News – Page 16 – Better Bananas

Discoloured leaf petioles

Banana streak virus

Cause: The banana streak virus (BSV).

Solution: Do not take planting material from infected plants. Eradicate infected plants where symptoms are observed.

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:

Nitrogen deficiency

Cause: Insufficient nitrogen available for the plant due to inadequate fertiliser applications or leaching and gaseous loss of the nitrogen fertiliser applied.

Solution: Appropriate application of nitrogen fertiliser. You need to know your soil type, climate, past fertiliser program, and soil and leaf analysis results when determining the fertiliser rate.

Yellow leaves

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:

Nitrogen deficiency

Cause: Insufficient nitrogen available for the plant due to inadequate fertiliser applications or leaching and gaseous loss of the nitrogen fertiliser applied.

Solution: Appropriate application of nitrogen fertiliser. You need to know your soil type, climate, past fertiliser program, and soil and leaf analysis results when determining the fertiliser rate.

Potassium deficiency

Cause: Reduced availability of potassium for plant uptake. Enhanced by leaching losses of potassium and/or inappropriate fertilisation.

Solution: Appropriate application of potassium fertiliser. Knowledge of your soil type, climate, past fertiliser program, and soil and leaf analyses need to be considered in determining fertiliser rate.

Magnesium deficiency

Cause: Reduced availability of magnesium for plant update. Usually due to inappropriate fertilisation causing an imbalance.

Solution: Appropriate application of magnesium fertiliser. Knowledge of your soil type, climate, past fertiliser program, and soil and leaf analyses all need to be considered in determining fertiliser rate.

Water-logging

Cause: Poor soil aeration which reduces root function and leads to water and nutrient stress.

Solution: Depends on soil type and situation but usually involves surface and subsurface drainage works.

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.) which 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: There is no cure for infected plants. Avoid stress conditions. Ensure adequate moisture levels are maintained during the dry season.

Spots on leaves

Leaf spot (yellow Sigatoka)

Cause: The fungus Pseudocercospora musae (formerly known as Mycosphaerella musicola). Early stages of development appears as light yellow streaks 1 to 2 mm long. Streaks enlarge in time to become spots.

Solution: Ensure the leaf spot management program is carried out effectively. The program should include cultural (deleafing, drainage) and chemical (fungicides, oils, application timing, coverage) practices.

More info:

Black Sigatoka

Biosecurity Alert

Cause: The fungus Pseudocercospora fijiensis (formerly known as Mycosphaerella fijiensis). In the early stages of development, black Sigatoka appears as rusty red streaks up to 5 to 15mm. These symptoms are more obvious on the underside of leaves. Streaks enlarge over time to become spots.

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

Biosecurity: Importation of all banana material (fruit, leaves, planting material) is prohibited without approval. A biological barrier is now established, reducing the number of susceptible bananas between the Torres Strait/Papua New Guinea, where the disease exists and the Far North Queensland banana production areas.

More info:

Leaf speckle

Cause: Several fungi including Mycosphaerella musae (banana leaf speckle or common speckle), and Ramichloridium spp. (tropical leaf speckle) can produce a range of symptoms. These fungi are spread by wind in moist weather and are more tolerant of cool conditions than the leaf spot fungus.

Solution: The leaf spot management program normally provides control of speckle. If better control is needed, apply fungicides by ground rig which targets the underside of leaves.

Cordana leaf spot

Cause: The fungus Neocordana musae. Large numbers of spores produced on the underside of lesions are spread during wet windy weather. The fungus mainly enters the leaf through injuries. It is common on plants weakened as a result of water-logging or drought.

Solution: The leaf spot program provides adequate management of cordana leaf spot.

Southern cordana leaf spot

Cause: The fungus Cordana johnstonii. This disease is present in the tropics and distribution is limited. It is frequently seen on unsprayed Ducasse plants, and in areas of high elevation under cooler weather conditions. Lesion size is significantly smaller than Cordana musae, approximately 10 by 15 mm. As with Cordana musae, spores form abundantly on the underside of leaves on mature lesions.

Solution: The leaf spot control program should manage this disease.

Banana rust

Cause: The fungus Uredo musae. A disease with limited distribution, it is seen within plantations near tree lines and buildings which reduce spray coverage. Banana rust occurs predominantly on older leaves. Therefore fungicide applications should be applied via ground rig.

Solution: The leaf spot program should provide adequate management of rust.

Herbicide drift

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.

Mite damage

Cause: Feeding by the banana spider mite, Tetranychus lambi, or the two-spotted mite, Tetranychus urticae, causes tissue to die, resulting in bronzed areas under 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:

Transparent scale

Cause: The scale insect Aspidiotus destructor sucking nutrients from the leaf cells.

Solution: Natural predation by beetles, parasitism by wasps and oil sprays used for leaf spot help to suppress scale. For small outbreaks, cut off affected leaves. Avoid the use of foliar sprays that will interfere with natural control agents. Specific insecticide treatments are not recommended or required.

Spiralling whitefly

Biosecurity Alert

Cause: The insect spiralling whitefly (Aleurodicus dispersus). The white adults and nymphs occur on the underside of the leaf. The name comes from the white trail in which the eggs are laid. Its sap-sucking reduces vigour, and the production of honeydew supports the growth of sooty mould which can cover fruit and leaves.

Biosecurity: Report all suspicious symptoms immediately to Biosecurity Queensland (13 25 23)

More info:

Queensland Department of Agriculture and Fisheries

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.

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

Posted on 2018-01-17 by Better Bananas

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.

More info:

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

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

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.

Banana bunchy top

Biosecurity Alert!

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.

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:

•  Better Bananas
•  Australian Banana Growers Council
•  Queensland Department of Agriculture and Fisheries
•  Plant Health Australia
•  New South Wales Department of Primary Industries

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

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.

More info:

A guide to identifying fungal fruit diseases

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

Posted on 2018-01-15 by Better Bananas

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.

More information...

For more information on how to protect your farm from Panama disease TR4, visit the Panama TR4 protect website panamatr4protect.com.au. The website provides information and practical advice for all banana growers and community members on how to protect our banana farms and our communities.

Biosecurity assistance is available

The National Banana Development and Extension Team are available to assist Australian banana growers who would like to start or make improvements to their biosecurity plan.
Contact our team today via email betterbananas@daf.qld.gov.au or phone 07 4220 4152.

Banana variety research

Posted on 2018-01-15 by Better Bananas

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.

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.