Agronomic evaluation Lady Finger-like varieties

Posted on by Sarah Williams

Agronomic evaluation of Lady Finger-like varieties (December 2022)

Lady Finger-like varieties from Brazil under trial at South Johnstone

By Jeff Daniells, Katie Robertson, Sharan Muthukumar and Carole Wright (August 2024)

Latest update...

Several Fusarium wilt Race 1 resistant Lady Finger-like varieties are being assessed for agronomic performance at the South Johnstone Research Facility. The plant crop data and a summary of the results is available below. 

The first ratoon harvest is already underway with harvest commencing in May 2024. The trial will be completed after the first ratoon harvest. Local taste panel results for varieties will be available then. Results from Panama disease Race 1 screening available next year will help guide any future on-farm studies.

Those who attended the September 2023 field walk had an opportunity to see plant crop bunches of these Lady Finger-like varieties. A video field walk through the block, prepared for the 2023 Industry Roadshows in NSW at about that time, is available.

Background

According to the ‘Australian Horticulture Statistics Handbook 2022/23’ the annual production of Lady Finger banana in that year was 11,228 t compared to 363,023 t of Cavendish, so Lady Fingers represent only about 3% of overall banana production. However, the farmgate value of Lady Finger production can be estimated as worth about $30 million, which because of the higher price paid for Lady Finger per kg of fruit, represents about 5% of the overall banana industry. But whatever way you want to look at it, the Lady Finger industry is an important industry in its own right.  In New South Wales the Lady Finger industry is proportionally much more important than it is overall for Australia.

In the April 2024 edition of Australian Bananas (see here pp 26-27) we drew attention to the constraint that Fusarium wilt Race 1 has placed on Lady Finger production in Australia. Varieties with resistance have been sought and evaluated over time, but while many have been identified with resistance, none have so far measured up as replacements for the Race 1 susceptible Lady Finger in the marketplace. So where possible, affected growers have sought new ground not infested with the pathogen.

In 2019/20 some new Lady Finger selections, Lady Finger hybrids and Sugar hybrids were imported from banana breeding programs in Brazil to evaluate in Australia. As described in the April article in Australian Bananas, some of these are being screened against Race 1 on the Atherton Tablelands. Here in this article, we present results from the plant crop of their agronomic evaluation at South Johnstone. This evaluation is part of the project BA21002 – ‘New varieties for Australian banana growers’.

Trial results in plant crop

Tissue cultured plants of 3 Lady Finger selections, 4 Lady Finger hybrids and 2 Sugar (Silk) hybrids were field planted in December 2022 at South Johnstone DAF. Pacovan, SCS451 and the hybrids all came from Brazil. The 6 hybrids from the program of EMBRAPA are all reported to be resistant to both Panama disease Race 1 and yellow Sigatoka. Japira and Pacoua are also reported to be resistant to black Sigatoka. SCS451 is from the program of EPAGRI and was purported to have tolerance to Panama disease Race 1. Bunch emergence commenced in May 2023, and harvest was completed in December 2023.

Pacovan Ken
Pacovan Ken were more pendulous than Lady Finger
Plantina lady finger hyrbid
Platina is shorter in stature than the other Lady Finger hybrids
Pacovan
Bunches of Pacovan were more pendulous than Lady Finger

Unfortunately, all except one of the Lady Finger (Improved) control plants were tissue culture offtypes. Thus, there are serious limitations when wishing to compare the new selections with the industry standard, Lady Finger. Nevertheless, reliable comparisons can be made amongst the new varieties. The agronomic and yield results from the plant crop are presented in the table below. Relative comparisons from previous studies suggest that for the Lady Finger data included in the table, the pseudostem height is indicative, but the duration from planting to harvest would usually be a little slower resulting in bunch weight/12 months being more in line with that obtained for SCS451.

Table: Selected yield and plant characteristics of varieties in the plant crop

Summary of results

A summary of the results and observations made are as follows:

  • The highest yielding varieties (per unit of time) were Pacovan, Pacovan Ken and SCS451, which were all significantly higher yielding than Tropical, Princesa and Japira. 

  • The tallest variety was Japira and the shortest in stature was SCS451. Several aspects of crop management are more difficult with the taller varieties.

  •  Japira, Pacovan Ken and Pacovan had significantly longer fruit on the 3rd hand, while fruit of Tropical and Princesa was significantly shorter.

Where to from here?

The first ratoon harvest is already underway with harvest commencing in May 2024. The trial will be completed after the first ratoon harvest. Local taste panel results for varieties will be available then. Results from Panama disease Race 1 screening available next year will help guide any future on-farm studies.

More information will be made available as the trial progresses.

This research has been funded as part of the project New varieties for Australian banana growers (BA21002), 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.

Chemical treatment of mites

Posted on by Better Bananas

Chemical treatment of spider mites

Restricting the use of chemicals that cause mite population flares

Some chemicals are associated with mite flares. This can be due to several reasons but primarily it is because these chemicals either encourage the mites to lay more eggs (the neonicotinoids, e.g. imidacloprid) or eliminate natural predators (the synthetic pyrethroids, e.g. bifenthrin). Where possible, avoid using these chemicals or if they must be used, time their use to the low-risk periods for mite flares, such as winter.

Correct application of miticides

Firstly, it’s important to check to ensure that live mites are still present and it’s not residual damage that’s still visible. With only a limited number of miticides available to the banana industry, it is important for treatment efficacy and long-term availability of these products that they are applied correctly.

  • Avoid using neonicotinoids for control of Banana weevil borer and Banana rust thrips (e.g. imidacloprid), particularly if hot dry conditions are expected. These chemicals can cause mite flares as they encourage mites to lay more eggs.
  • Avoid using broad spectrum pyrethroids (e.g. bifenthrin) as these products will remove the predator (beneficial) population. There is also the risk of spider mite populations developing resistance to these chemicals.
  • Miticides will not provide instant results and monitoring after spray applications is required as it may take 2-3 days before the mites begin to die.
  • Apply miticides in the cooler parts of the day as the leaves will close up during the middle of the day making full leaf coverage difficult to achieve. Mites are generally found on the undersides of the leaves therefore it is important that the leaves are open at the time of application.
  • Apply miticides with at least 400 L/ha and up to 600 L/ha of water to ensure good coverage. Poor coverage will result in limited mite mortality and may create chemical resistance problems.
  • Rotate between the available modes of action, chemical groups and abide by the restricted number of annual uses for each product to minimise the chance of chemical resistance issues.
  • Knockdown miticides (e.g. fenbutatin oxide) will only control nymphs and adults and therefore may require a follow up application 10–14 days later to control mites that have hatched from the eggs.
  • Some miticides are referred to as ovicides (e.g. clofentezine) meaning they only control the eggs, preventing them from hatching. These must be applied with a knockdown miticide to control the adult population. Follow label instructions for resistance management as ovicidal miticides have a history of resistance development if over used.

Actives registered for control of spider mites in bananas

Always check the current registration status of chemicals before use by visiting the Australian Pesticides and Veterinary Medicines Authority website (Click here) and always follow label directions.

Download this information as a factsheet

For more information contact

The Better Bananas team
Department of Agriculture and Fisheries
South Johnstone
Email betterbananas@daf.qld.gov.au 

 
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.

Natural predators of spider mites

Posted on by Better Bananas

Natural predators of spider mites

Natural predators are beneficial insects, that actively hunt and consume specific pest species. Spider mites have many natural predators including lady beetles, predatory mites, rove beetles, and predatory thrips. These natural predators need to be protected through conscientious spray programs (avoiding disruptive sprays) and some can be purchased from suppliers for augmentative releases to address spider mite population flares. Here we investigate two of the key natural predators and how they work to control spider mites.

Stethorus

The small, shiny, black mite-eating ladybird beetle or Stethorus is one of the most important predators of spider mites in bananas. Three species of Stethorus occur in bananas, but the main species is Stethorus fenestralis. All three species appear identical to the naked eye and all species are specialist spider mite predators.

Stethorus numbers increase following mite flares, as mites provide ample food supplies that allow Stethorus’ populations to flourish and eventually bring the mite levels back under control. Stethorus are high-density predators, meaning they are attracted to mite hotspots.  Interestingly, both adult and larval Stethorus beetles primarily feed on mites, making them very effective predators against these pests.

Stethorus adult 2
Adult Stethorus beetle

The life cycle of Stethorus

There are four distinct stages in the life cycle of Stethorus and it is important to recognise each of these stages. The elongated, translucent to pale brown eggs are laid singly under the leaves, either on or close to the mite colonies. The eggs are about 0.2 mm long and can easily be distinguished from the smaller spherical (and usually more numerous) mite eggs. Mite eggs are not visible to the naked eye, and a hand lens would be necessary to view them in the field.

Larvae are hairy and vary in colour depending on their age. Larvae go through four stages of maturation, each separated by a moult. Young larvae are pale cream becoming dark grey at maturity. Fourth-stage larvae eventually stop feeding when they are about 2 mm long and attach themselves to the leaf where they pupate.

The pupae are black, hairy and about 1 mm long. Pupae may be found anywhere on the underside of the leaf; however, they tend mostly to be found close to or on the midrib. The pupal stage is easily seen on a leaf, as a skin remains after the adult emerges. To determine whether a pupa is alive or is simply an empty pupal skin, smear it gently with a finger. A wet streak will indicate it was alive and if no wet streak is produced it, was an empty skin.

Adults are shiny black, almost circular beetle and are about 1 mm long. They also occur on the underside of the leaf. Where there is a high incidence of mite infestation, there may be more than fifty adults under one leaf, although there are usually less than ten when mite populations are in check.

Looking after your Stethorus population

Broad spectrum insecticides are a major cause of mite flares because they destroy beneficial predators like Stethorus. Avoid using these chemicals (e.g. products containing bifenthrin) to control mites. Check your leaves to see if you have Stethorus present and get a gauge on the population levels. Although research specifically in bananas hasn’t yet been undertaken to determine how many Stethorus need to be present to control spider mites, they can keep spider mite populations in check when spider mite pressure is low.

Stethorus egg
Stethorus egg
Stethorus larva
Stethorus larva
Stethorus pupa
Stethorus adult
Stethorus adult

Californicus

Some predatory mites are commercially available for purchase to apply in the field. The more common predatory mite species Neoseiulus californicus (‘Californicus’) is described as an ‘aggressive and robust mite’.

Californicus mites are less than 1mm long and are pear-shaped. Their colouring is dependent on diet but can be clear to pink or orange. Eggs are clear to white, oval-shaped and similar to that of the eggs of the two-spotted spider mite, but distinctively larger. Females can lay up to 4 eggs per day, eggs tend to be laid on the underside of the leaves along veins or on leaf hairs.

 Adult Californicus can consume up to 5 adult spider mites daily and can live for up to 20 days. These beneficial insects can even flourish even when prey is scarce, as they are also able to consume alternate food sources such as pollen or other small insects. However, research has shown that reproduction and developmental rates are increased when Californicus exclusively feed on spider mites.

Californicus is known for its resilience to differing environmental conditions. They remain active in both warm and cool temperatures and can survive well in both high and low humidity better than most other predatory mites. However, their optimal conditions are between 16-32˚ C with a relative humidity range of 40-80%. In optimal conditions (30˚ C), their lifecycles can be as fast as 4 days, almost twice as fast as that of their prey. Californicus are also less sensitive to pesticide residues which enables faster re-establishment after chemical applications.

The use of predatory mites as a biological control for spider mites has been trialled on commercial banana farms in Far North Queensland. Some growers release the predatory mites monthly as a preventative treatment for mite flares. For more details on how to release, and release rates see Bugs for Bugs’ instructions here or Natural Solutions’ instructions here.

Download this information as a factsheet

For more information contact:

The Better Bananas team
Department of Agriculture and Fisheries
South Johnstone
Email betterbananas@daf.qld.gov.au 

 
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.

Mite predators and monitoring

Posted on by Better Bananas

Encouraging spider mite predators

Promoting predatory insects to manage mite levels is best done by limiting the use of harmful chemicals, such as broad-spectrum insecticides and miticides, which affect beneficial predatory mites and Stethorus. 

Stethorus, the shiny black pinhead-sized lady beetles, are naturally occurring mite predators. They tend to increase in number when spider mite populations are high, as they utilise spider mites as a food source to survive. However, there may be a delay in their population growth due to the initial lack of spider mites.

Stethorus adult 2
Adult Stethorus beetle

Predatory mites such as Neoseiulus californicus (Californicus) and Phytoseilus persimilis (Persimilis) can also be purchased for release in your blocks from biological agent suppliers. It has been found that Persimilis may be the more efficient predator in south-eastern Queensland and northern NSW, as it utilises the webbing of the two-spotted spider mite, to locate its prey. While, in Far North Queensland, it’s advised to use the predatory mite Califonicus due to its suitability to the climatic conditions and its effectiveness against the predominant predatory mite, the banana spider mite.

Click here to read more about predators and other beneficial insects

Monitoring mite populations

Mites have a short life cycle which can be as short as 7-10 days during hot-dry conditions and as long as 4 weeks. Over summer months, weekly monitoring is preferable, however, fortnightly is sufficient during cooler, wet conditions. To monitor for the presence of mites, check plants for overall mite damage. The following categories can be used as a guide for the assessment of damage on the underside of leaves.

1 = Low

 

A few mite colonies on leaves and minor (more than one or two) localised bronzing on the under surface of leaves

Monitoring mite populations low mite levels

2 = Moderate


Mite colonies are scattered but numerous; bronzing is clearly evident on leaves (patchy but starting to coalesce) but the damage is contained within the interveinal areas.

Monitoring mite populations moderate mite levels

3 = High


Mite colonies coalescing and bronzing damage over most of the leaves.

 

Monitoring mite populations high mite levels

Applying miticides may be unnecessary if you have low to moderate levels (categories 1 or 2) of spider mite damage and healthy predator populations. To understand mite populations, a X10 magnifying glass is needed to observe all stages of mites (including eggs, nymphs and adults). A healthy predator population may look like finding predatory eggs and nymphs near the mite colonies. This may include finding small black Stethorus beetles. Stethorus are found mainly on the underside of leaves, with their pupae found close to the mid-rib. The presence or absence of mite predators can help you determine the best management strategy moving forward.

Predatory adult Stethorus
Predatory adult Stethorus beetles on a banana leaf

If healthy predator populations are detected then your consultant may advise continued weekly monitoring. You may also consider boosting the number of natural predators by releasing the predatory mite Californicus as a hot-spot treatment if only certain parts of the paddock are having mite flares.

High level mites present
Mites on the underside of banana leaf, adults visible to the naked eye

In addition to an overall damage assessment, it is also important to take note of the youngest leaf the mites are present on. In general, mites will move up the plant to the younger leaves, particularly as the population grows. By monitoring the movement of mites, decisions about the implementation of control practices to reduce or prevent the severity of irreversible damage to new leaves can be made. In general, the greater the number of mites and the younger the leaves they attack, the more severe the infestation.

It’s important to monitor regularly as spider mite populations can increase rapidly under favourable weather conditions (hot and dry). Therefore, always consider weather conditions before making management decisions. Rain and wet weather will help to keep spider mite populations down. If population levels are high, one rain event may not be enough to reduce spider mite populations sufficiently.

If you have high levels of damage (category 3) and spider mites are present on newly emerged leaves then a miticide treatment will be required to gain control of the population. Click here to view the chemical information below and talk to your consultant for specifics.

Download this information as a factsheet

For more information contact

The Better Bananas team
Department of Agriculture and Fisheries
South Johnstone
Email betterbananas@daf.qld.gov.au 

 
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.

Managing spider mites

Posted on by Better Bananas

Managing spider mites

Causes of mite flares

Broad spectrum insecticides (pesticides), such as bifenthrin, are one of the major causes of mite flares because they remove the beneficial predators that are providing background pest control. The use of such chemicals is not recommended.

Other factors likely to increase the potential for a mite problem include:

Causes of mite flares
Other factors likely to increase the potential of a mite flare

Management options

Avoiding the situations mentioned above will greatly contribute to managing spider mite populations. Click on the links below to read more on other activities that will assist include: 

For more information contact

The Better Bananas team
Department of Agriculture and Fisheries
South Johnstone
Email betterbananas@daf.qld.gov.au 

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.

Grower case study – protecting crowns improves fruit quality for Sellars Bananas

Posted on by Better Bananas

Protecting crowns improves fruit quality for Sellars Bananas

Anne Rikini and Naomi Brownrigg of Sellars Bananas. Naomi is happy with the results of using a post-harvest fungicide for controlling CER.

Sellars Bananas are renowned for producing premium quality bananas. However, frustratingly, even when supplying the best quality fruit at the farm gate, fungal organisms can wreak havoc with consignments down the supply chain. This has been the recent experience of Sellars Bananas and feedback from market agents is, they are not alone.

Crown end rot (CER) is caused by several fungal species and symptoms develop on the cut surface of the crown. Symptoms can differ in terms of severity depending on the causal fungal organisms present. Less severe damage includes superficial white/fluffy fungal growth on the cut surface. These symptoms rarely progress into the fingers of the fruit or affect eating quality (Figure 1). However, the more severe form of CER, commonly known as Chalara results in a black rot that extends from the crown into the fruit stalk and into the fingers, severely impacting fruit quality (Figure 2).

Feedback from the market is that CER continues to be a problem and symptoms start to develop as the fruit is ripened. It is hard to pick up before fruit is sent to retailers as not all cartons may be affected, and it may only impact one or two clusters across several cartons in a consignment. The good news is, there are post-harvest fungicides registered for use in bananas that can control CER.

Naomi Brownrigg from Sellars Bananas shares their experience with the problem and what they have put into place to manage it.

Figure 1: CER symptoms showing superficial white/fluffy fungal growth on the cut surface. This rarely extends into the fingers or affects the eating quality.
Figure 2: Symptoms of Chalara in Cavendish bananas. Black rot extends from the crown surface into the fingers, severely affecting fruit quality.
Figure 2: Symptoms of Chalara in Cavendish bananas. Black rot extends from the crown surface into the fingers, severely affecting fruit quality.
Figure 2: Symptoms of Chalara in Cavendish bananas. Black rot extends from the crown surface into the fingers, severely affecting fruit quality.
Figure 2: Symptoms of Chalara in Cavendish bananas. Black rot extends from the crown surface into the fingers, severely affecting fruit quality.
Figure 2: Symptoms of Chalara in Cavendish bananas. Black rot extends from the crown surface into the fingers, severely affecting fruit quality.
Figure 2: Symptoms of Chalara in Cavendish bananas. Black rot extends from the crown surface into the fingers, severely affecting fruit quality.

Chalara, a recent issue for Sellars Bananas

The symptom of superficial fungal growth on the cut surface of crowns has always been a minor problem from time to time for Sellars Bananas, predominately in the summer months. Naomi became more concerned when she started to see symptoms of Chalara approximately 3 years ago, causing more significant damage to fruit quality. ‘We never thought we had to treat it until Chalara started to turn up. At first, it was just now and then in the winter months, and then it started to appear most weeks of the year over a period of 2 years,’ Naomi said. ‘If you have never seen Chalara, it’s like CER on steroids. It will quickly rot the fruit from the crown down once the ripening process begins. Not all cartons are affected, it may be only one or two boxes or some clusters in a single box.’

Good shed hygiene and the use of chlorine didn't fix the issue

Before implementing the post-harvest spray system, Sellars Bananas tried different practices to resolve the issue. ‘Initially, we tried sanitising the shed and used a high-pressure cleaner in all of the wet areas. Although it’s a good practice, it didn’t work,’ Naomi said. ‘We then tried an inline chlorinator that used chlorine tables, that also didn’t work. Finally, at the congress last year, I spoke to Kathy Grice and David East from the Department of Agriculture and Fisheries on the issue and they were pretty clear that the only way to control it was with a post-harvest spray. So, we set about implementing a post-harvest fungicide spray, using prochloraz that treats all the fruit on the wheel.’

The packing wheel required some family ingenuity

Naomi enlisted the expertise of her brother-in-law Mark Nissen to come up with a spray system that would work for their 3-tier banana wheel (Figure 3). Once they had designed the frame at the right height and angles, Mark welded the steel frame together. The next step was attaching the spray system. ‘We set up a spray rig with three nozzles, one for each tier on the wheel, and attached a 200 L Silvan tank to it with a spray unit (Figure 4),’ Naomi said. ‘The spray unit puts out 7 L/min and each nozzle puts out 300 mL/min. The pressure is regulated, and any excess chemical solution is returned to the tank.’ As per the label instructions we do not catch any of the solution from underneath the wheel once it has been sprayed on the fruit. We use the product Protak® and the label rate is 110 mL/200 L. For our operation, this means we are using 250 mL of Protak® each day.’

Tips for placement of spray booths:

  • Spray booth should be placed after the fruit wash.
  • Position spray nozzles and clusters to ensure the crown surface is sprayed (Figure 5).
  • Set the speed of the wheel or belt (trough systems) to allow a 30-second spray.
  • Position the spray booth at the furthest point possible away from packers and use spray shields to minimise spray mist (Figure 6).
  • Place spray booths in a well-ventilated area.

Have a trough instead of a wheel?
Many packing sheds have installed post-fungicide spray booths, spraying crowns after they leave the trough and before reaching packers.

Figure 5: Clusters are placed upwards on the wheel to ensure cut surface of crowns are treated.

Implementation didn't require changes to existing practices

No changes were required in terms of Sellar’s packing procedures. ‘We were already placing the fruit with the crowns up,’ Naomi said. ‘There seems to be no mist from the spray, as there is a protective shroud around the spray unit (Figure 6). We are using Protak®, so there is no smell, and our packers all wear gloves.’

The benefits outweigh the cost

All up the cost of the spray unit itself excluding labour, was approximately $2000. This includes the tank, pump, inverter, hoses, nozzles, connections etc. and steel for the frame. The only ongoing costs apart from electricity costs for the pump, is the chemical itself. ‘We average one litre of Protak per week and current pricing is $170/L,’ Naomi said. 

Although Chalara was the main reason for Sellars to implement a post-harvest spray, they believe the benefits have been substantial when it comes to overall fruit quality. ‘The difference it makes to the appearance of the crowns at the market is huge, you can store the fruit for longer knowing that the crowns are going to hold up which gives them options as to when the fruit gets sold,’ Naomi said. ‘You may think this is a bad thing, but if the crowns are not holding up, that fruit needs to be sold ASAP, sometimes at a discount. I have been told that buyers of our fruit are very happy with the results. I wish we had implemented it (spray system) years ago.’

Sellars’ market agent is also happy with the results and now sends Naomi photos of clean crowns since they have installed the post-harvest fungicide spray (Figures 7 & 8). 

If you would like more information on this case study or managing CER in bananas contact  DAF’s Banana Extension Team via email betterbananas@daf.qld.gov.au.

Figure 6: Protective shroud around booth minimises spray mist.
Figure 7: Sellars fruit showing clean crowns 11 days after post-harvest fungicide treatment.
Figure 8: Sellars fruit showing clean crowns 11 days after post-harvest fungicide treatment.

Thank you

Thank you to Naomi Brownrigg and the team at Sellars Bananas who provided their time and gave permission to use this case study for the benefit of the wider industry.

The application of post-harvest fungicides is the most effective management strategy.

Research led by Kathy Grice from the Department of Agriculture and Fisheries (DAF) has shown that post-harvest fungicide application is the most effective management strategy. At the time of publication products containing thiabendazole (e.g. Tecto®) and prochloraz (e.g. Protak®) are registered for post-harvest use in bananas.  Important screening work undertaken by DAF has shown that some of the organisms that cause CER are less sensitive to thiabendazole-based products, particularly in the coastal regions of Far North Queensland. These organisms remain more sensitive to products containing prochloraz.

The application method is different depending on what product you use.

Products containing thiabendazole (e.g. Tecto®) are registered for use as a dip. Whereas products containing prochloraz (e.g. Protak®) are registered for use as a non-recirculating spray system only.

Always check the APVMA website for the registration status of products before use and follow label directions.

More information

This case study has been produced as part of project BA19004 the National Banana Development and Extension Program which is funded by Hort Innovation, using the banana industry research and development levies, co-investment from the 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.

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 water-soaked shadowing
Sooty blotch
Sooty blotch
Sooty blotch damage in ripe fruit
Sooty blotch damage in ripe fruit
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
Sooty mould powdery growth
Sooty mould powdery growth
Sooty mould - when zoomed it is possible to see insect casts (aphids)
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
Fruit speckle affecting all fingers in cluster
Severe fruit speckle damage
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.

Yellow Sigatoka (leaf spot) General information

Posted on by Better Bananas

Yellow Sigatoka (leaf spot) Pseudocercospora musae

What is yellow Sigatoka and where does it occur?

Yellow Sigatoka is a fungal disease in bananas that causes leaf lesions and is commonly referred to as leaf spot. The fungal plant pathogen that causes the disease is Pseudocercospora musae.

Yellow Sigatoka occurs in all growing regions of Australia and is common in Far North Queensland, particularly during the wet season when conditions are warm and moist.

Figure 1 Advanced symptoms of yellow Sigatoka disease. It is important to remove leaves with visible spot prior to fungicide application, to reduce disease load and to ensure the longevity of fungicides used for management.

How does yellow Sigatoka impact banana production?

The lesions caused by the disease result in premature leaf death and reduces the plant’s ability to photosynthesize, impacting bunch size and delaying bunch filling. It also reduces the green life of fruit, causing mixed ripening which can restrict market access. 

If left uncontrolled or unmanaged (Figure 1), costs of deleafing and spraying increase and it can be difficult to identify other exotic leaf diseases such as black Sigatoka.

How does yellow Sigatoka spread?

The disease produces two types of spores, ascospores and conidia that spread by two main vectors, air and water.

Air movement within banana paddocks allows for easy dispersion of fungal spores (ascospores), allowing them to settle and infect new plants. These spores are most active in the wet season due to warm and moist conditions, causing tip spotting in younger leaves. Ascospores are responsible for the long distance spread of the disease due to dispersing in air currents.

Movement by water, such as rainfall or dew, moves conidia from higher leaves down the plant and onto suckers and causes line spotting on the leaf. Conidia infect new leaves of the same plant or neighbouring plants if the rain is wind driven.

What are the stages of yellow Sigatoka

Symptom development of yellow Sigatoka is broken up into five stages (Figure 2).

Stage 1: Yellowish green specks less than 1mm long. Generally, younger leaves are affected. Very hard to see with the naked eye.
Stage 2a: Specks develop into yellow streaks 3 to 4 mm long.
Stage 2b: Streaks darken to a rusty brown.
Stage 3: Streaks broaden to a spot, becoming wider with undefined margins.
Stage 4: Spots develop defined dark brown edges, the centre becomes sunken and occasionally has a yellow halo. Conidia are produced on stage 4 lesions. 
Stage 5: Sunken centre turns grey and is surrounded by dark brown/black border. Ascospores are produced on stage 5 lesions. 

Figure 2 Five stages of yellow Sigatoka symptom development.

How is yellow Sigatoka managed?

Yellow Sigatoka can be difficult to control in wet, moist conditions and should be managed with a combination of cultural and chemical controls.

Deleafing (Figure 3) is a major component of managing yellow Sigatoka that cannot be overlooked. Increased chemical application is unable to compensate for regular deleafing practices.

What cultural controls should I practice?

Controlling yellow Sigatoka is best managed through cultural control practices. Although labour intensive, they are necessary to keep fungal levels low within a canopy, especially during periods of high rainfall when the ability to aerial spray or mist is limited. 

Figure 3 Regular deleafing is critical for yellow Sigatoka control.

Deleafing is the most critical control method for managing yellow Sigatoka.

  • Deleafing removes infected leaves from the canopy and assists in keeping disease inoculum levels low. Deleafing is recommended once a single leaf on a plant has leaf spot lesions on more than 5% of the total leaf surface.

  • To prevent yellow Sigatoka infections, some growers practice intensive deleafing practices. This involves removing additional leaves, that are not yet showing visible signs of the disease, as the early stages can be difficult to detect with the naked eye. Bunched plants are an exception, as most growers only remove the minimum number of leaves. Tipping, which is only cutting out a proportion of the leaf with visible symptoms, is not recommended as the entire leaf would be infected.

  • Deleaf before spraying, as once yellow Sigatoka produces visible lesions (stage 3 onwards) neither systemic nor protectant fungicide applications are effective against those spots. Deleafing also assists in reducing the risk of fungicide resistance on your farm, and neighbouring farms.

  • Recent research suggests that the best deleafing practice is to go through frequently before the wet season to get inoculum levels low. This will improve spray efficiencies before the warm wet summer when yellow Sigatoka pressure is heaviest. In the wet season, deleafing can extend to every 6-8 weeks and during the dry season every 8-12 weeks, depending on disease pressure.

Other cultural practices

Other cultural practices, such as block design, are also important for managing the disease. Maximising airflow through a block will assist in creating conditions that minimise disease development. This includes the following considerations:

  • Avoid placing blocks close to waterbodies, such as dams, as it will only promote the disease due to the high humidity associated with them.

  • Lower density plantings are recommended to promote a drier microclimate.

  • Maintain good drainage to ensure water does not sit within interrows.

  • Reduce plant-to-plant contact by removing unnecessary suckers.

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Yellow Sigatoka – General information

More information

Videos

Overview of leaf spot diseases and their impact

Yellow Sigatoka – Life cycle and how it spreads

Yellow Sigatoka – Management tips for growers

For more information contact:

The Better Bananas team
Department of Agriculture and Fisheries
South Johnstone
13 25 23 or email betterbananas@daf.qld.gov.au

This information has been produced as part of the National Banana Development and Extension Program, funded by Hort Innovation, using the banana 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.
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