Lack of nitrogen and potassium.
Control
Preventative:
Avoid over-watering.
Maintain 50% shade cover.
Space plant bags to allow air movement.
Proper fertiliser application (refer section on nursery management).
Chemical:
Copper sprays such as the following will give control:
|
Copper Cupravit (85% WP) |
80 g/20 L water |
|
Copper oxychloride |
80 g/20 L water |
|
Copper hydroxide |
40 g/20 L water |
There are several field diseases and disorders affecting leaves and berries. Diseases include Cercospora leaf spot (all ages of coffee); coffee leaf rust (all ages but more on bearing coffee); black sooty mould (all ages) and Anthracnose (more prevalent on bearing coffee). The severe disorder, overbearing dieback, occurs on bearing coffee.
This occurs on the leaf but can also occur on berries where it is known as berry blotch.
Symptoms
Brown spots on leaves gradually expanding with reddish brown margin.
Spots on both sides of the leaf.
Brown sunken lesion on green berries surrounded by a bright red ring (berry blotch).
Causes
Low leaf nitrogen and potassium. Insufficient shade.
Stress from drought, sun exposure, poor fertiliser management, excessive weed competition.
Control
Preventative:
Maintain well-fertilised plants with 50% shade cover.
Chemical:
Should not be needed with good management.
Copper sprays such as the following will give control in severe cases on isolated plants:
|
Copper Cupravit |
(85% WP) |
|
|
80 g/20 L water |
|
Copper oxychloride |
80 g/20 L water |
|
Copper hydroxide |
40 g/20 L water |
Cercospora. Affected berries (top) and leaves (bottom)
Coffee leaf rust (Hemileia vatatrix) occurs on leaves and can cause leaf drop if severe.
Symptoms
The first symptom is the formation of pale yellow spots up to 3 mm in diameter on the underside of the leaves.
As the spots expand, they become powdery and yellow to orange in colour and may reach 20 mm in diameter. Occasionally the whole leaf becomes covered with rust spots.
Older rust spores become brown at the centre surrounded by powdery orange spots.
Leaf drop occurs, which if severe, can lead to dieback and berry loss and a loss of both yield and quality.
Berries tend to be very small, not fully ripe and turn black.
Causes
Variety: Catimor is rust resistant. Java, Typica and many other Arabicas are susceptible under poorly shaded conditions and at altitudes of less than 1000 m.a.s.l.
Plant health: Healthy plants are less susceptible.
Rust spots. Early symptoms (top) and more advanced disease (bottom)
Control
Preventive:
Continued coffee leaf rust
Plant Catimor selections or other more tolerant varieties such as good selections of S 795.
Follow the recommended nutrition programme.
Plant pure Arabica at high elevation only and always use good shade.
Chemical:
Monthly copper sprays (May to October). See label directions for rates.
Leaf rust. Advanced symptom
Sooty mould (Capnodium spp.) develops when the plant is infested with scale, mealybugs, aphids or other sucking insects.
Symptoms
Leaves covered with black, powdery soot.
The fungus grows on honeydew produced by green coffee scale and sucking insects. Ants care for the scales and spread the sooty mould.
Control
Preventative:
Reduce levels of coffee scale, aphids and mealybugs by using recommended control procedures.
Chemical:
Not needed if sucking insects are controlled. Control the insects, not the disease.
Twig dieback. Note the brown stems
Brown blight. Note the brown sunken lesions on berries
Anthracnose (Colletotrichum gloeosporioides Penz.) is a minor flower, twig and cherry disease. It can cause three different coffee diseases - twig dieback, brown blight of ripening cherries and leaf necrosis.
Symptoms
Twig dieback - yellowing and blight of affected leaves. Twigs wilt, defoliate and die at the tips.
Brown blight - brown sunken lesions on fully developed cherries which turn black and hard (can be confused with Cercospora).
Leaf necrosis - round brown necrotic spots up to 25 mm diameter. Worse on sun-burnt or injured leaves.
Control
Maintain healthy coffee plants.
Other control measures are not warranted.
Overbearing. Plant cannot support the extremely heavy crop
Not a true disease but a physiological problem.
Symptoms
Severe leaf loss and branch dieback.
Root dieback.
Cherries ripen prematurely and become hard and black.
Dieback causes alternating bearing (heavy crop one year and poor crop the next).
Plants decline and eventually die if the problem is not corrected in early stages.
Note
Coffee needs one leaf pair to support five to six berries through to maturity.
If there are too many cherries and not enough leaves, all the food goes from the leaf to the developing cherry. Leaves then drop off, causing dieback. Some varieties, especially dwarf Catimors, are more susceptible to this condition. Loss of leaf depletes plant carbohydrate reserves resulting in weakened plants.
Roots also die back, then the tree cannot take up enough nutrients and water, thus more leaves are lost and cherry quality is reduced.
Plant health decline continues and if plants are not well cared for with adequate watering and nutrients, the plants will succumb and die.
Causes
Dieback. Note the dieback in tips and lack of leaves on stems
Dieback. Whole plant affected through the roots; healthy plant (left) diseased
Insufficient nutrition.
Insufficient shade.
Insufficient irrigation.
Variety
Dwarf Catimors are much more susceptible.
Control
Preventative:
Once the problem exists it is very hard to break the cycle if it is left too long.
Maintain good plant health. Maintain good shade (50%). Plant only recommended varieties.
Use a well-balanced fertiliser programme and apply adequate nitrogen and potassium as recommended earlier.
