Curled or distorted leaves

Curled or distorted leaves

Spike leaf

Cause: A temporary shortage of calcium caused by rapid growth. Most common in spring and early summer.
Solution: Avoid sudden bursts of growth by using regular, light fertiliser applications. A foliar application of calcium nitrate at 10 g/L in early spring will reduce the problem.  
Left: damage to leaf. Note twists in leaf tip. Right: close-up of damage. Note the cracked and raised veins.

2,4-D damage

Cause: Spray drift of 2,4-D onto green parts of the plant.
Solution: Take efforts to avoid spray drift onto leaves. Plants should grow out of it. 

Tissue-cultured off-type

Cause: A genetic abnormality that occurs in tissue-cultured plants.
Solution: Destroy affected plants and set additional following suckers on nearby plants.

Banana streak virus

Cause: The banana streak virus (BSV). The streaks or flecks on leaves become progressively darker with age and the leaves may die. 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.

Leaves with dead edges or patches

Leaves with dead edges or patches

Manganese toxicity (dead patches)

Cause: Excess manganese in the plant due to the presence of manganese nodules in the soil profile and water-logging.
Solution: Confirm the diagnosis with a leaf analysis. Improve soil drainage and soil structure. Avoid planting bananas in poorly drained soils.

Salt toxicity (dead edges)

Cause: A build-up of salt in the plant from high soil or water salinity.
Solution: Confirm the diagnosis with tissue or water analysis. Water heavily to leach salt out of the root zone. Seek alternative sources of water. Avoid excessive applications of fertilisers containing chloride.

Mites (dead edges)

Cause: Feeding of the banana spider mite Tetranychus lambi, or the two-spotted mite, Tetranychus urticae on the underside of leaves. Severe outbreaks are usually the result of poor insecticide management which has destroyed beneficial insects.
Solution: Treat with an appropriate miticide. Ensure adequate coverage to the underside of the leaves.

Water stress (dead patches)

Cause: Severe water stress during hot, dry periods.
Solution: Apply more water during periods of high demand. Water scheduling devices help to plan irrigation. 

Herbicide damage

Cause: Spray drift of contact herbicides such as paraquat onto the plant. 
Solution: Avoid spray drift onto leaves. Affected plants should grow out of the symptoms. 

Streaks on leaves

Streaks on leaves

Variegation

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

Solution: Destroy affected plants and set additional following suckers on neighbouring plants. 

Banana streak virus

Cause: The banana streak virus (BSV). The pale streaks or flecks on the leaves become darker with age. Symptoms of cucumber mosaic virus are similar.

Solution: Eradicate infected plants and set additional following suckers on neighbouring plants. Do not take planting material from infected plants.

Zinc deficiency in young tissue culture plants.

Zinc deficiency

Cause: Insufficient zinc available to the plant. 

Solution: First confirm the diagnosis with a leaf analysis test. Apply zinc fertiliser at the rate recommended on your analysis result. 

Note dark green flecks develop along the veins of the leaves, producing a ‘dot-dash’ pattern which ‘hooks’ into the midrib from the leaf blade.

Bunchy top

Cause: The banana bunchy top virus (BBTV) which is spread in 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:

Cucumber mosaic virus

Cause: Cucumber mosaic virus (CMV). This virus has a wide host range and can be spread to bananas by aphids. 

Solution: Disease incidence is sporadic and generally low. Control measures are not warranted. Do not take planting material from infected plants.

October to November streak

Cause: A physiological disorder of unknown cause which generally occurs during October and November. 

Solution: There is no known cure. Plants will grow out of it. 

Chlorotic patching

Cause: A physiological disorder that indicates the plant is suffering stress. It usually occurs in spring and can be related to water-logging.

Solution: Determine the exact cause of plant stress. Check for corm or root damage from banana weevil borer or nematodes.

 

Colours on leaves

Colours on leaves

Sooty mould (blackened leaves)

Cause: A fungus growing on the honeydew secretions produced by insects such as      aphids, scales and bugs.

Solution: Natural control by parasites and predators usually provides adequate            control of these pests. Chemical sprays specifically to reduce insects which promote honeydew and sooty mould are seldom required.

Juvenile plants (red-purple blotches on leaves)

Cause: The juvenile stage of young Cavendish bananas and some other varieties usually has red-purple blotches on the leaves. This is normal.

Solution: No control is needed and plants grow out of this symptom.

 

Mite damage (bronzed leaves)

Cause: Feeding on the banana spider mite, Tetranychus lambi, or the two-spotted mite, Tetranychus urticae, on the underside of leaves.

Solution: Treatment is usually not necessary because predatory beetles Stethorus spp. maintain adequate natural control. If these beetles are not present, and monitoring results show the level of damage is severe, treat with an appropriate miticide. Ensure adequate coverage to the underside of leaves.

More info:

Panama disease

Panama disease research and development

Panama disease is a soil borne disease caused by the fungus Fusarium oxysporum f.sp. cubense.  Different strains of the disease are known as races. The most notable races that affect bananas include:
  • Race 1 – infects Lady Finger and Ducasse bananas but not Cavendish.
  • Subtropical race 4 – infects Lady Finger,  Ducasse and Bluggoe, as well as Cavendish bananas in subtropical regions of Australia.
  • Tropical race 4 –  is the most virulent race, affecting most varieties of bananas including Cavendish.
In March 2015, Panama disease tropical race 4 was detected in the main growing region in Far North Queensland. Over 95% of Australia’s bananas are Williams Cavendish. This variety is susceptible to the disease and therefore slowing the spread is vital to allow time to find solutions to protect our $600 million banana industry.
Our Australian researchers are focused on various aspects of the disease, and we will continually update this website with the latest Panama R&D outcomes as they become available. 

Symtom Photo
Williams Cavendish plant showing symptoms of Panama disease tropical race 4

More information...

For more information on how to become Panama TR4 ready, visit the Panama TR4 Ready campaign website panamatr4ready.com.au. The website provides information and practical advice for all members of the community on how to protect our banana farms and our communities.

Banana variety research

Banana variety research — the search for new resistant varieties

The search for new banana varieties that have both desirable agronomic characteristics and resistance to pests and diseases, especially Panama disease tropical race 4, is a current hot topic in the banana industry. This page gives you background into banana breeding techniques and links you to the latest progress updates from industry funded variety trials. 

How do you 'breed' a new banana variety?

The development of new banana varieties is a slow and costly process, with high levels of infertility making it difficult to do conventional breeding from some commercially important varieties like Cavendish.

Banana breeding techniques fall into three broad categories:

  • Conventional breeding is when fertile male and female lines are crossed using pollen to produce seeds. The seeds are germinated and the seedlings are screened for the desired improved attributes. This method is extremely time consuming and labour intensive, however, there are many benefits by using and introducing the wider range of genetic diversity from wild banana cultivars. Improved banana cultivars are imported into Australia for evaluation.
  • Mutation breeding and somaclonal variation uses induced mutations in existing cultivars to produce plants with desirable attributes such as pest or disease resistance, improved plant stature and increased yield. 
    Selection of improved cultivars via somaclonal variation (off-types), induced by plant tissue culture, was pioneered by the Taiwan Banana Research Institute (TBRI) to develop Cavendish varieties with increased levels of resistance to Panama disease tropical race 4.

    Mutagenesis applies chemical or gamma irradiation treatment to tissue cultured plants to fast track genetic changes, thereby causing a higher rate of off-type plants than somaclonal variation induced by tissue culture alone. Australian scientists were at the forefront of developing and using this method in banana in the 1990s. Both methods produce plants with potentially desirable characteristics, however, there are also many plants that have detrimental changes. 

  • Genetic modification involves the manipulation of the banana DNA, by inserting identified genes for desirable characteristics from bananas or other organisms. Newer techniques include the manipulation of the plant’s own genes without the introduction of any external genetic material.

What types of 'breeding' is the banana industry investing in?

There are two key variety initiatives funded by the Australian banana industry. Currently through the project Improved Plant Protection for the Banana Industry (BA16001), which is part of the Hort Innovation Banana Fund, the industry is continuing to invest in variety importation and screening. This means that we import varieties – either from conventional breeding programs or somaclonal selection programs, ensure they are disease free and trial them under research agreements with each respective breeding program. 

There are three field screening sites for these varieties. 

The second key activity under way is the use of somaclonal selection to develop resistant varieties. As mentioned earlier, somaclonal selection relies on induced mutations in existing varieties, to produce plants with desirable attributes such as, pest or disease resistance, improved plant stature and increased yield. To increase the amount of variation of somaclonal selections, researchers are using mutagenesis to induce genetic mutations in selected cultivars by means of gamma irradiation. As part of this work, four varieties that have improved levels of resistance to Panama disease tropical race 4 have recently undergone mutagenesis to improve their agronomic characteristics.

Did you know...

Department of Agriculture and Fisheries scientists, used mutagenesis in the early 1990s to develop DPM25 as a Cavendish selection. DPM25 has acceptable resistance to Panama disease subtropical race 4 and similar yield as Williams. It was developed from the Extra Dwarf Cavendish, Dwarf Parfitt, using tissue culture and gamma irradiation. 

Image on left is photo of Dwarf Parfitt, an Extra Dwarf Cavendish cultivar with resistance to Panama disease subtropical race 4. Image on right is photo of DPM25. This selection was developed through mutagenesis of the Dwarf Parfitt cultivar. DPM25 shows improved agronomic characteristics and acceptable resistance to Panama disease subtropical race 4.

Steering the direction for variety R&D

With the limited resources available and the high priority for identifying resistant varieties, it is essential that the research and development investment decisions, represent the best value for the Australian banana industry. A key part of this is the development of the Banana Variety Subcommittee (BVS). The BVS consists of banana growers, supply chain businesses and researchers, and focuses on the broad strategic issues associated with variety importation and development. If you have any questions please don’t hesitate to talk to one of the BVS members or contact the better bananas team via email betterbananas@daf.qld.gov.au or phone 13 25 23.

The mutagenesis trial work is part of the Fusarium Wilt Tropical Race 4 Research Program (BA14014), which is funded by Hort Innovation, with co-investment from the Queensland Department of Agriculture and Fisheries and contributions from the Australian Government. 

The variety importation and screening activity is part of the Improved Plant Protection for the Banana Industry Program (BA16001)
. This project has been funded by Hort Innovation, using the banana research and development levy, co-investment from the Queensland Department of Agriculture and Fisheries and contributions from the Australian Government.

Hort Innovation is the grower-owned, not-for-profit research and development corporation for Australian horticulture.