November 2013 The Plant Industries NT eNewsletter Welcome to another issue of the PINT newsletter. Not surprisingly, mangoes are the flavour of the season and of this newsletter. Two articles are presented, the first around the second year’s trial results investigating the impact of foliar calcium sprays for reducing lenticel damage. This effort essentially confirms last year’s work – thus we can now consider the results as real, and not an anomaly. The second article focuses on the highly publicised issue of resin canal disorder. This topic became a media sensation when it was reported that Northern Territory mangoes were being downgraded in southern markets by a mystery disorder. The segment will discuss some background with the disorder, the aims of the research project into the problem, and interim findings and observations. What is certain is that there remain a number of unknowns about resin canal. The project will attempt to provide some advice on the priorities for further investigation. Mango tip-borer is on the rampage in some local Darwin mango orchards. Find out why it is so important to manage their populations – next year’s income could depend on it. Finally, an update on Banana freckle and steps being undertaken to eradicate the disease. 1 The PINT Newsletter is produced by the Plant Industries Division of Department of Primary Industries and Fisheries. For further information please contact: Warren Hunt, Extension Leader (08) 8999 2143 or 0409 809 610.
Transcript
The Plant Industries NT eNewsletterNovember 2013
Welcome to another issue of the PINT newsletter. Not surprisingly, mangoes are the flavour of the season and of this newsletter.
Two articles are presented, the first around the second year’s trial results investigating the impact of foliar calcium sprays for reducing lenticel damage. This effort essentially confirms last year’s work – thus we can now consider the results as real, and not an anomaly.
The second article focuses on the highly publicised issue of resin canal disorder. This topic became a media sensation when it was reported that Northern Territory mangoes were being downgraded in southern markets by a mystery disorder. The segment will discuss some background with the disorder, the aims of the research project into the problem, and interim findings and observations. What is certain is that there remain a number of unknowns about resin canal. The project will attempt to provide some advice on the priorities for further investigation.
Mango tip-borer is on the rampage in some local Darwin mango orchards. Find out why it is so important to manage their populations – next year’s income could depend on it.
Finally, an update on Banana freckle and steps being undertaken to eradicate the disease.
Readers are encouraged to explore the Useful Links and Upcoming Events
sections. There are two valuable workshops being run in early December around effective mango orchard nutrition. The guest present/expert is Ted Winston from Tropical Horticultural Consulting in Queensland. Ted will be conducting comprehensive training starting with the basics and working through a thorough program designed to assist growers and agri-business advisors to better understand the key strategies for healthy and productive orchards that can deliver quality fruit.
Regards,
Warren Hunt
In this edition:
Update: Year 2 Jabiru Orchard trial on foliar calcium for reducing incidence of lenticel spotting...................................................................2
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The PINT Newsletter is produced by the Plant Industries Division of Department of Primary Industries and Fisheries. For further information please contact: Warren Hunt, Extension Leader (08) 8999 2143 or 0409 809 610.
Progress on the investigation into resin canal disorder in mangoes 3Set up next year’s crop: Preventing Large mango tip-borer from destroying your post-harvest flush...........................................................5Banana Freckle: behind the scenes..........6
Update: Year 2Jabiru Orchard trial on foliar calcium for reducing incidence of lenticel spotting By: Chris Kelly, Chelsea Moore, Cameron McConchie and Warren Hunt NTDPI&F
The problem
Lenticel spots are the most common downgrading defect in the NT.
Studies have shown nearly a quarter (22%) of NT fruit can be downgraded because of lenticel damage.
Pre-harvest moisture and post-harvest exposure to water are known causes.
Stress through chilling injury can also cause some lenticel damage as can secondary infections through ruptured cells.
The role of calcium in fruit
• Tree transports calcium into the fruit in small amounts.
• Calcium tends to be transported into fruit early in development, peaking & then declining during the cell expansion stage.
• Calcium stabilises cell membranes - deficits cause a deterioration of cell membranes, loss of turgor & leakage of cell fluids.
• In apples lenticel breakdown is complex - includes interrelationships between soil, fertilisation, irrigation, rootstock, fruit/leaf ratio, vigour, & weather.
Method
• Three treatments were undertaken: 1) Control (water).2) VigorCal™3) Biomin™
• Applied via a multi-fan sprayer.• Six replications of each. • Twenty fruit per replication were
harvested and assessed.• Samples were taken from four trees in
each replication.• Two guard trees were positioned within
rows and four between rows.• The trial was sprayed weekly for five
weeks from nubbins size onwards.
Figure 1. Trial layout
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Results for impact on Lenticels:
Table 1. Means of lenticel scores across treatments
Rep. Water VigorCal Biomin Mean
1 1.27 1.57 2.14 1.66
2 1.71 2 1.61 1.77
3 2.3 1.88 1.84 2.01
4 2.12 2.57 1.88 2.19
5 1.67 2.18 2.1 1.98
6 1.37 1.56 1.86 1.60
Mean 1.74 1.96 1.905
This trial determined that no discernible advantage could be gained against lenticels from applying foliar calcium from either of the treatments used. This is consistent with the trial results from 2012.
Conclusion
The message is that if you are applying foliar calcium to minimise lenticel defects then the biggest effect it will be having is impacting your bank account.
Progress on the investigation into resin canal disorder in mangoesBy: Peter Hoffman, Andrew MacNish, Darryl Joyce, Terrence Campbell (DAFFQ); and, Cameron McConchie, and Chelsea Moore NT DPI&F.
Resin canal emerged as a major issue in many parts of the Northern Territory and Queensland in 2012-13 season. The Australian Mango Industry Association (AMIA), and the NT and Queensland Governments recognising this as a potentially serious issue invested in a research program in early 2013 to begin to better understand the distribution, frequency and causes of the disorder. Since the beginning of the 2013 harvest season there
has been intense local interest in the NT subsequent to a major packing business reporting serious losses from the disorder.
While the occurrence of resin canal can be financially problematic for a shipment of fruit, quantitative measures of the extent and magnitude of the defect is lacking. This is in part due to an absence of a consistent means of measuring its occurrence. A good deal of the current research has been aimed in these areas.
Background
Mangoes have a system of ducts (or canals) running through the fruit and stem. These are likely to function as part of the defence system of the plant. In mature fruit these canals run through the flesh, forming a network of channels. Sap (or resin) is maintained under pressure in these ducts. On picking, or injury to the skin, resin is exuded from the ruptured canals. Resin canal is a disorder that becomes apparent during ripening. It is not visible at harvest. The aesthetic effects of the condition render affected fruit unsalable. As shown in the images in Figure 1, resin canal appears as a browning of the cells in a cluster of discrete spots. The spots are initially light but as the condition progresses they become darker, sometimes complete coverage can occur before the fruit reaches a ripe yellow colour.
Figure 1. External appearance
Internally it is characterised by red or brown streaks (Figures 2 & 3) that run from the
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skin into the flesh along the fruit’s resin canals – hence the name. In October 1995 a market survey of NT supplied mangoes showed that as much as 32% of fruit were affected with resin canal (Landrigan 1995). A more extensive study conducted in 2011 by the Australian Centre International Agricultural Research (ACIAR), found resin canal at lower levels (3%).
Figure 2. Streaks of ruptured resin canals in fruit
Figure 3. Close-up cross sectional view of a ruptured resin canal
Although this disorder has been documented in the Northern Territory for many years, it has largely remained unimportant until the 2012-13 season when market agents reported high numbers of fruit with the defect. Resin canal has traditionally not been a documented problem in Queensland fruit (with the exception of recorded incidences in the
Burdekin). In the NT, incidence appears to be higher for some growers than others. It is found in both Darwin and Katherine fruit, and almost exclusively on Kensington Pride, although some past reports have listed it on certain Asian varieties as well.
Interim findings from the 2013 research
Resin canal disorder increases in severity as fruit develop from firm ripe to overripe; hence surveys at the wholesalers may under-estimate the impact of resin canal, because fruit on the retail shelf will be riper and likely to show more symptoms.
Resin canal has also been found in orchards in hard green mangoes. The disorder can occur in all stages of maturity from less than 12% dry matter to greater than 15%. This is usually associated with damage by birds, insects or from other forms of skin damage. This is evident at early-stages as red flecking in the skin which later darkens. This usually covers the entire fruit surface though it can be patchy. Fruit with this form of the disorder soften normally during ripening but do not de-green. The resin canals affected lie under the skin, along the under-surface and across the surface of the seed and extend into the fruit stalk. It does not seem to extend beyond the abscission layer in the fruit stalk (i.e. the point where the stalk would commonly separate when harvested). This form of resin canal can easily be detected on a well-lit packing line and occurs at a low frequency (<1%).
In very ripe fruit when the slightest level of infection by stem end rot or anthracnose occurs, discoloured resin canals radiate through the flesh. These susceptible types of obviously non-commercial fruit can see very high incidences of resin canal (>60%).
The financially more serious form of resin canal shows no visual symptoms going across the packing line. It appears during fruit ripening and may be evident as black
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flecks on the skin surface that lead to the web of resin canals in the fruit flesh and over the seed. Note: some fruit exhibit no external signs of the defect even at ripening. The discoloured resin canals in the flesh can only be detected by cutting the fruit. This means that inspection after ripening without cutting does not give an accurate estimate of the level of defect, and consumers can purchase fruit with defects even after standard sorting practice in the packing shed or by the wholesaler or retailer. While this form of the disorder often only affects 2-3% of fruit in shipments, it can unpredictably occur in over 50% of fruit in other shipments. There seems to be considerable variation between farms and between shipments from the same farm.
Except in extreme cases - the fruit taste the same as fruit without the defect.
The incidence of resin canal disorder is relatively higher in fruit that are exposed to typical commercial harvest, pack-house and distribution procedures than those ripened directly off the tree.
The results from the current season’s investigations on the effects of rain, fruit maturity, transport and chemical are still being compiled. At this early stage there did appear to be a higher level of the disorder in trial consignments assessed after arriving in the market, compared to fruit left to ripen at 22°C in Darwin.
Going forward – there remains a need to develop accurate measures of the defect to be able to separate seasonal, regional and shipment effects, and show that it can be effectively controlled. Researchers want to develop an assay (process) to induce the disorder so that susceptibility can be demonstrated in a short period without the need to ship fruit through the supply chain. This will also assist the development of methods to manage the defect in susceptible fruit.
We thank Horticulture Australia Ltd, the Australian Mango Industry Association, and Tim Elliott of W.E. Pack Pty Ltd for financial support. We acknowledge the technical assistance and advice of colleagues in QDAFF, UQ and the NT DPI&F.
Set up next year’s crop: Preventing Large mango tip-borer from destroying your post-harvest flushBy: Cameron McConchie and Brian Thistleton NT DPI&F
Penicillaria jocosatrix (Large Mango Tip-Borer) is a pest that deserves grower’s attention immediately post-harvest as the plant begins to flush. Kensington Pride mango trees essentially shut down their photosynthesis in the dry, therefore the time in which to build up the trees’ reserves is now when it is actively growing. Rampant attack from mango tip borer caterpillars erodes the plant’s photosynthetic capacity (kills off the new flush) and thereby its ability to store away carbohydrates - which is effectively your next season’s crop. Also with new leaf recruitment compromised, the plant is further affected when the older leaves fall, leaving it less collective photosynthetic ability.
Larvae (the caterpillar Figure 1) feed mainly at night on the new flush before it changes from purple to green. Immature larvae feed on the leaf surface around the edges, which produces a window-like effect. As larvae mature the entire leaf may be eaten, giving them a ragged edge or skeletonised.
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Both surfaces of the new flush and mature leaves should be inspected for eggs and larvae in the evening when caterpillars are more active. Look for fresh caterpillar droppings or frass on new flush growth.
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Figure 1 Large Mango tip-borer caterpillers
The knockdown insecticides Success Neo™ (active ingredient – spinetoram 120g/L), and carbaryl, are registered for use against Large Mango Tip-Borer caterpillars. Bacillus thuringiensis (use only on small caterpillars less than 8 mm) can also be used.
Banana Freckle: behind the scenesBy: Darrel Trueman NT DPI&F
I’m wearing a bright green reflective vest with the words Communications Manager emblazoned on the front and back as I enter the house-sized Biosecurity and Product Integrity Group building. Inside it’s a hive of activity.
Several people work at desks and tables in an open office, its white walls covered in maps, charts, and schedules. To one side, a man wears a vest similar to mine, though it’s red, and reads Investigations Manager. Smaller rooms throughout the building are labelled Controller, Biosert, and Teleconference in Progress. Notes are
jotted on whiteboards. Landlines and mobiles ring. Photocopiers whirr.
A woman wearing a bright blue vest that reads Logistics Manager is focussed on a computer screen, her fingers flying across the keyboard as I approach. She glances up briefly. “I’m going to ignore you because I’ve got lots to do,” she says with a laugh and a smile. I smile back.
There is indeed lots to do. Welcome to the local control centre for banana freckle eradication, at the NT Department of Primary Industry and Fisheries (DPIF) campus at Berrimah Farm on Darwin’s southern outskirts.
Figure 1. The Control Centre
Since the attractively-named Phyllosticta cavendishii was discovered on Cavendish bananas in the NT in August, DPIF staff from across the NT, biosecurity experts from interstate, and contractors have worked on the eradication full time—including evenings and weekends—seven days a week. So far they’ve identified 15 infected properties, destroyed bananas on almost 300 properties, and conducted surveillance on over 3000 properties.
P. cavendishii is a major concern because whilst it has been in the NT for 20 years, it has previously only been found on Lady Finger and other non-Cavendish varieties; but this is the first time it’s been confirmed on Cavendish, the main commercial variety. If the disease spreads beyond the Territory,
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it could have a significant negative impact on Australia’s $450 million banana industry.
Over in the control centre’s DDD area—that’s destruction, disposal, and decontamination—a DPIF staff member seconded from the business development area has brought her people and organisation skills to the team. On the wall beside her computer is an impressively-detailed, colour-coded flow chart she’s created to clearly identify the many steps in the eradication processes.
Figure 2. DDD heavy machinery in action
“I phone residents to give them the bad news—that we’re coming to chop down their banana plants,” she says. “I have a background in dealing with difficult people. It’s not always easy, and some people might not react very well to the news, so I do my best to treat them with courtesy and consideration.”
In another wing of the building, the Banana Freckle Hotline is ringing. “We received over 275 calls in November,” says an operator who enters details into a computer. “I open a new file for each new caller, 40% of whom don’t have bananas, but they’re ringing us anyway, often because we’ve left a surveillance note on their gate.
“A small number of people don’t want us to enter their property, but most accept that we have an important job to do.” She points to notes on the screen. “This gentleman was rather chatty, telling me about the fabulous
holiday he’d just had in the Philippines”. I read the comments next to his contact info: ‘Works away from home; can inspect when no one is home; just jump through the hole in the fence’.
Planning Manager, screams the bright yellow vest worn by a friendly but no-nonsense biosecurity expert who’s recently arrived from Tasmania to assist our team. “This work is highly structured,” she says. “Part of my job is to ensure that there’s no loss of accountability, all roles are clear, and nothing is overlooked. We also keep tight reins on where the money is being spent, and what it’s being spent on. Having a good outcome is our focus”.
I peer out a window of the air conditioned control centre. It’s hot and sticky out there today, 33˚ with 64% humidity. I think about the rest of our team, the dozens of surveillance and eradication staff and contractors. They’re fanned out across the Darwin and rural area, talking to residents, checking properties, swinging machetes, hauling heavy banana trees through the heat. It’s hard yakka, and I’m grateful they’re on the front lines, helping us to control this pest that threatens the livelihoods of so many people.
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Useful LinksAPVMAPublic Chemical Registration System http://services.apvma.gov.au/
