A guide to identifying banana fruit fungal issues.

Posted on by Better Bananas

A guide to identifying banana fruit fungal issues.

Bananas are susceptible to various fungal diseases that can affect their fruit quality. Correctly identifying these fungal issues in banana fruit is crucial to understanding how to manage and prevent further damage. This guide explores some of the most common fungal problems that affect banana fruit.

If your issue isn’t listed here or you are having problems identifying what is causing damage to your crop check out the Better Banana’s problem solver section here. 

Sooty blotch
Sooty blotch
Sooty blotch water-soaked shadowing
Sooty blotch
Sooty blotch damage in ripe fruit
Sooty blotch damage in ripe fruit

Sooty blotch

  • Multiple fungal organisms are associated with the symptoms.
  • Presents as water-soaked shadowing.
  • Damages skin surface and can’t be removed by rubbing.
Sooty mould
Sooty mould powdery growth
Sooty mould - when zoomed it is possible to see insect casts (aphids)

Sooty mould

  • Caused by the combination of sap-feeding insects (banana aphids and mealybugs) and fungi, namely the genus Cladosporium.
  • The fungus grows on the honeydew secreted by aphids or mealybugs and the fungal infection is secondary.
  • Black powdery growth occurs in dark layered sheets which can be peeled away or removed by rubbing (but the stain remains).
Fruit speckle
Fruit speckle - smooth reddish brown to black spots (0.5-1 mm) with water-soaked margins.
Fruit speckle
Fruit speckle - heavy cases can see speckle coalesce
Fruit speckle affecting all fingers in cluster
Severe fruit speckle damage

Fruit speckle

  • Caused by multiple species of fungi including Colletotrichum musae, Fusarium oxysporum and Fusarium semitectum.
  • Occurs first on fruit neck.
  • Smooth reddish brown to black spots (0.5-1mm) with water-soaked margins.
  • Previously known as ‘swamp spot’, ‘salt and pepper spot’ and ‘Deightoniella spot’.
Deightoniella torulosa
Deightoniella torulosa.
Deightoniella torulosa
Spots are typically larger than fruit speckle (2-4mm) and sunken on green fruit.

Deightoniella spot

  • Caused by Deightoniella torulosa
  • Spots are typically larger than fruit speckle (2-4mm) and sunken on green fruit.
  • Less commonly detected in FNQ.

Download this information as a factsheet.

This information has been developed as part of the National Banana Development and Extension Program (BA19004) which is funded by Hort Innovation, using the banana industry research and development levies and contributions from the Australian Government. Hort Innovation is the grower-owned, not-for-profit research and development corporation for Australian horticulture. The Queensland Government has also co-funded the project through the Department of Agriculture and Fisheries.

Banana flower thrips

Posted on by Better Bananas

Flower thrips

Banana flower thrips (Thrips hawaiiensis) are a tiny pest frequently present in banana bunches. For most growers in Far North Queensland flower thrips are not the main bunch pest which leads to economic losses. However, large enough infestations can cause damage to fruit that does not meet market specifications. Damage caused by flower thrips is more significant in warm dry conditions with lower relative humidity, such as South East Queensland and northern New South Wales.

female Flower thrips to scale
Adult female flower thrips measure 1mm in length

Correct and timely bell injection is critical for the control of flower thrips. It must be performed when the bell is upright to ensure the insecticide solution provides protection to the entire bunch. Flower thrips are from the same family as Banana rust thrips (Chaetanaphothrips signipennis). Unlike banana rust thrips, flower thrips spend their entire life cycle on the banana plant, therefore, soil treatment does not provide control of flower thrips. 
 

Flower thrips cause damage to the peel of banana fruit from feeding and ovipositing (egg laying). These ovipositions resemble minute raised pimples on the young immature skin. These are readily seen because of a dark raised centre and can be confirmed by lightly touching the raised area with your fingertip. These oviposition marks almost disappear as the fruit matures. However, extensive damage from feeding from adult flower thrips can cause superficial scarring known as ‘corky scab’. This damage is usually confined to the lower hands (as flower thrips damage increases on lower hands as populations increase as they move down the bunch if it hasn’t been treated). Usually it is first noticeable on the outer whirl,  where the neck meets the cushion, but can extend to the outer curve of the fruit.  

Close up of flower thrips damageovipositions (pimples) on young banana fruit.
Severe flower thrips damage causing corky scab damage.

More information

This information has been prepared as part of the National Banana Development and Extension Program (BA19004) which is funded by Hort Innovation, using the banana industry research and development levies and contributions from the Australian Government. Hort Innovation is the grower-owned, not-for-profit research and development corporation for Australian horticulture. The Queensland Government has also co-funded the project through the Department of Agriculture and Fisheries.

Banana flower thrips – general information and management

Posted on by Better Bananas

Banana flower thrips Thrips hawaiiensis

General information and management

Occurrence and seasonality

Banana flower thrips are common in banana flowers and among the fingers of newly emerged hands. This pest is found anywhere bananas are grown but its damage is more significant in the less humid, warm and dry climate of South East Queensland and northern New South Wales. Flower thrips are active throughout the year, with increased activity in January through to April. However, as long as flowers are present they can continuously breed.

Adult female flower thrips measure 1mm in length

Description and life cycle

Female flower thrips cause the most damage. They are 1mm long with a pale brown head and thorax and have a black abdomen. They are generally found sheltering under the bracts or inside the flowers. Male flower thrips are smaller (about 0.7mm long), uniformly cream coloured and tend to occur on the outer surface of the bracts.

Adults and nymphs are found on newly emerged bunches and invade the fruit early when the bunch is still covered by its bracts. Recent work has found that flower thrips are present very early in bunch development, inside the bell whilst it is still upright. Flower thrips breed all year round if flowers are present and migrate progressively down the bunch as bracts lift.  The lifecycle takes about three weeks in summer, with full development from the egg to the adult taking place on the bunch or in other parts of the plant.

Damage

Damage to fruit is the result of superficial scarring caused by feeding and ovipositing (egg laying). Oviposition damage resembles minute raised pimples on the young immature fruit skin. These have a dark raised centre and can be confirmed by lightly touching the raised area with the fingertips.

Extensive feeding damage causes a ‘corky scab’, a slightly raised grey corky skin covering. This damage is usually confined to the lower hands (flower thrips damage increases on lower hands as populations increase as they move down the bunch, if it is untreated). Usually, it is first noticeable on the outer whirl, where the neck meets the cushion, but can extend to the outer curve of the fruit. 

Close up of flower thrips damageovipositions (pimples) on young banana fruit.
Severe flower thrips damage causing corky scab damage.

Monitoring

If flower thrips damage is being picked up in the packing shed, the best solution would be to speak to your bell injectors, revise training and ensure that bell injections are being performed correctly (right time and right position).

Flower thrips damage is easy to find in the shed, but it is also possible to find it out in the field. Monitoring for early detection of flower thrips can be done by examining bells of bunched plants every time you’re in the paddock. When large numbers of flower thrips are present, they cause bract-feeding patterns which are ‘lace-like’ in appearance and are lighter than the mauve bracts. These are more pronounced at trimming (when flower thrips populations are highest) and although bunches may already have damage, it gives you an early indication of high pest pressure allowing you to revise training with bell injectors, approximately 12 weeks earlier if assessing damage at harvest in the shed.

zoomed in bract feeding by flower thrips
Flower thrips feeding damage to bract, evident at trimming. Zoomed in for a clearer depiction of ‘lace-like’ feeding pattern.

Control

Chemical

Chemical control is best achieved with correct bell injection. Flower thrips can make their way between the bracts into the bell and damage very young fruit before bell injection. Therefore, to limit the extent of this damage, the timeliness of bell injection is important.  Inject bells whilst still upright. Increase the frequency of bell injecting during warmer months to account for increased plant growth (if possible, as short as every 4-5 days and extending out to every 7 days in winter). Always check the APVMA website for current chemical registrations before use. Below are insecticides currently registered (March 2023) and permitted for bell injection to control flower thrips.

Biological

A range of predatory bugs, predatory mites, ladybird beetles and lacewings can assist in reducing the build-up of flower thrips. Choosing chemical products that are less likely to kill these beneficial insects may assist in suppressing background pest populations.

More information

The Better Bananas team Department of Agriculture and Fisheries South Johnstone 07 4220 4177 or email betterbananas@daf.qld.gov.au

Download this information as fact sheets

This information is adapted from; Pinese,B., Piper, R 1994, Bananas insect and mite management, Department of Primary Industries Queensland

This information has been prepared as part of the National Banana Development and Extension Program (BA19004) which is funded by Hort Innovation, using the banana industry research and development levies and contributions from the Australian Government. Hort Innovation is the grower-owned, not-for-profit research and development corporation for Australian horticulture. The Queensland Government has also co-funded the project through the Department of Agriculture and Fisheries.

Fruit rotting after harvest

Posted on by Better Bananas

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:

Crown end rot research 

Fruit rotting in field

Posted on by Better Bananas

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

Posted on by Better Bananas

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

Posted on by Better Bananas

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. 


Solution: In the short term, bunches should be harvested early before symptoms become more severe. Avoid water and nutrient stresses in the plant.


More info:

Maturity bronzing—stretching the limits on fruit quality

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.

 

More info:

 

Spots of fruit

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Spots on fruit

Note slightly sunken black circular spots up to 5 mm in diameter. Inset: banana spotting bug (about 2 cm long).

Banana spotting bug

Cause: Feeding (sucking) by banana spotting bug, Amblypelta lutescens lutescens, usually on the exposed outer curve of the fingers.


Solution: Damage is more severe on blocks adjacent to rainforest. No specific treatments required. If more than 5% of bunches are affected, spot spray.   

Fruit speckle

Cause: Caused by multiple species of fungi including Colletotrichum musae, Fusarium oxysporum and Fusarium semitectum. Spores are produced in large numbers on dead leaf material during wet conditions and are spread in air currents to the fruit.  


Solution: Fruit speckle is generally a minor disease that can become problematic in seasonally unfavourable weather conditions. Under normal conditions, a fungicide leaf spot spray program should assist and keep levels low.


More info:

Note stings (minute pinholes) on the surface. A small drop of sap usually forms at the sting site.

Fruit flies

Cause: Banana fruit fly, Bactrocera musae, and Queensland fruit fly, Bactrocera tryoni, laying eggs (stinging) in the pulp of banana just below the skin. The banana fruit fly can sting green fruit but the Queensland fruit fly only stings ripening or yellow fruit. 


Solution: Chemical control should not be required since fruit is harvested at the hard green stage before either of the fruit flies can complete their life cycles. Do not leave over ripe fruit in the field. If mixed ripe fruit causes hot spots in the plantation, spot spray with an appropriate chemical. 

Note raised 'pimples' on the skin.

Flower thrips

Cause: Scarring from egg-laying by flower thrips, Thrips hawaiiensis on young fruit when still covered by the bracts.


Solution: Insecticide injection at bell emergence for control of scab moth also controls flower thrips. 


More info:
Banana flower thrips – general information 

The spots or rings are usually on the lowest points of fingers where chemical runs if the bunch is oversprayed.

Spray burn

Cause: Spraying with excessive volumes of chemical or inappropriate chemical use. 


Solution: Use only registered chemicals and apply according to the label directions.

Sooty blotch

Cause: Multiple fungal organisms are associated with the symptoms. 


Solution: Lady Finger and Ducasse are more prone to sooty blotch than Cavendish-type bananas. A post-harvest dip of sodium hypochlorite at 100 ppm for 5 minutes followed by immediate rinsing, is highly effective in removing sooty blotch.


More info:

Sooty mould

Cause: Sooty mould fungi that develop on the honeydew secretions of the banana aphid, Pentalonia nigronervosa.


Solution: Natural control by parasites and predators provides adequate suppression. Infestations are more obvious during cooler weather in autumn and spring. Spot treatment with a suitable pesticide is occasionally required as the mould can be difficult to remove from fruit.


More info:

Scabs on fruit

Posted on by Better Bananas

Scabs on fruit

Surface feeding by the larvae causes scarring.

Scab moth

Cause: Larvae of Nacoleia octasema feeding on the fruit between the bunch stalk and the hand. Only occurs from bunch emergence to bract fall.


Solution: Newly emerged bells require pesticide injection while they are still upright. When the plants are growing quickly during summer, treat blocks at least weekly. 


More info:

Banana scab moth – summary

Surface feeding by the larvae causes scarring.

Sugarcane bud moth

Cause:  Small grey larvae of Opogona glycyphaga. They feed and pupate mainly towards the tips of the fingers and where the flower end of a lower finger meets a finger in the hand above.


Solution: This pest lays its eggs on fruit after all the bracts have fallen. Treat bunches with insecticide during bunch covering. 

Banana fruit caterpillar

Cause:  Larvae of Tiracola plagiata feeding on leaves and fruit. Damage is usually confined to a few bunches and feeding on fruit is confined to the outside of fingers.


Solution: Although attack to a single bunch can be very severe, only a few bunches are damaged and specific treatments are not usually needed. Standard treatments for rust thrips and sugarcane bud moth help to control fruit caterpillar.  If damage is noted on more than 5% of bunches, treat with a pesticide. 

Corky scab

Cause:  Scarring from feeding and egg-laying by flower thrips, Thrips hawaiiensis on young fruit when still covered by the bracts.


Solution: Insecticide injection at bell emergence for control of scab moth also controls flower thrips.


More info:

Banana flower thrips – Summary

Rub

Cause:  Rubbing between the bag and young fingers due to prolonged strong winds. Leaves rubbing against the fruit cause similar symptoms.


Solution: Retaining existing vegetation or planting specific windbreak trees can reduce the damage caused by strong winds.