Panama TR4 variety screening trial

Contributions by:
Sharl Mintoff1, Samantha Cullen1, Chris Kelly1, Maxine Piggott1 and Jeff Daniells2
1Northern Territory Department of Industry, Tourism and Trade, Darwin, NT
2Queensland Department of Agriculture and Fisheries, South Johnstone, QLD

Main trial results (plant and first ratoon)

Disease assessments

Disease assessments were carried out fortnightly once external symptoms became apparent in a susceptible variety. Assessments included noting the appearance of external disease symptoms and internal symptoms at plant death or harvest. Disease performances of a particular variety were given a score and grouped into one of the following categories:
Highly resistant (HR) – No disease symptoms were observed within the crop cycle and may not show symptoms under high inoculum pressures.
Resistant (R) – Plants normally show no signs of infection in the presence of the pathogen. However, under high inoculum pressures low amounts of symptoms or losses may occur.
Intermediate (I) – Plants which can withstand some infection and suffer low losses under natural infestation conditions, with most completing their crop cycle. However, its susceptibility or resistance can be highly dependent on the inoculum pressure already present. With the appropriate crop management or environment to lower the inoculum levels, these should be commercially viable. 
Susceptible (S) – More than 50% of plants show symptoms and/or killed due to pathogen infection. 
Very susceptible (VS) – Majority of plants (more than 70%) showed severe symptoms, most of which died due to TR4.

Results

Interestingly there appeared to be a reduction in disease severity observed across the first ratoon crop compared to the plant crop, with dramatic shifts occurring for a couple of varieties (Table 1). 

Highly resistant
CIRAD 03 and CIRAD 04 retained their resistance seen in the previous crop cycle continuing to be classified as highly resistant into the first ratoon. Dwarf French Plantain moved up into this category with no disease symptoms noted in the ratoon crop.

Resistant

Varieties Asia Pacific No. 1 and CIRAD 05 both displayed low incidences of TR4 infection in the first ratoon moving them down into the resistant category. GCTCV 105 and GCTCV 217 (Figure 1) both moved up into the resistant category after displaying a slight reduction in disease development in the ratoon crop. The resistant reference Goldfinger remained in this category.

Intermediate

Asia Pacific No. 3 moved down into this category due to an increase in plants infected with TR4 in the ratoon crop cycle. CIRAD 06 and High Noon, showed a dramatic reduction in the number of affected plants in the ratoon crop moving them up from very susceptible (in the plant crop) into the intermediate category.

Susceptible and very susceptible

Varieties that were deemed susceptible within the first ratoon crop cycle included Hom Thong Mokho, Pisang Ceylan, PKZ and the CJ19 Selection. The intermediate reference variety Formosana displayed an increase in disease severity in the first ratoon crop and as a result was moved down into the susceptible category. The susceptibility of the very susceptible reference variety Williams did not change.

Table 1 Resistance rating of trial plants in plant crop and first ratoon

HR = highly resistant, R = resistant, I = intermediate, S = susceptible, VS = very susceptible

GCTCV 105
GCTCV 217
Williams

Figure 1 Representative resistance for certain Cavendish varieties exposed to TR4 in the first ratoon. Williams displayed prominent disease symptoms with leaf yellowing, necrosis and eventual death. The majority of plants for the resistant varieties GCTCV 105 and 217 displayed no symptoms during first ratoon. Photos courtesy of Sharl Mintoff.

Generally, the focus of the NT screening trials is to identify resistant varieties, especially those that display similar or better resistance than Formosana, as it is used as the benchmark for the lowest acceptable level of resistance. In this trial eight varieties demonstrated better resistance than Formosana, which include Cavendish and CIRAD lines.
The Cavendish selections Asia Pacific No. 3 and GCTCV 217 both performed better than Formosana against TR4 and have also performed fairly well agronomically in north Queensland, so they are being considered for on-farm pre-commercialisation trials in 2022. There were two other Cavendish with intermediate or resistant reactions: the Asia Pacific No. 1 plants were all tissue culture offtypes (very slow and low yielding), whilst the fruit of GCTCV 105 was too short in South Johnstone trials, with significantly less fruit in the currently required size range for market. 
The continued good performance of Dwarf French Plantain against TR4 is encouraging for the few commercial producers of this type of niche variety. The CIRAD lines 03, 04 and 05 all had outstanding resistance against TR4 across the 2 crops which is very encouraging for the French breeding program. However, growers must understand that these are not Cavendish and so the fruit they produce does not slot readily into the current market requirements. The plants are taller making them more difficult to manage and subject to greater wind damage. 
Although apparent ‘recovery’ occurred in some varieties within the first ratoon crop, a degree of caution is required when interpreting these results, particularly in the case of CIRAD 06 and High Noon. Although the results of those two varieties are very interesting, this would need to be investigated further to determine how repeatable such a recovery is, and whether indeed, it would continue into later ratoon crops. 
This research has been funded as part of the project Improved Plant Protection for the Banana Industry (BA16001), which is funded by Hort Innovation, using the banana research and development levy, co-investment from the Department of Agriculture and Fisheries and the Northern Territory Department of Industry, Tourism and Trade and contributions from the Australian Government. Hort Innovation is the grower-owned, not-for-profit research and development corporation for Australian horticulture.

South Johnstone field walk

South Johnstone field walk

The latest research into new varieties, banana desuckering and nutrient rates was on display during a field walk at the South Johnstone Research Facility in July 2021.

Over 50 banana growers and industry stakeholders attended the event which was organised by the National Banana Development and Extension program.

The field walk featured:

  • A tour with Jeff Daniells through the new variety trial where the team are evaluating a suite of banana varieties. Growers had the opportunity to see firsthand plant crop bunches of these varieties, which included Lady Finger types, some CIRAD varieties, High Noon as well as a few Cavendish varieties, GCTCV 106 selection, Asia Pacific #1, Formosana and Williams. A video of Jeff’s presentation is available below.

  • Research updates from Shanara Veivers and Nandita Pathania on desuckering of tissue culture plants for improved productivity. The research showed that plants that were desuckered twice in the plant crop (12 weeks after planting and at bunch emergence) produced larger bunches in both the plant and first ratoon crops compared to plants that had only been desuckered once (at bunch emergence). The largest difference being in the first ratoon crop where bunches were 23.8% heavier. Keep an eye out for an update on the Better Bananas website coming soon that will detail more information about this research. A video of Shanara’s presentation is available below. 

  • An update from Curtis Lanham and Rebecca Murray on the Nitrogen and Phosphorus rate trials currently being run at the research station which are monitoring yield and nutrient losses.

Jeff Daniells showing field walk participants through the new variety evaluation trial

ABGC’s Sonia Campbell attended the event and captured two of the presentations. Click below to watch.

Extension events are funded as part of the National Banana Development and Extension Program (BA19004). This project is funded by Hort Innovation, using the Hort Innovation 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.

Agronomic evaluation of new varieties – South Johnstone (planted September 2018)

Plant crop observations and results (Trial planted September 2018)

Harvesting of the plant crop commenced with Williams in mid-May 2019 — less than 8 months after planting! However, several varieties were much slower in development and harvest of the plant crop continued until the end of the 2019 calendar year. Yield and plant characteristics recorded for the plant crop is available . It is worth noting when looking at these initial observations that this is the first time many of these varieties have been grown in Far North Queensland and the number of plants of each variety included in the screening is quite small. It is also important to keep in mind seasonal effects on the trial’s long harvest period of May to December. For example, winter bunch filling will be slower than summer bunch filling.

Promising varieties based on plant crop observations

All of the Taiwanese Cavendish selections available in Australia are included in this trial. These selections were typically two to five months slower than Williams in the plant crop, however several had heavier bunches. When taking into account bunch weight relative to time taken, there are some promising results with two new selections, Asia Pacific #3 and GCTCV 217 having comparable results with Williams. Two Formosana (GCTCV 218) selections have shown promising results with comparable yields to Williams.

GCTCV 217 plant bunch
GCTCV 218 (Formosana) Selection plant bunch
GCTCV 218 (Formosana) Selection plant bunch

Other Taiwanese varieties yielded from 77 to 94% compared to Williams in the plant crop. Some had significantly shorter fruit, as indicated by the percentage of fruit in the 22-26 cm size category. Depending on the time of year fruit are harvested, this could be an advantage or a disadvantage in achieving more fruit in the desired size range for the market compared to Williams. Several of the Taiwanese varieties were taller than Williams.  

Rahan Meristem Cavendish selections

Bunches of the Rahan Meristem Cavendish selections have been impressive, with all four selections being characterised by heavy bunches, long fruit, and good hand separation in the bunch which should help minimise fingertip scarring.

Gal and Jaffa were the only varieties in the trial that yielded significantly higher (per unit time) than Williams. These selections have not been tested against Panama disease TR4 but are not expected to have any resistance. 

These selections are owned in Australia by Rahan Meristem and were made available to some growers as part of on-farm evaluations towards the end of 2020.

Rahan Meristem Gal plant bunch
Rahan Meristem Jaffa plant bunch

Other varieties

The dwarf selections of Cavendish, Brier and Dwarf Cavendish both yielded well. However, fruit of Dwarf Cavendish had substantially shorter fruit than Williams. 

CIRAD hybrids only yielded 52% to 58% to that of Williams and were 12 to 46% taller than Williams in the plant crop. Their leaf petioles seem quite brittle and under wind often snapped. Fruit of the four hybrids have been tasted by staff at South Johnstone – CIRAD’s 03 & 05 were particularly liked whilst 04 and 06 were probably too fragrant. 

A repeat evaluation is underway, as part of the new evaluation established at South Johnstone in 2020 for a few varieties which had a high incidence of tissue culture offtypes in the 2018 evaluation. 

CIRAD 05 plant bunch
Brier plant bunch
Some of the leaf disease resistant CIRAD hybrids, including CIRAD 03 pictured, have been well received by DAF staff at informal tasting sessions

Results

More information

This research has been funded as part of the project Improved Plant Protection for the Banana Industry (BA16001), which is funded by Hort Innovation, using the banana research and development levy, 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.

Agronomic evaluation of new varieties – South Johnstone (planted September 2018)

The first ratoon crop is now completed in the variety trial at South Johnstone, and the results are encouraging with:

  • The TBRI Cavendish selection Asia Pacific #3 showing comparable yields and fruit length to Williams over the two crop cycles, combined with Panama disease TR4 resistance much better than Formosana in the Northern Territory trials. 
  • Continued good performance of the four Cavendish selections from Rahan Meristem with yields and finger length equivalent to Williams, with at least two of the selections being significantly shorter in stature.
  • The Dwarf Cavendish selection Brier, from the Canary Islands, having yields and fruit length equivalent to Williams while being significantly shorter in stature. 

First ratoon crop observations and results (Trial planted September 2018)

Most of these selections originate from international breeding programs (Taiwan, Israel, and Guadeloupe) and are being grown for the first time in Australia after clearing quarantine. Some have so far demonstrated promise, whilst the agronomic characteristics of others have been less desirable. A notable spread of cycle time between varieties was already observed in the plant crop. This meant that some of the early second ratoon bunches of the quicker cycling varieties had already begun to be harvested before all the first ratoon bunches had been completed for the much slower cycling ones. As a result of this, some varieties were experiencing quite different seasonal conditions during the period of bunch development compared to others.

The preliminary results from this investigation are a useful first look, but pre-commercialisation trials for any of the better varieties will tell more accurately how these results reflect their broader performance. The data discussed next is displayed in Table 1.

Taiwanese Cavendish selections

The nine TR4 resistant selections from Taiwan took between 19.6 and 23.7 months to reach ratoon one harvest from planting, which was considerably slower than the 17 months taken by the industry standard Williams. The slower cycle times and lower bunch weights resulted in cumulative yields (plant + ratoon 1) 63–82% of that of Williams. The only exception was Asia Pacific #3, which had a comparable yield to Williams. The high cumulative yield of Asia Pacific #3 combined with its TR4 resistance, which was much better than Formosana in the NT trials, is very encouraging. This makes it a contender for inclusion in future pre-commercialisation trials.

The varieties GCTCV 119, 215, 217 and 247, along with Asia Pacific #3, were all significantly taller than Williams. However, rather than breaking over from wind damage, losses were typified by snapping at the point of connection of the prop to the pseudostem. It was a particular issue for Asia Pacific #3, where just over half the datum plants snapped at the prop or the bunch fell out at the throat. The same fate occurred to 38 and 31% of the GCTCV 217 and 119 plants, respectively. GCTCV 247 and 215 had very few bunches affected in this way. 
Perhaps if the varieties were grown in double rows supported by twine then losses would have been lessened (for the current single-row configuration, propping is done using metal wire affixed to wooden stakes inserted towards the top of the pseudostem).

A first ratoon bunch of Asia Pacific #3. This variety demonstrated good TR4 resistance in NT trials and its cumulative yield (plant + R1) was comparable to Williams
Snapping at the prop appeared to be a particular issue for Asia Pacific #3, GCTCV 217 and 119, and the CIRAD hybrids

Rahan Meristem Cavendish selections

As was the case in the plant crop, the four Rahan Meristem Cavendish selections (Jaffa, Gal, Adi 9001 and Adi 9168) have continued to perform well in all respects compared to Williams in the first ratoon. It is noteworthy that Adi 9001 (2.7 m) and Adi 9168 (2.3 m) were both significantly shorter than Williams (3.1 m) but there were no issues with choking. Several commercial farms have begun growing these varieties on a small-scale due to their promising agronomic qualities.

A first ratoon bunch of Rahan Meristem cavendish selection, Jaffa
In the first ratoon Adi 9168 plants were again significantly shorter than Williams and cumulative yield has been comparable

Guadeloupe CIRAD hybrids

It took around five months longer for CIRAD 04 to reach first ratoon harvest compared to the other three CIRAD hybrids . The cumulative yields of the CIRAD hybrids were slightly better than for the plant crop but were still only 57 – 66% of that of Williams. Plants remained significantly taller (11 – 31%) than Williams. Their brittle pseudostems were prone to snapping, and their long, narrow leaf stalks readily bent over leading to much reduced leaf area. Like some of the Taiwanese selections, these too were prone to snapping at the prop.

A first ratoon bunch of CIRAD hybrid, CIRAD 05
The CIRAD hybrids, including CIRAD 04 pictured, performed poorly. The plants are much taller than Williams and leave break readily

Other varieties

A first ratoon bunch of the dwarf Cavendish selection, Brier

The two dwarf selections of Cavendish, Brier and Dwarf Cavendish, had comparable cycle times and bunch weights to Williams. And as was the case in the plant crop, Dwarf Cavendish had shorter fruit than both Brier and Williams (indicated by the percentage of fruit in the 22–26 cm size category).

Results

More information

This research has been funded as part of the project Improved Plant Protection for the Banana Industry (BA16001), which is funded by Hort Innovation, using the banana research and development levy, 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.

Subtropical banana research and resources

This section of our website has been developed to provide subtropical banana growers with information and resources developed specifically to address the production challenges faced in their regions.

About the subtropical industry

Australia’s subtropical banana growing regions extend from just south of Coffs Harbour in northern New South Wales up to Bundaberg in southern Queensland, and in the west includes the production region of Carnarvon. Combined, subtropical banana production accounts for 6% (New South Wales 4% and Carnarvon 2%) of the national industry, with a mixture of both Lady Finger and Cavendish banana varieties predominately grown.

Unlike the tropical growing regions in the north, subtropical banana growers are impacted more by the seasonal influence of cold weather and cold-induced plant stress. Relatively low rainfall in these subtropical regions during winter in combination with the cold temperatures can exacerbate the effects of cold conditions.

For subtropical growers in New South Wales and Queensland, steeper terrain also proves challenging in terms of the mechanisation of farming systems for increased efficiency and limits the use of irrigation. These constraints can increase the difficulty of maintaining consistent fruit quality throughout the year and result in a decrease in overall yield. 

Presence of Panama disease in subtropical growing regions

The subtropical growing regions of New South Wales, Queensland and Western Australia are also affected by Panama disease caused by the fungus Fusarium oxysporum f.sp. cubense. 

Panama disease race 1 is present in all subtropical growing regions and infects Lady finger, Ducasse and Sugar banana varieties but not Cavendish bananas. Race 2 has been detected in northern New South Wales and infects cooking bananas such as Bluggoe and Blue Java. Panama disease subtropical race 4 is also present in all subtropical growing regions and infects most banana varieties including Cavendish cultivars, particularly after being exposed to a period of environmental stress. Subtropical race 4 is less virulent than Panama disease tropical race 4, which is under strict quarantine in the tropical growing regions of the Northern Territory and Far North Queensland. It is important that all banana growers implement good on-farm biosecurity measures to minimise the risk of further spread of the disease and potential introduction of Panama disease tropical race 4.

Banana bunchy top virus

Northern NSW and South East Queensland is also actively managing Banana Bunchy Top Virus (BBTV), a serious plant pest that is regulated in both states. BBTV is spread from plant to plant by the banana aphid Pentalonia nigronervosa. Banana plants infected with BBTV rarely produce fruit. If a bunch is produced it is usually small, deformed and unmarketable. Industry continues to invest in a National Banana Bunchy Top Virus program that runs in South East Queensland and Northern New South Wales to contain and control the disease within the known bunchy top zone and prevent its spread to other production regions. Click here for more information.

Research and resources

Subtropical banana resources

Resource collection

(2021) NSW DPI - Banana soil and tissue analysis interpretation guidelines
(2021) NSW DPI - Panama disease race 1 (recorded presentation)
(2020) NSW DPI - Banana quality issues poster
(2017) DAF - Banana best management practices for on-farm biosecurity
(2016) NSW DPI - Subtropical banana nutrition
(2008) NSW DPI - Banana growing guide Cavendish bananas
(2008) NSW DPI - Soil and water best management practices for NSW banana growers
(2008) NSW DPI - Banana growing basics for NSW
(2004) DAF - Subtropical banana information kit

Images of Banana rust thrips damage

Images of Banana rust thrips and damage caused to fruit

Adult Banana rust thrips and larva. Note the adult has a distinct black line formed by the folded wings and the two eye-like patches over the thorax
V-shaped rust markings on the upper pseudostem indicate the presence of high Banana rust thrips populations
Check under leaf petioles for adult thrips and larva. Insert shows white larvae found under leaf petioles
Early development of Banana rust thrips damage showing faint smudge-like mark
Banana rust thrips damage between the fingers where two adjacent fingers touch
Severe Banana rust thrips damage showing skin cracking
Severe Banana rust thrips damage on mature hand of fruit

More information

Click here for more information on Banana rust thrips.

Subtropical banana soil and leaf interpretation guidelines

Plant nutrition for subtropical banana production

In order to maximise banana productivity and yield, whilst increasing resilience to pests and diseases, it is necessary to get plant nutrition right. Soil and tissue analyses are vital for monitoring soil fertility and plant nutrition. Regularly testing soil and tissue nutrients, and tracking changes in nutrient over time, is essential for developing an accurate and appropriate fertiliser program that delivers the nutrients needed at the right time and can result in efficient and sustainable fertiliser use. It also allows soil fertility issues to be identified early and provides an opportunity to correct them before they begin to affect productivity. It is not possible to achieve this without correctly interpreting the information gained from soil and tissue nutrient analyses.  However, the results reported from soil and tissue analyses can often be confusing and include irrelevant information, making their interpretation challenging. The NSW soil and leaf analysis interpretation guidelines for bananas has been developed to assist with the interpretation of soil and tissue tests so you can make sure your bananas are getting the nutrient they need. 

Download a copy of the guidelines and other resources

For more information contact:

The Better Bananas team
NSW Department of Primary Industries – Industry Development Officer, Tom Flanagan – 02 6626 1352
Department of Agriculture and Fisheries – Banana Extension Team, South Johnstone – 07 4220 4177
or email the team at: betterbananas@daf.qld.gov.au 

The NSW soil and leaf analysis interpretation guidelines was funded by the New South Wales Department of Primary Industries.

Banana rust thrips – monitoring and control

Banana rust thrips Chaetanaphothrips signipennis

Monitoring and control options

Monitoring

Rust thrips can occur on unbunched plants and their presence can easily be determined by monitoring established plantations fortnightly throughout the year. New plantings should be inspected prior to bunching in order to determine both the presence and severity of rust thrips infestations so that control measures, if required, can be carried out before fruit damage occurs.

Under heavy infestations, rust thrips can produce characteristic V-shaped rust-coloured markings on pseudostems (Figure 1) as a result of their feeding where the leaf petiole meets the pseudostem. If these markings are observed, the presence of thrips should be confirmed by gently pulling the leaf petioles away from the stem (Figure 2) and inspecting these sites with a 10x hand lens. In addition, it’s advisable to occasionally lift a number of bunch covers and inspect the developing fruit to ensure no thrips or damage are present. If damage has occurred, further damage can be prevented by additional insecticide application, taking care to comply with withholding periods in accordance with the label.

Figure 1 - V-shaped rust markings on the upper pseudostem indicate the presence of high rust thrips populations

Damage to fingers can range from faint smudge-like markings through to the characteristic slightly red/brown damage known as ‘rust’. Special attention should be paid to those fingers which are closely pressed together as this is where the thrips prefer to feed and shelter.

Control options

Chemical

Chemical control can be directed at both the soil-dwelling pupal stage as well as the adults and larvae on the fruit and plant. Please ensure to always check the Australian Pesticides and Veterinary Medicines Authority (APVMA) website to confirm registration of chemical products before use. 

Soil/plant treatments: Apply registered insecticide (e.g. bifenthrin, imidacloprid) as per label directions (e.g. pseudostem treatment, band treatment method). Ensure ground treatments achieve good cover of both the ground around the base of the pseudostem and up the base of the pseudostem as per the label. Treatments aimed at banana weevil borer that are applied to the soil or pseudostem will also provide temporary control of rust thrips. Treatments applied in September/October for weevil borer should provide partial protection, depending on the product used, during November/December and into the early part of the following year. 

Figure 2 - Check under leaf petioles for adult thrips and larva. Insert shows white larvae found under leaf petioles

Fruit treatments: Bell injection is an important component of rust thrips control on the bunch. Correct and timely application is vital for effective control. Apply a registered insecticide (e.g. acephate, spinetoram) as per label or permit directions to the bell in an upright vertical position. Ensure the injector is calibrated and used correctly. 

Bunch spraying/dusting at bagging is also an important measure to control rust thrips.  Apply a registered insecticide (e.g. chlorpyrifos, spinetoram) as per label or permit directions to the bunch. Ensure the bunch spray/duster is calibrated and used correctly. Bifenthrin impregnated bunch covers can also be used instead of applying insecticides to the bunch as dusts or sprays.

Insecticide resistance can compromise the effectiveness of insecticides, therefore adhering to the label and or permit directions is essential. Endeavour to use chemicals with differing modes of action to minimise the possibility of resistance developing.

Monitoring is important to assess that the applied treatment has been effective. 

Cultural

Intact bunch covers (which cover the full length of the bunch) do provide some protection if applied very early. These cannot be relied upon to fully protect the fruit, particularly during severe infestations. Regular checking of fruit under the bunch covers is essential to ensure that damage is not occurring. Ensure treatments are applied immediately after detection to prevent further damage. 

Biological

There are currently no specific predators identified which provide a commercial level of control. General predators such as lacewings and ladybird beetles may exert some control of rust thrips on the plant, and ants may be effective in removing some of the pupae in the soil. 

For more information contact:

The Better Bananas team
Department of Agriculture and Fisheries
South Johnstone
07 4220 4177 or 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 updated 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 rust thrips – general information

Banana rust thrips Chaetanaphothrips signipennis General information

Occurrence

Banana rust thrips is a serious and frequent pest of bananas and has been since they were first grown in Queensland. Damage occurs in all areas but is more severe in bananas grown in well-drained red soils.

Seasonality

Rust thrips can damage fruit throughout the year however, the period from November to April is the period of greatest activity. Experience has shown that unusually dry periods during November and April encourage heavy build-ups of thrips and subsequent damage. Wet conditions are thought likely to cause high mortality of the soil-dwelling pupal stage, either directly from drowning or by encouraging the development and spread of diseases.

Figure 1 - Adult banana rust thrips and larva. Note the adult has a distinct black line formed by the folded wings and the two eye-like black patches over the thorax

Description and life cycle

The extremely small eggs are inserted by the female just below the surface of the fruit or other plant tissues. The small (0.5–1.0 mm long) white, slender larvae do not have wings and can be seen moving when areas of infestation are exposed by separating touching fruit. Larvae can also be seen moving on the stem of the plant by pulling back the edge of leaf sheaths. When fully developed, the larvae drop to the ground and pupate just below the soil surface, approximately 30 cm from the base of the plant and suckers. The white pupa is about 1mm long and can be very difficult to find. 

Figure 2 - Life cycle of banana rust thrips in summer months takes approximately 28 days to complete and can be up to 90 days in cooler winter months

The adult has small feather-like wings and is a slender (1–1.5 mm) straw-coloured insect. The wings are fringed with a line of dark scales and, when at rest along the body, these scales form a characteristic black longitudinal line running the length of the abdomen. Two eye-like dark patches at the base of the wings are a characteristic of rust thrips adults. These patches help distinguish them from the smaller males of banana flower thrips.

Damage

Fruit damage is caused during feeding by the larval and adult stages of the thrips. The damage first appears as a faint smudge-like mark (Figure 3) between the fingers in the area where two adjacent fingers touch (Figure 4). This later develops into typical reddish-brown ‘rust’ areas. Severe damage can result in skin cracking (Figures 5 & 6). 

The superficial damage does not reduce the fruit eating quality. However, affected fruit can be downgraded or rejected, depending on the severity of damage and the current market supply conditions. 

Note: Rust thrips damage should not be confused with maturity bronzing, which produces a rusty, reddish discolouration on the fingers. While it appears similar to rust thrips damage, maturity bronzing occurs on the exposed outer curve of the fruit and is not confined to areas where fingers are touching.

For more information contact:

The Better Bananas team
Department of Agriculture and Fisheries
South Johnstone
07 4220 4177 or 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 updated 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.