Green leaves dropping

Green leaves dropping

The three common causes of green leaves dropping are, Panama disease, bacterial corm rot and water stress. Photo shows initial symptoms.

Panama disease (Fusarium wilt)

Biosecurity Alert

Cause: The fungus Fusarium oxysporum f. sp. cubense which is a soil-borne organism. It is spread in water, soil and planting material. It enters the plant through the roots, and blocks the conducting tissue within the plant resulting in wilting, yellowing of leaves, splitting of pseudostem and death of the plant.

Solution: There is no cure for affected plants. Use only approved planting material and do not plant in previously infested areas.

Biosecurity obligation: Panama is a notifiable disease and you must report any suspicious plants. If you suspect Panama disease you must notify Biosecurity Queensland immediately (13 25 23). 

More info:

Bacterial corm rot

Cause: The bacteria Pectobacterium spp (formerly known as Erwinia spp.) are widespread in most soils. Plants that are stressed from heat or lack of water during the dry season can succumb to bacterial invasion during the early part of the wet season. 
Solution: No chemical treatments are available. Ensure adequate moisture levels are maintained during the dry season and provide good drainage during prolonged wet seasons.

Water stress

Cause: Mild water stress during periods of high evaporation. 
Solution: Apply more water during periods of high demand. 

Internal stem discolouration

Internal stem discolouration

Internal discolouration of the pseudostem.

Panama disease (Fusarium wilt)

Biosecurity Alert

Cause: The fungus Fusarium oxysporum f. sp. cubense which is a soil-borne organism. It is spread in water, soil and planting material. It enters the plant through the roots, and blocks the conducting tissue within the plant resulting in wilting, yellowing of leaves, splitting of the pseudostem and death of the plant.
Solution: There is no cure for affected plants. Use only approved planting material and do not plant in previously infested areas.

 

Biosecurity obligation: Panama is a notifiable disease and you must report any suspicious plants. If you suspect Panama disease you must notify Biosecurity Queensland immediately (13 25 23). 

More info:

Moko disease

Biosecurity Alert

Cause: The bacteria Ralstonia solancearum race 2. Moko is a soil-borne disease and is spread with soil, in water, on implements, in planting material and by insects from flower to flower. The infection enters the plant through the roots and spreads through the host, blocking conducting tissue and resulting in plant yellowing, wilting and death. 
Solution: There is no chemical control for Moko. All plants plus an adequate buffer zone around the diseased plants must be destroyed. The area must be quarantined and only non-host plants grown.  

Biosecurity obligation: If you suspect Moko disease you must notify Biosecurity Queensland immediately (13 25 23). 
More info:

Stem shatters

Stem shatters

Image showing splitting of the pseudostem.

Panama disease (Fusarium wilt)

Biosecurity Alert

Cause: The fungus Fusarium oxysporum f. sp. cubense which is a soil-borne organism. It is spread in water, soil and planting material. It enters the plant through the roots, and blocks the conducting tissue within the plant resulting in wilting, yellowing of leaves and death of the plant.
Solution: There is no cure for affected plants. Use only approved planting material and do not plant in previously infested areas.

 

Biosecurity obligation: Panama is a notifiable disease and you must report any suspicious plants. If you suspect Panama disease you must notify Biosecurity Queensland immediately (13 25 23). 

More info:
Photo shows extreme symptoms.

2,4-D damage

Cause: Injection of 2,4-D will kill the plant. Overspray or drift from herbicide application may cause lesser symptoms.  

Solution: Be extremely careful with chemical applications.

Tissue-cultured off-type

Cause: A genetic abnormality that occurs in tissue-cultured plants. 

Solution: Remove affected plants and set additional following suckers on nearby plants.

Banana streak virus

Cause: The banana streak virus (BSV). Symptom expression is sporadic. Symptoms of cucumber mosaic are similar. 

Solution: Do not take planting material from infected plants. Eradicate infected plants where symptoms are observed. Confirm diagnosis by looking for yellow black streaks or flashes on leaves or by laboratory tests. 

Frost

Cause: Frost during the growing season.

Solution: No cure for damaged plants. Slightly damaged plants may grow out of it.

Small and stunted plants

Small and stunted plants

Tissue-cultured off-type

Cause: A genetic abnormality occurring in tissue-cultured plants.

Solution: Remove affected plants and set additional following suckers on nearby plants.
There are several causes of small and stunted plants but two important ones are burrowing nematode and banana weevil borer.

Burrowing nematode

Cause: Severe root damage caused by burrowing nematode affects the plant’s ability to take up water and nutrients from the soil.

Solution: Check a random sample of roots from the whole field to determine if nematodes are the problem and if a nematicide treatment is necessary.  

Banana weevil borer

Cause: Tunnelling by larvae of Cosmopolites sordidus in the corm. Sever infestation reduces plant vigour. 

Solution: Use stem baits (traps) to establish the severity of the infestation. If numbers exceed an average of 4 weevils per trap, treat with appropriate insecticide. Pheromone traps are also available.

Bunchy top

Cause: The banana bunch top virus (BBTV) which is spread on infected planting material and by the banana aphid, Pentalonia nigronervosa. BBTV is not present in tropical Australia, and movement of planting material is controlled by legislation.
Solution: There is no cure for this disease and all infected plants must be eradicated. Outbreaks must be reported to your state primary industry authority. 
More info:

Not enough water/dry conditions

Cause: Insufficient water for plant growth.

Solution: Use water scheduling techniques to supply sufficient water to meet the plant’s requirements.

Plants turn yellow and die

Plants turn yellow and die

Bacterial corm rot

Cause: The bacteria Pectobacterium spp. (formerly known as Erwinia spp.) that are common soil inhabitants. Plants that are stressed during the dry season can succumb to invasion during the wet season. 

Solution: No chemical treatments are available. Ensure adequate moisture levels are maintained during the dry season and provide good drainage during prolonged wet seasons. 
Water-logging after planting can also cause small and stunted plants.

Water-logging

Cause: Not enough oxygen for the roots caused by too much water in the soil from rainfall or irrigation. 

Solution: Avoid planting in areas that are often water-logged and in heavy soils. Install and maintain the drainage system for your plantation. 
Left: early stage showing the yellowing of leaves. Right: late stage after the leaves have dropped.

Panama disease (Fusarium wilt)

Biosecurity Alert

Cause: The fungus Fusarium oxysporum f. sp. cubense which is a soil—borne organism. It is spread in water, soil and planting material. The fungus enters the plant through the roots and blocks the conducting tissue within the plant, resulting in wilting, yellowing of leaves, splitting of pseudostem and death of the plant. There are several “races” of the disease which affect different varieties.

Solution: There is no cure for affected plants. Use only approved planting material and do not plant in previously infested areas.
Biosecurity obligation: Panama is a notifiable disease and you must report any suspicious plants. If you suspect Panama disease you must notify Biosecurity Queensland immediately (13 25 23). 
More info:

Herbicide damage (glyphosate)

Cause: Glyphosate spray drift onto green parts of the plant. The first symptom is yellowing of leaves.

Solution: No cure for damaged plants. Be extremely careful when using glyphosate. 

Plants kink, bend or fall over

Plants kink, bend or fall over

Borrowing nematode (plants fall over)

Cause: Burrowing nematode feeding on roots weakens the plant’s root system.

Solution: Check roots over the whole field to determine if nematodes are the problem and if a nematicide treatment is necessary. Propping or tying string between plants may prevent some losses.

 

Banana weevil borer (plants fall over)

Cause: Tunnelling by larvae of Cosmopolites sordidus in the corm. Sever infestation reduces plant vigour. 

Solution: Use stem baits (traps) to establish the severity of the infestation. If numbers exceed an average of four weevils per trap, treat with appropriate insecticide. Pheromone traps are also available.

 
Note the trees in the background have been tied or propped.

Poor tying (plants bend or kink)

Cause: Incorrect bunch and tree support.

Solution: Ensure tying or propping is done correctly.

 

Heat stress/lack of water (plants bend or kink)

Cause: Extreme heat and or dry conditions.

Solution: Use water scheduling techniques to supply sufficient water to meet the plants’ requirements.

 

Fruit rotting after harvest

Fruit rotting after harvest

Anthracnose

Cause: The fungus Colletotrichum musae. Spores are produced on dead banana material and are spread to young fruit in water droplets. The fungus remains dormant in the tissue until the onset of ripening.

Solution: Handle harvested banana fruit with care to avoid damage. Apply appropriate post-harvest fungicide treatment.

 

Fungal growth seen on the cut surface of the crown.
Rot extending beyond crown and into fruit.

Crown rot

Cause: Several organisms can be responsible for causing crown rot symptoms. These include Musicillium theobromae, Fusarium equiseti-incarnatum (species complex), Colletotrichum musae and Thielaviopsis musarum. Symptoms can vary from fungal growth ‘fluff’ present on the cut crown surface through to complete breakdown of fruit.

Solution: Application of appropriate post-harvest fungicides will assist in minimising symptoms in the supply chain.

More info:

Fruit rotting in field

Fruit rotting in field

Sunburn

Cause: Insufficient bunch shading during prolonged high temperatures. 
Solution: There is no cure for affected fruit. Maintain good canopy cover and ensure bunch covers are applied properly. It may be necessary to pull a leaf down over the bunch for protection. 

 

Affected areas are dark and in later stages are covered by ashy grey spores.
Close up of later stage covered by ashy grey spores.

Cigar end

Cause: The fungus Musicillium theobromae (formerly known as Verticillium theobromae). It enters the fruit from the dead floral parts and extends 10 to 20 mm into the fruit. 
Solution: Cigar end is a minor disease and specific control measures are not warranted. 
Bunch ripens prematurely in the field, making the bunch unmarketable.

Mixed ripe

Cause: Various stresses (severe leaf spot, pest damage, water and nutrition) reduce the rate of fruit filling. 
Solution: Improve crop management to limit stresses on the plant.

Punctures or splits on fruit

Punctures or splits on fruit

Birds or bats

Cause: Birds and bats landing on the bunch to feed on nectar from immature flowers.

Solution: Cover bunches promptly and use thick covers. For Lady Finger apply covers before any bracts lift on the bunch. 

Bell injection

Cause: Incorrect bell injection technique.
Solution: Train staff to inject slightly above one-third from the top of the bell. 
Symptoms show as slightly raised yellow spots on small fruit or longitudinal cracks on growing fruit. The exposed tissue collapses and turns black.

Diamond spot

Cause: The fungus Cercospora hayi. Spores are produced on dead banana material. 
Solution: Diamond spot is a minor disease especially where control of leaf spot is effective. 

Rust or bronzing on fruit

Rust or bronzing on fruit

Left: early damage appears as a water-soaked area on the skin between touching fingers. Right: later development showing typical reddish-brown rust.

Banana rust thrips

Cause: Feeding by Chaetanaphothrips signipennis from bract fall to harvest causes a rust brown skin discoloration. This symptom should not be mistaken for maturity bronzing, which is more prevalent on the outer exposed areas of the fingers.
Solution: Soil treatments for banana weevil borer will help control the soil thrips population. Treat bunches at the time of bunch covering.
More info:
Banana rust thrips — general information and monitoring and control options
More images
The bronze-red blemish on the curved fruit surface first appears at the 'three-quarter full' stage and becomes more intense and extensive as the bunch fills.

Maturity bronzing

Cause: Oxidation of cell contents, possibly from a water and nutritional imbalance, causes the epidermal cells to discolour, lift and break. 

Control: In the short term, bunches should be harvested early before symptoms become more severe. Avoid water and nutrient stresses in the plant.
Symptoms are similar to maturity bronzing but are associated with chemical burn from injection for scab moth. Symptoms are commonly seen on lower hands and may cross to fruit ridges.

Spray burn

Cause: Incorrect chemical application rates, problems with compatibility or environmental conditions.

Solution: Check that you are using registered chemicals and are applying them at the correct rates. Make sure that your spray application equipment is cleaned regularly. 
Note irregular silvery patches speckled with black spots. In severe cases the skin splits, causing longitudinal cracks.

Silvering thrips

Cause: Feeding by Hercinothrips bicinctus.

Solution: This is a minor and rare pest of bananas grown in north Queensland. No specific treatments are required.
Upper: banana (strawberry) spider mite causes red to purple-black surface discolouration to cushion end. Lower: two-spotted mite damage; webbing is usually present.

Mites

Cause: Banana (strawberry) spider mite, Tetranychus lambi, feeding on the fingers. More severe infestation will result in the damage spreading over the entire fingers. 

Two-spotted mites, Tetranychus urticae, feed primarily on the tips of fingers, causing silver-grey superficial damage. Webbing forms ‘bridges’ between heavily infested fingers. 

Solution: Severe mite outbreaks are usually the result of poor insecticide management, especially foliar application of disruptive pesticides that destroy beneficial species such as the Stethorus spp. beetle. Treatments with a suitable miticide may be required during periods of hot, dry weather when mite build-up can be rapid.