Spider mites – life cycle and behaviour

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Spider mites

Life cycle and behaviour

Both the banana spider mite (Tetranychus lambi) and the two-spotted mite (Tetranychus urticae) are often simply referred to as ‘spider mites’. Both are common pests of a broad range of crops and are widely distributed.

The life cycle and appearance of the banana spider mite and the two-spotted mite are similar. Both mites are typically found on the underside of leaves, only being present on the top side in very high infestations. The main distinguishing feature between the two types of mites is that high populations of the two-spotted mite are always associated with webbing (similar to spiders), while this is absent in infestations of the banana spider mite. Webbing occurs near mite colonies, typically on the underside of the midrib or in severe infestations, down the leaf veins. The two-spotted mite is more commonly found on bananas in South-East Queensland and northern NSW. By comparison, the banana spider mite predominantly is in Far North Queensland and is also identifiable as it is more straw coloured and lacks spots.

The life cycle of the mite (red arrows indicate parts of the plant affected)

The straw-coloured or greenish adult banana spider mites are usually less than 0.5mm in length and are best seen with the aid of a magnified (10X) hand lens. Under good light, the eight-legged adults have a spider-like appearance that can just be made out with the naked eye.

The very small transparent to yellow, spherical eggs are laid singly on the leaf surface and, upon hatching, pass through two nymphal stages before becoming adults. In hot conditions, the life cycle can be as short as seven to ten days.

Adult spider mite with eggs
Adult spider mite and its spherical eggs. Note the dark leaf tissue, an indication of dead leaf cells caused by mite feeding

By comparison, the adult female of the two-spotted mite (T. urticae) lives two to four weeks and can lay several hundred eggs during her life.1 Their quick life cycle and the ability of females to produce many eggs, can mean populations build rapidly if conditions are favourable.

Spider mites mainly use wind and small spun lines of web to migrate. The two-spotted mite is known to travel in winds as low as 8 km/h but prefers stronger winds.2 Mites also have the ability to move by walking on or short distances between plants2. Spider mites can migrate at any time, tending to move on when their populations become high, predators become abundant or the quality of food sources declines.

References

  1. Florida Department of Agriculture and Consumer Services, Division of Plant Industry 2009, University of Florida, viewed 17 January 2022, https://entnemdept.ufl.edu/creatures/orn/twospotted_mite.htm#top
  2. Seeman, O, Beard, J 2005, National Diagnostic Standards for Tetranychus Spider Mites, Plant Health Australia, Canberra

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.

Banana weevil borer – monitoring

Posted on by Better Bananas

Banana weevil borer Cosmopolites sordidus

Monitoring

Adult banana weevil borer activity increases during warm and/or wet weather and decreases during cold and/or dry conditions. Periods of greatest adult activity are in spring (September-October) and autumn (March-April). If blocks are suspected of infestation, trapping should concentrate on these times to determine whether chemical treatments are needed or not. In addition, it is advisable to set traps prior to a new planting or during the fallow period. This is to ensure that any banana plant material has decomposed entirely, eliminating the possibility of any remaining adult banana weevil borers being present in residues that might affect the new crop.

If infestations are suspected adult banana weevil borer monitoring should be carried out every month, except during the colder months when the time frame can be extended to six weeks. Banana weevil borer numbers at baits placed during adverse conditions may not accurately reflect actual adult population levels, as it has been shown that only 5-15% of the actual population will appear on baits under these conditions.

There are a few main methods of monitoring banana weevil borers, which are outlined below:

Bait trapping

Adult banana weevil borer numbers can be monitored by baiting (trapping). Baits are made by cutting a fresh pseudostem into slices about 10cm thick . The pseudostem material selected for making baits should ideally be taken from the lower portion of the stem of freshly harvested plants. One bait is placed close to the base of each plant, with one cut surface in full contact with the ground, and covered with leaves to prevent the bait from drying out. Twenty or more baits should be used in known hot spots to obtain a good indication of banana weevil borer numbers. The ground directly beneath the bait should be cleared of any weeds or plant material that can shelter adult banana weevil borers and hinder rapid checking of the baits. After three to four days, the baits are turned over and the adult banana weevil borers are counted (Hint! Look for banana weevil borers on the ground where the bait was resting as well as the base of the bait in contact with the ground).

Adult banana weevil borer numbers are recorded from each bait and, knowing the total number of baits set and banana weevil borers counted, the average number of adults per bait can be calculated by dividing the total number of banana weevil borers by the number of baits set.

Banana weevil borer BWB bait trapping
Banana pseudostem placed near the base of a banana plant to trap banana weevil borer.
Banana weevil borer BWB bait trapping
Banana pseudostem covered with a leaf to prevent drying out.
Traditional pitfall trap that is used with pheromones. Here the lid has been removed to count the number of banana weevil borer’s present.

Pheromone trapping

Another option for monitoring is the use of pheromone-baited traps, which contain a substance (sordidin) that specifically attracts adult banana weevil borers. These baits attract both male and female banana weevil borers and can attract individuals up to 20m away from the trap, however, this efficiency is reduced by rainfall. Baits need to be replaced every 30 days, as lures run out (depending on lure concentration – read labels for specifics). Different types of traps are commercially available for growers.

Corn damage assessment

Larval damage can be assessed by rating the percentage of tunnelling in the corm of harvested plants.

The larger the area affected the higher the pressure of banana weevil borers. This monitoring is destructive and requires the cutting of plants, and is more encouraged as a monitoring tool to see how known infestations are responding to treatment, rather than a diagnosis of infestations.

Download this information as a factsheet

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 and Treverrow, N., Pearley D., and Ireland, G 1992 Banana weevil borer : a pest management handbook for banana growers. : NSW Agriculture, North Coast Region; NSW Banana Industry Committee; Horticultural Research & Development Corporation.
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.
Hort innovation logo

Silicon innovation trial

Posted on by Better Bananas

Using silicon fertilisers to improve Lady Finger tolerance to Panama disease race 1

By Steven Norman

Background

Fusarium oxysporum f. sp. cubense (Foc) race 1 (Panama disease race 1) has been present in the north of New South Wales from the Tweed region south to Coffs Harbour for several decades and has had a devastating impact on growers of susceptible varieties in these areas.

Considered endemic in NSW, Panama disease race 1 is widely distributed across the region and has made it extremely difficult for Lady Finger growers to continue to produce this variety. As there are no control options for Panama disease race 1, the only alternative is to switch to growing those varieties that are resistant.

NSW silicon trial
Silicon trial site, February 2023

About the trial

The trial location is within the Tweed Valley of New South Wales and was planted in December 2021. A complete cycle of planned silicon treatment application has been carried out in collaboration and support with the grower. A new round of treatments will begin in late November 2022. 

As most NSW growers agree, 2022 was a challenging year due to the extended wet and cold periods. A combination of the sub-optimal growing conditions and isolated severe weather events has significantly slowed the growth of the bananas within the trial. The slowed growth reduced the infection rate, resulting in a lag of external symptoms. Our ability to record adequate data for early interpretation has been delayed. As the hotter months begin and growth rates increase, our ability to make accurate observations has improved.

Samples were taken in late September 2022 of suspect disease in plant tissue across the trial. It has been confirmed that Panama disease race 1 has infected the plants uniformly within the trial. This is good news for the trial efficacy. Uniform infection is paramount to measuring the silicon application’s effectiveness and its potential to improve tolerance to Panama disease race 1.

Latest update

Until March 2023, no external symptoms of Fusarium wilt were present, including the non-treated treatments (no silicon applied) within the trial.

nsw infected corm
Infected corm tissue sample
Suspected infected psuedostem
Silicon treatments applied in the trial

More information will be made available as the trial progresses.

This trial is a joint initiative between the NSW Department of Primary Industries, Southern Cross University, the University of Queensland, Agripower Australia and the Australian Banana Growers’ Council.

NSW SPI
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.

Agronomic evaluation of new varieties South Johnstone screening trials (2022)

Posted on by Better Bananas
By Jeff Daniells and Katie Robertson

About the trial

Five new TR4 resistant Cavendish selections from Taiwan and eighteen TR4 resistant Cavendish from the Department of Agriculture and Fisheries’ mutagenesis program, were field planted at South Johnstone and are being assessed for agronomic performance. Some new Lady Finger types from Brazil are also included in a smaller subtrial.

New Variety trial dec 2022
The new Cavendish variety trial established at South Johnstone in December 2022.

Objectives

The Department of Agriculture and Fisheries imported new varieties as part of the ‘Improved plant protection for the banana industry’ project (BA16001) completed in 2021.  These varieties included some TR4 resistant Cavendish from Taiwan and various Lady Finger types from Brazil, which were released from quarantine in early 2022. Also during that project, 18 TR4 resistant Cavendish selections were made from the mutagenesis trials established earlier in the Northern Territory as part of the ‘Fusarium wilt Tropical Race 4 research program’ (BA14014).

The new trial at South Johnstone was field planted with these varieties in early December 2022. They will be evaluated for agronomic performance over two crop cycles as part of the project ‘New varieties for Australian banana growers’ (BA21002). This is a first look at many of these varieties to see how they perform under north Queensland conditions. In addition, preliminary taste panel assessments will be made.

In conjunction with this agronomic evaluation, several of these varieties are to be screened against TR4 in the Northern Territory to confirm their level of disease resistance. However, the banana freckle outbreak in the NT last year is contributing to delays in commencing this component of the broader work. The Lady Finger types will also be evaluated for Race 1 Panama disease resistance in an on-farm trial on the Atherton Tablelands.

Overview of varieties

There are five new Cavendish selections from Taiwan including Improved Formosana, which is reported as quicker cycling than standard Formosana and shorter in stature, and GCTCV 219 which has sweeter fruit.

There are eighteen Cavendish selections from DAF’s mutagenesis program.  They were derived from the already TR4 resistant CJ19 and GCTCV 215. The selections were made for improved agronomic characteristics, including plant stature, and having a cycle duration closer to Williams.

Ones to watch amongst the Lady Finger types from Brazil are SCS451, a selection of Santa Catarina Prata with tolerance to Race 1 Fusarium wilt, and the Sugar hybrid, Princesa. 

Observations and results

Observations and results are now available for:

Improved Formosana, a TR4 resistant Cavendish selection from Taiwan is included in the new trial (photo courtesy TBRI).

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.

Steven Norman

Posted on by Better Bananas

Steven Norman

From vineyard to banana patch

Steve is supporting the NSW banana industry, working in the National Banana Development & Extension project with growers in the Tweed Valley, Coffs Harbour and Nambucca regions.

Steven’s experience in agriculture spans over a decade in several agricultural industries. Most of his experiences are in winemaking and vineyard production. His past work involved vineyard floor management, soil preservation, and viticultural techniques to produce unique flavour profiles.

Steven Norman
Sub-Tropical Horticulture Development Officer
NSW Department of Primary Industries
Wollongbar Primary Industries Institute
Wollongbar

In 2021, Steven took up a position as an Extension Agronomist with Farmacist in conjunction with Queensland Farmers Federation. Based in Mackay, he assisted in research looking at alternate plant varieties within sugar cane fallow crops, multispecies interrow companion planting, and investigations into different ways to capture and measure sediment runoff.

Steven is passionate about horticulture and seeing solutions to problems being found.

‘I see myself continuing in a position where I can listen to growers, plan and collaborate with them to deliver solutions. My motivations will always be to improve social, economic and environmental aspects within my focused industries’. In his role Steven is also working with other industries in NSW including blueberries.

‘A focus will be understanding where the growers in NSW are having difficulties or better understanding their challenges’

Steven enjoys a good banana bread, and his favourite recipe includes maple syrup to give it that extra sweetness.

Carole Wright

Posted on by Better Bananas

Carole Wright

Number crunching to help researchers understand their trials

Carole Wright plays a vital role in many of the banana trials conducted by Department of Agriculture and Fisheries. She works with researchers in trial design and helps make sense of their data. As a biometrician she develops and applies mathematical or statistical theory and methods to collect, organise, interpret, and summarise data to provide insight and meaningful interpretation of results. Carole is based in Mareeba and has been involved in banana research since 2008. She has applied her biometry knowledge to analyse a 

Meet a researcher

vast range of banana research including variety trials, bunch pest trials, nutrient rate trials, soil biology trials and crop timing, just to name a few. Carole also works with other industries and is currently developing a model to predict the meat fullness of mud crabs using near-infrared spectroscopy.

‘I get excited when I find something unexpected in the data that the researcher wasn’t necessarily looking for.  I enjoy the variety of work that comes my way and the satisfaction of extracting interesting conclusions from the data that excites the researcher’, Carole said.

Carole grew up in Hastings, New Zealand and attended Waikato University in Hamilton, completing a bachelor degree and Masters of Computing and Mathematical Science.  She worked in agricultural research for 5 years, before returning to university to complete a PhD. Her doctorate involved developing an algorithm to generate resolvable row-column designs which are often used to evaluate large scale field trials. She worked in Victoria, Northern Territory and England, prior to moving to Far North Queensland in 2008.


Carole says she is not renown for her cooking but finds banana and bacon cooked on the BBQ delicious.

In her free time Carole enjoys scuba diving and always looks forward to minke whale season.

Why is Banana Bunchy Top Disease so hard to eradicate?

Posted on by Better Bananas

Why is banana bunchy top disease so hard to eradicate?

By Dr. Kathy Crew and Dr. John Thomas

Banana bunchy top disease (BBTD) occurs in many locations throughout northern NSW and southern Queensland. The disease was first recognised in Australia in 1913 and by the mid-1920s had devastated the Australian industry, which was based in this region at that stage, causing losses of 90 to 95% of production. The research work of Charles Magee at the time revealed that the disease was caused by a virus (banana bunchy top virus, BBTV) which was transmitted by the banana aphid and in infected planting material. He devised a successful control program which enabled the resurrection of the industry. His strategy of inspection, destruction of infected plants, use of clean planting material, and quarantine remains the basis of BBTV control to this day. 

However, despite the generally low incidence of BBTD in the region today, occasional flare-ups still occur, and the virus has rarely been eradicated from a district. Despite the low incidence in many subtropical plantations, the virus remains a potential threat to the banana industry. Why is this so?

BBTV symptoms in an infected plant. Symptoms include stunted, upright, “bunched” leaves with upcurled, yellow margins and discontinuous dark green lines/dots and dashes are visible on the underside of leaves when viewed with transmitted light. Photo: K.Crew, DAF.

In his research, Magee was only able to transmit the virus by aphids when they fed on a symptomatic leaf. Excellent subsequent epidemiological and computer modelling work by Rob Allen predicted that aphids were only likely to spread the virus after about four new leaves had been formed on the newly infected plant. This allowed enough time for the infected plant to develop symptoms and for the aphid vector to acquire enough virus to be infective. The BBTD control program is based on inspection intervals timed to allow the location and eradication of most infected plants within this window.

The strategic levy investment project “Understanding the role of latency in Banana Bunchy Top Virus symptom expression” (BA19002) is part of the Hort Innovation Banana Fund. As part of BA19002, we have been studying an outbreak of BBTD on a plantation in northern NSW where the disease persists at a high level, despite the control program.

The banana aphid, Pentalonia nigronervosa. Adult aphids are about 1 mm long. Photo: J. Thomas, UQ.

By selecting “hot spot” areas in the plantation and carefully inspecting all plants in the area individually, stem by stem, we have shown that the inspectors’ high rate of positive identifications (>80%) is being maintained here. However, using laboratory tests on leaf samples from these plants, we found that BBTV was detectable in some recently infected plants before they showed symptoms. In other plants, the virus was detected in the symptomless leaf formed immediately prior to the first leaf to show symptoms.

This should not be a concern for disease spread if the virus was not transmitted from these symptomless, but infected, leaves. However, to our surprise, when we fed aphids on these leaves, the virus was transmitted to healthy banana plants. Furthermore, the rate of virus transmission was similar regardless of whether the aphids fed on infected leaves with symptoms or without symptoms.

The map shows a survey area where symptomatic (red) and pre-symptomatic (yellow) plants were located amongst the healthy (green) plants. We found that the virus was transmitted from thirteen symptomless leaves, eight of which remained symptomless over the whole three-week observation period.

Our next step is to determine whether these infectious, asymptomatic leaves are produced by BBTV-infected plants year-round or in a seasonally dependent pattern.

This plantation was poorly managed, with limited de-leafing, providing a sheltered environment for the banana aphids to multiply. De-suckering was also limited, thus providing more susceptible young plants (favoured by the aphid) that are often obscured by the dead leaf skirts. We suspect that the higher aphid numbers along with the higher number than expected of infection sources present as symptomless, infected leaves and obscured, infected suckers, combine to promote and prolong the epidemic.

Map of plants assessed in this study.
Checking the youngest leaf of each stem for symptoms. L-R: Dr Nga Tran, A/Pro John Thomas, Dr Mona Moradi Vajargah. Photo: K. Crew, DAF.
The laboratory testing team subsampling field samples. L-R: Dr Kathy Crew, Dr Nga Tran, A/Prof John Thomas, Dr Mona Moradi Vajargah, Dr Megan Vance. Photo: D. Baker.

Remember

•   BBTV-infected plants can be infectious prior to development of leaves with symptoms.
•   Removing newly infected plants promptly slows the spread of the virus.
•   Four-week inspection cycles during the summer months in high disease pressure situations can reduce but may not         completely suppress the outbreak.
•   Any reductions in inspection frequency will allow the epidemic to take off.
•   Plantations need to be well-maintained to limit aphid vector numbers.
•   Grower participation in detection and eradication between formal inspections is likely to have a significant beneficial 
     impact on control.     

More information

This research has been funded as part of the Improved Plant Protection for the Banana Industry Program (BA19002), 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. 
Support for the establishment of research sites and identification of infected plants has also been provided through Hort Innovation Project BA21003 “Multi-pest surveillance and grower education to manage banana pests and diseases”.

 

 

Banana bunchy top disease

Posted on by Better Bananas

Banana bunchy top disease

Banana bunchy top is considered the most serious viral disease of bananas worldwide

Banana bunchy top disease (BBTD) reduces the growth of banana plants and causes bunching of newly emerged leaves (Figure 1). Infected plants rarely produce fruit and are a source of inoculum for further spread, which can lead to serious commercial losses if not promptly eradicated. The disease is caused by a virus (banana bunchy top virus, BBTV) and affects all banana varieties. Unfortunately, there is no cure for the disease, once a plant becomes infected it must be destroyed as all parts of the clump/stool/mat are also infected. 

Figure 1 Banana plant infected with BBTV. Image shortening and bunching up of new leaves with yellow margins (photo courtesy of Australian Banana Growers Council)

BBTV is spread two ways, by banana aphids and infected plant material

BBTV is transmitted by a small black insect (1.5–2.0 mm long) called the banana aphid Pentalonia nigronervosa (Figure 2 & 3). Aphids that feed on infected plants can carry the virus spreading it to healthy plants as they feed. Aphids can carry the virus for several weeks and may cover large distances when blown by the wind. The virus can also be spread to new areas from infected planting material. It’s important to note that plants can be infected with the virus without showing symptoms. It’s always recommended that you source tissue cultured planting material from a Quality Approved Banana Nursery (QBAN) to minimise the risk of introducing serious pests and diseases onto your farm, such as Panama disease, BBTV, banana weevil borer and many more. Click here for a list of QBAN accredited nurseries. 

New research discovers new findings on virus transmission and explains why this disease is so hard to eradicate.
Click here for more information. 

Figure 2 The banana aphid, Pentalonia nigronervosa. Adult aphids are about 1 mm long. Photo: J. Thomas, UQ.
Figure 3 Banana aphids on banana leaf petioles.
Figure 4 Ants and aphids living and feeding together. Image also shows numerous white cast skins of banana aphid (photo courtesy of Australian Banana Growers Council)

Control and containment activities continue to play an important role in limiting the spread of BBTV within Australia.

Banana bunchy top disease was first discovered in Australia over a century ago in the Tweed River region, located on the New South Wales and Queensland border. To date the disease has been successfully contained within the Bunchy top zone of South East Queensland and northern New South Wales. The banana growing regions of Far North Queensland, Northern Territory and Carnarvon in Western Australia remain free of the virus. However, it’s important for banana growers across all production regions to be on the lookout for BBTD symptoms. 

What to look out for?

Early symptoms of BBTD can be difficult to detect to the untrained eye. If you have stunted or unthrifty banana plants, examine the leaf lamina of the newest banana leaves for short dark green on lighter green dot-dash lines starting from, and sometimes extending or ‘hooking’ into, the mid-rib (Refer to photos below). You can see them best if you hold the leaf up to the light and look through from the underside of the leaf. There may also be dark green stripes running along the mid-rib. Plants with advanced infection have stunted looking leaves and a bunched appearance (bunchy top). If bunches are present, they may be small and deformed. 

Do not cut or disturb plants or move plant material off your property as this can spread the disease. 

Key symptoms

  • Dark green on lighter green, dot-dash flecks (sometimes called Morse code streaking/patterning) on leaves.
  • Dot-dash flecks are initially visible along the lower edge of the leaf’s midrib, then progress to the leaf veins adjacent to the midrib, and gradually becoming more prominent across the leaf blade. 
  • Eventually dot-dash flecks can form into irregular streaking. 
  • Leaf flecks and streaking are most visible when viewed from the underside of leaves.
  • Flecks in veins can form a characteristic ‘hook’ shape at the point where the midrib meets the leaf blade.
  • Vein-flecking can also be seen on the petioles and in the leaf sheaths of stems.
  • Growth of the whole plant is reduced and emerging leaves develop a choked or ‘bunched” appearance.
  • Affected leaves often appear more upright with pale yellow margins, and may have wavier leaf edges than normal.
 
Image of advanced BBTV symptoms in a banana plant. Shortening and bunching up of new leaves with yellow margins (photo courtesy of Australian Banana Growers Council)
Image of advanced BBTV symptoms in a banana plant. Stunted growth and emerging leaves develop a choked or ‘bunched’ appearance
Dark unbroken stripes along the leaf midrib (not always present) (photos courtesy of Australian Banana Growers Council)
Dark unbroken stripes along the leaf midrib (not always present) (photos courtesy of Australian Banana Growers Council)
Dark green on lighter green, dot-dash flecks (sometimes called Morse code streaking/patterning) on leaves (photo courtesy of Australian Banana Growers Council)
Do your staff keep an eye out for Banana bunchy top?
Do your staff keep an eye out for Banana bunchy top?

ABGC have produced the following video on how to detect Banana Bunchy Top Virus symptoms in commercial plantations. 

How to report

It’s important for banana growers across all production regions to be on the lookout for BBTD symptoms.
Growers or members of the public that suspect BBTD must immediately notify their state’s biosecurity agency or through the bunchy top hotline 1800 068 371. Early detection and destruction are critical to limit its spread. Strict quarantine restrictions remain in place to prevent the movement of contaminated planting material.

Surveillance and containment work within the known bunchy top zone is continuing as part of Hort Innovation’s ‘Multi-pest surveillance and grower education to manage banana pests and diseases’ project, led by the ABGC. This important work is aimed at controlling and containing the disease within the known BBTV zone, supporting the commercial industry within this zone and aims to prevent its spread to other commercial growing regions within Australia. Click here to read more information about this project.

Currently, there is no cure for BBTV and there are no known resistant banana varieties. Control is only achieved through the destruction of infested plants and banana aphids. Early detection and destruction are critical to limit the spread of BBTD.

Latest research update

Click here to read about the latest new research that helps explain why banana bunchy top disease is hard to eradicate.

More information

In collaboration with ABGC, this information has been compiled by the National Banana Development and Extension Program (BA19004). This project has been 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.

Getting the best from your tissue culture

Posted on by Better Bananas

Recent trial work has found that undertaking an additional early desuckering application in the plant crop of tissue-cultured plants can significantly improve yield and stability in the following ratoon crop.

A different approach to desuckering tissue cultured plants

Desuckering is one of the most important management requirements in a banana plantation. When using Cavendish cv. Williams tissue culture, a different approach to sucker management needs to be adopted as opposed to managing suckers from conventional planting material such as bits. 

The corm from the mother plant grown from tissue culture is generally ‘V-shaped’, rather than a ‘U-shaped’ corm, typical of bits and suckers (Figure 1). A ‘V-shaped’ corm means that sucker development of tissue culture plants comes from underneath the corm in a spiral sequence upwards (Figure 1). 

The connection of these early suckers (referred to as ‘first flush’ suckers) to the mother plant are small and weak (Figure 2). A small and weak connection from the mother to the follower can restrict flow of nutrients, leading to the follower having reduced growth, poor vigour, and snapping away from the mother plant. 

Figure 1 Sucker development from bits or suckers is generally a ‘U’ shape originating higher up the corm. Suckers derived from tissue culture develop from underneath the mother plant and lower down the corm.

What is a flush of suckers?

The first series of suckers that emerge all at once are known as the first flush. These suckers are early suckers and are set low down on the corm.

Figure 2 First flush suckers from tissue culture plants have a small and weak connection to the mother plant. Whereas second and third flush suckers have stronger connections.

About the trial

A trial conducted at South Johnstone Research Facility investigated whether plant agronomic characteristics significantly improved by undertaking an additional early desuckering application in the plant crop. The trial also looked at the physical connection between the sucker and mother plant. 

Comparing agronomic performance

The trial consisting of 330 Williams Cavendish tissue culture plants had two desuckering treatments applied.

1. Desuckering twice (early & late) – Fifty percent of plants were desuckered twice, once at 3 months after planting, where all of the first flush suckers were removed (via cut and kerosene). The second desuckering treatment was at the commencement of bunch emergence, when sucker selection for the first ratoon crop was conducted.

2. Desuckering once (late only) – The remaining 50% of plants were only desuckered once, at the commencement of bunch emergence. This is when sucker selection for the first ratoon was undertaken.

Comparing sucker connection

A small number of plants not included in the agronomic assessments were used to inspect the physical connection between the suckers and mother plant. Half of the plants received no desuckering (Figure 3) and the other half received an early desuckering where the first flush of suckers were removed at three months after planting (Figure 4).

At the commencement of bunch emergence, plants were dug up to determine if there was a visual difference in the connection to the mother plant and whether sucker development improves with early desuckering.     

Figure 3 Left: Plant not desuckered. Right: The same plant dug up at commencement of bunch emergence with the soil and roots removed. Visual observations showed first, second and third flush sucker development, with smaller and weaker connections compared to the plant that received the early desuckeringtreatment below (Figure 4).
Figure 4 Left: Plant desuckered early (First flush suckers removed 3 months after planting). Right: The same plant dug up at the commencement of bunch emergence with the soil and roots removed. Visual observations showed fewer suckers with stronger and larger connections compared to the plant that received no desuckering treatment above (Figure 3).

Results

  • Plants desuckered once (late only) produced significantly shorter plants in both the plant and first ratoon crop (Table 1).

  • Plants desuckered twice (early & late) produced significantly heavier bunches in the plant and first ratoon crop compared to plants desuckered once (Table 1).

Table 1 Effect of desuckering treatments on plant agronomics in the plant and first ratoon crop
Average plant height and bunch weight for plant and ratoon crop cycles

  • The largest difference in bunch weight was in the first ratoon crop. Bunches were 26.9% heavier in plants that were desuckered twice than plants desuckered once. The heavier bunch weight was a result of a higher number of hands per bunch, finger length and average fingers per bunch.

  • First flush suckers have smaller and weaker connections, approximately the size of a 10 cent piece. Second and third flush suckers have larger and stronger connections (Figure 5), making ratoon plants less vulnerable to uprooting and snapping.

  • Undertaking the first desuckering at or close to the commencement of bunching can result in:
     – Poor sucker selection, due to difficulty in determining first, second or third flush suckers.
     – Increased risk of uprooting, due to removal of unwanted suckers all at once, destabilising the plant.

Figure 5 Size of sucker connections to mother plant

Take home messages

  • Removing suckers early improves yield and plant stability of ratoon crops.

  • Tissue culture produced under the Quality Banana Approved Nursery Scheme (QBAN) is recommended best practice when establishing a new farm or replanting old blocks. QBAN tissue culture ensures that pests and diseases are not introduced and/or spread within and between farms.

Download this information as a fact sheet

More information

Click on the video below to watch a field day presentation on this work, presented by  Research Horticulturist Shanara Veivers.

This research has been funded as part of the National Banana Development and Extension Program (BA19004), 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.

Postharvest

Posted on by Better Bananas

Postharvest research and development

Postharvest research plays an important part in guaranteeing that Australian’s keep enjoying great quality bananas. A lot of time and effort goes into producing each and every bunch. Therefore, having correct postharvest processes in place for handling, storing and ripening fruit is essential to get the best quality fruit onto retail shelves and to maximise the fruit’s value back to growers.

Research looking into postharvest processes on-farm, as well as within the supply chain, has gone a long way in understanding and addressing some important quality issues. The links below provide more information on recent postharvest research.

If you have a postharvest issue that you would like to discuss or would like further information, contact the Better Bananas team at betterbananas@daf.qld.gov.au.

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