Plants

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Plants symptoms and causes

Plants kink, bend or fall over

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Plants turn yellow and die

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Small and stunted plants

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Stem shatters

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Internal stem discolouration

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Green leaves dropping

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Leaves bunching at top of plant

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Roots discoloured internally

Posted on by Better Bananas

Roots discoloured internally

Burrowing nematode, other nematodes

Cause: Burrowing nematode Radopholus similis feeding on the cells in the root cortex. Many species of nematodes in the soil also parasitise the roots of bananas.

Solution: Nematodes other than burrowing nematode are not usually a problem in the tropics. Check a random sample of roots over the whole field to determine the extent of the problem and if a nematicide treatment is necessary.

Leaves bunching at top of plant

Posted on by Better Bananas

Leaves bunching at top of plant

Choking of leaves

Cause: Choking can be due to a genetic abnormality related to a particular variety or off-type, or from stresses (water-logging, cold, water or nutrient shortage, 2,4-D, banana streak virus and bunchy top). These causes limit the normal elongation of the true stem so that the leaves appear ‘bunched up’. 

Solution: Choose varieties less prone to choking and cull tissue-cultured off-types showing these symptoms. Check for diagnostic virus indicators. Improve management to limit stresses on plant.

Green leaves dropping

Posted on by Better Bananas

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

Posted on by Better Bananas

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

Posted on by Better Bananas

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

Posted on by Better Bananas

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.

Advanced symptoms of BBTV

Banana bunchy top

Biosecurity Alert!

Cause: The banana bunchy 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.

Reporting: Under state legislation, banana bunchy top disease must be reported. If you have seen plants with banana bunchy top symptoms within the Southern Queensland banana biosecurity zone, or the NSW Banana Bunchy Top Virus Control Zone contact the Banana Bunchy Top Hotline on 1800 068 371.

If you have seen banana bunchy top outside of these areas, you must report it within 24 hours to the Biosecurity authority in your state (Biosecurity Queensland on 13 25 23, or NSW DPI Biosecurity Hotline 1800 680 244) or the Exotic Plant Pest Hotline on 1800 084 881.

More Information:

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

Posted on by Better Bananas

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

Posted on by Better Bananas

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.

More info:

Banana weevil borer – general information

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.