Mango Management _DBIRD_NT_ by decree

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									Agnote
                                                                           301
                                                                           No. D9

                                                                           December 1999

                                                                           Agdex No: 234/11

                                                                           ISSN No: 0157-8243




Mango Management –
Flowering to Market
M. Poffley, G. Owens and V. Kulkarni, Horticulture Division, E.S.C. Smith and B. Condé, Resource
Protection Division, Darwin




Top quality mangoes are no accident - Good orchard management is the first step.

As in the case of any other crop, profitability of mango growing depends on high yield of top
quality fruit. To achieve this goal, there should be profuse, early-flowering, high fruit-set and
retention, proper management of pests and diseases, adequate supply of nutrition, proper
assessment of fruit maturity and proper post harvest handling of fruit.

The management cycle of mango can be
divided into two major sets:

1. Flowering to market.
2. Harvest to subsequent flowering.

It is important to realise that both of these
have a profound impact on productivity
and profitability.

This publication deals with management
from flowering to market, which involves
managing the trees and orchard floor from flowering to harvest, and harvesting and handling the
fruit until it is sent to market.

FLOWERING TO HARVEST

Major issues from flowering to harvest are pollination and fruit-set, nutrition, irrigation, pest
management, assessment of fruit maturity, harvesting and prevention of sap burn.

Pollination and fruit-set:
Flowering time for the Kensington Pride mango in the Top End extends from May to August and
harvest time from September to November. The mango is insect pollinated. Steps taken to
improve and sustain the activity of insect pollinators is of immense value. Flies and bees are the
main pollinators. It will therefore be beneficial to increase their numbers. Beehives can be
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installed at flowering time. The population of flies can be built by initially rearing them in
containers of pet meat and releasing them in the orchard. Alternatively, native bees are also
very important in pollination.

Pesticide sprays should be avoided during peak pollination and fruit set time, as they will be
hazardous for the pollinators. Such sprays should be timed to avoid the time of major fruit-set.

Irrigation:
It should be withheld until 60% of flower buds are visible. As a rough guide to the amount and
timing of irrigation each tree should receive 80 litres of water per week, per year of age, in three
applications.

Using this method the maximum amount of water applied is in year 10 i.e. (2,400 L/week per
tree).

Reducing irrigation to 300-400 L/week (for a 10-year-old tree), three to four weeks prior to
anticipated harvest, increases dry matter levels. If water is cut off completely, it could have side
effects such as smaller fruit and risk lower quality fruit by inducing jelly seed and stem end
cavity.

For more detailed information read Agnote No. D14 "Mango Irrigation Guidelines".

Nutrition:
The nutrient levels in the soil and leaves should be tested prior to flowering when the trees are
in the dormant phase. This will allow specific applications of required fertilisers to bring the
levels up to optimum for each nutrient. (See Agnote No. D41 “Mango Leaf and Soil Analysis”
and No. D39 “Mango Leaf and Soil Sampling”). This will provide the best chance for a
satisfactory crop to set and develop. There are a number of commercial soil sampling services
available to growers through fertiliser distributors and retailers.

Without these tests, only a general recommendation may be made to supply the major nutrients
that will be needed in this period. These recommendations are a guide only.

Gypsum should be applied at 100-200 g/m2 uniformly under the canopy and before irrigation has
commenced. Calcium sprays in the chelated form can also be used as directed on the label.

Solubor should be applied at the same time as a soil drench over the gypsum with a 0.5–1.0 g/L
solution and at a rate of 5 g for small trees, 10 g for medium and 20 g for large trees.

Muriate of Potash at 30 g/m2 should be applied when irrigation is commenced at 60% flowering.

Superphosphate with trace elements at 60 g/m2 should also be applied when irrigation begins.

Trace element sprays should have been applied during the late flush of the Wet season and
should not be applied to flowers or developing fruit.

Leaf and soil tests should be done every year before flowering and after harvest to establish the
correct balance of nutrients.

Using potassium nitrate as a foliar spray to initiate bud burst is not a true nutrient application.
Some growers have used potassium from about mid-May to promote bud burst and panicle
development. However if applied too early or during hot weather it can result in vegetative
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flushing rather than flowering. Growers intending to try this technique are advised to seek more
information before attempting it.

After harvest, apply a complete fertiliser, with a formula of approximately 12N - 12P - 12K at the
rate of 20-30 g/m2.

Trace element sprays should be applied pre flowering, as foliar sprays. Sprays on developing
fruit can cause problems such as lenticel spotting.

Applying sprays

If possible avoid spraying during flowering. Check for and treat any problems before flowering.
Keep post flowering sprays to a minimum to reduce the possibility of skin damage to the
developing fruit. It is however important to remember that damage done to fruit at an early stage
can lead to severe scarring and disfiguring in fully developed fruit, making it unsuitable for the
fresh market.

Dilution rates vary with brands. Compatibility of chemicals also varies. Follow directions
carefully.

PESTS

Good management includes regular orchard inspection to monitor pest and disease
levels.

Flower eating caterpillars can significantly reduce potential yield if a severe infestation occurs.
Symptoms are flower buds being eaten before they have fully opened or webbing in the panicle
with all the flowers stuck together in a loose clump. Control can be achieved by using a
bacterium, which only attacks the caterpillars and not the pollinators, i.e. Bacillus thuringiensis.
This is available under a number of trade names such as DiPel® and MVP. This should be used
as per label, as different brands have different rates. The other method is to use a short residual
life chemical. e.g. Trichlorfon 625 g/L (Dipterex®, Lepidex®). This should be sprayed in the late
evening when most pollinators are not active. Usually one spray is sufficient to give effective
control.

Red-banded thrips should be controlled before flowering but are active at this time of year and
can attack flowers or developing fruit at any time, resulting in brown scarring on the fruit.
Symptoms on leaves include a dead area along the mid rib; in severe cases whole bunches of
leaves dry off and die. Thrips are usually found on the under-side of leaves. Adults are 1-2 mm
long and black in colour; nymphs are smaller and translucent with a red band across the middle.
If they are still active, close inspection will reveal small shiny, black spots, like tar (pinhead size
and smaller) which are their faecal deposits. A spray with one of the following insecticides, plus
a wetting agent will control them:

•   Dimethoate (Rogor®, Diostop®)
•   Trichlorfon (Dipterex®, Lepidex®)

A follow-up spray 10 to 14 days later may be necessary if inspection shows any signs of
reinfestation. For more information, see Agnote No. I44 “Redbanded Thrips on Fruit Trees”.
                                                 4

The mango leafhopper is a new pest to the Top End and is widespread in the older suburbs of
Darwin but as yet, very restricted in the rural area. Populations of the small (4-5 mm) gold brown
wedge-shaped leaf hopper build up very rapidly during flowering and release copious quantities
of honey-dew, leading to sooty mould on leaves and inflorescences. Heavy infestations will
wither flowers and cause significant yield loss. Control is effected with two sprays of trichlorfen,
7-10 days apart. Agnote No. I48 “Mango Leafhopper” gives further information on damage and
control.

Flatids are found on most mango trees in the Top End. Adults are green or whitish-green in
colour, 10-15 mm in length and triangular shaped. The immature stages are covered in whitish
wax and move rapidly when disturbed. They are often found lined up along the stalks of
developing fruits where they feed by sucking sap. Sooty mould is associated with high numbers
of these pests. If numbers are high during flowering, it is best to wait until flowering finishes
before applying carbaryl at 10-day intervals. Numbers will be held in check if cover sprays as
part of the ICA agreements are used.

Scale insects and Mealy bugs are flat round insects, about 2-3 mm in diameter and can be
found on leaves, stems and fruit. Sucking sap from the plant results in heavy damage. Heavy
infestations result in die back and bark splitting.

Mango scale (Phenacaspis dilatata) is the most common and appears as white flecks usually
found under older leaves. The leaves where they have been feeding develop yellow spots, often
the centre dies, resulting in a black angular centre spot surrounded by a yellow halo. These are
common on older trees and usually do not warrant any control in the Top End, as the damage
they do is minimal.

Pink wax scale (Ceroplastes rubens) are larger, 5-8 mm and hemispherical in shape. They
appear in clusters of pink blobs along the midribs on the upper surface of older leaves. They are
invariably associated with sooty mould, which as the name implies gives surrounding leaves a
black sooty appearance. Infestations are an indication that the natural enemies have been
destroyed by inappropriate pesticide applications.

Mealy bugs have a white fluffy appearance. They usually congregate along the under side of
leaves and along twigs near the growing tips; they can also be found in inflorescences. They
are soft and, when crushed, leave an orange coloured residue. They are sometimes associated
with sooty mould when large numbers occur on the tree.

Trees with pink wax scale and mealy bug infestations will usually have large numbers of ants
active on them. The ants "farm" and protect them in exchange for a "honey-dew" secreted by
these insects.

Usually two applications, at 7 to 10 day intervals, using any of the chemicals listed below, will
control these insects. All these chemicals should be mixed with petroleum oil (e.g. DC TRON®
oil at 10 mL/L).

Carbaryl (various formulations)
Dimethoate (Rogor®)

Fruit flies attack maturing and sometimes green fruit. The variety Irwin is particularly
susceptible to fruit fly even when the fruit is quite young.
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Interstate Certification Assurance (ICA-19) is required for mangoes from Queensland fruit fly
affected areas in the Top End, as a condition of entry to interstate markets. All affected growers
intending to export mangoes interstate, other than to Sydney or Brisbane must be registered
with AQIS.

The ICA –19 requirements have changed as the NT has successfully eradicated the exotic fruit
fly. For the 1999-2000 season pre-harvest cover sprays of dimethoate and fenthion or bait
sprays are not required for Kensington Pride (KP) mangoes.

KP mangoes will still meet ICA-19 standards for Melbourne or Adelaide without pre-harvest
cover or bait sprays.

All other varieties DO require pre-harvest treatments of either bait sprays or cover sprays.

Pre harvest fruit fly treatment is however good management as any infested consignment found
anywhere will be seized and destroyed. It is therefore recommended that all mangoes be
treated either with cover or bait sprays described below and records kept.

1. Cover spray: Full orchard spray with 75 mL/100 L water, of either 550 g/L formulation of
   fenthion or 400 g/L formulation of dimethoate.

2. Bait spray: Applied at 100 mL/tree or 10 L/ha on at least every second tree. The bait is
   prepared with 435 mL of maldison concentrate of 1,150 g/L maldison solution and 2 L of
   protein autolysate in 100 L of water. (* 100 L of bait spray will treat 10 ha of mango trees).

If using maldison of 500 g/L strength then use 870 mL instead of 435 mL in 100 L of spray.

Application of the bait onto the developing fruit has been reported to burn the skin of the fruit. It
is best applied on the southern side of the tree and inside the trees to avoid sunlight or onto
pieces of hessian hung in the trees. The same area should be targeted each time to avoid
extensive fruit damage and to encourage a build up of bait on the tree.

DISEASES

Anthracnose (Colletotrichum gloeosporioides) is a fungal disease that is a major problem
under wet humid conditions. Wet weather favours the development, dispersal and germination
of spores and the consequent infection of plants. The Top End has the advantage that flowering
and fruit set occur during the dry season and this greatly reduces the incidence of flower and
early fruit set anthracnose. Unseasonal rain or foggy or dewy conditions at this time may favour
anthracnose development and it may be necessary to spray with mancozeb (2 g/L) at weekly
intervals until fruit are about the size of a 20 cent piece. These early spray applications are
necessary where mango scab occurs. After this stage, copper sprays are recommended –
either copper hydroxide at 2 g/L or copper oxychloride at 4 g/L. These give effective control of
both anthracnose and scab. The disease can also penetrate green fruit and remains dormant
until ripening when the lesions appear. The grower seldom sees this as this stage develops
some time after harvest when the fruit reaches the market. Post harvest dips are usually
effective in controlling this problem - see later section, Post Harvest Treatment. For further
details see Agnote No. I23 “Mango Anthracnose”.

Stem end rot (Botryodiplodia theobromae) is a post harvest fungal disease, which usually
builds up in orchards as trees age. Symptoms appear as fruit ripen. A brown discolouration and
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rot starts at the stem end and develops rapidly over the skin and through the flesh. It can
develop away from the stem end at any injury site on the fruit. Infected fruit has an unpleasant
flavour. The fungi build up on dead twigs, branches and leaf litter where they produce large
numbers of spores. The spores prior to harvesting can infect flowers and developing fruit.
Placing fruit stem end down on the ground under trees after picking can also promote infection.
Pre-harvest sprays of copper oxychloride, used to control bacterial black spot, or mancozeb for
anthracnose control, may reduce the incidence of stem end rot in fruit. Other methods of control
are to avoid harvesting immature fruit, cooling of fruit immediately following harvest and storage
in well-ventilated containers. Post harvest dips can also give some control.

Mango scab (Elsinoë mangiferae) is a fungal disease. Its main commercial effect is the scarring
(scab) which appears on infected fruit. In severe cases the fruit is unmarketable. The treatment
is the same as for anthracnose, but copper appears to give better control than Mancozeb®. For
more details see Agnote No. I33 "Mango Scab and its Control".

Bacterial black spot (Xanthomonas campetstris) occurs as multiple small black gummy spots
on the fruit. Diseased trees have an unthrifty appearance, leaves have dark angular raised
spots with a yellow halo, and infected branches have small swollen longitudinal cracks, dark in
colour, often filled with gum. The disease is spread by infected plants and scion material taken
into new areas. The infection is spread onto the fruit by windy and rainy conditions. If infected
trees are in the orchard, pre-harvest control measures are needed. Monthly sprays of copper
oxychloride or copper hydroxide should help control any outbreaks. Avoid spraying at flowering.

HARVESTING

Marketing immature fruit damages future sales potential.

Harvesting usually begins in late September to early October The earliest fruit on the market
usually commands premium prices (depending on quality). To this end it is advantageous to
pick fruit soon after it reaches maturity. This also ensures that fruit has the maximum shelf life.
Fruit left too long on the tree, until it has already started to soften, will not travel well (bruises
easily) and lacks shelf life. Immature harvested fruit shrivels and softens but does not develop
flavour, and is either rejected at the market place or receives very low prices.

Flowering and fruit-set normally occur over a three to four week period resulting in the fruit on
any one tree being at various stages of maturity. Depending on the flowering, the crop can
usually be harvested in about three picks (for any one variety). Harvesting usually begins about
early to mid October in the Top End with a light first pick of early fruit, about 10-20 % of the
crop. The second pick a couple of weeks later is generally the heaviest, about 40-70% of fruit
being mature. A final pick about a week later should catch the late set fruit.

FRUIT MATURITY INDICATORS

Non-destructive indicators:

•   Skin colour changes from dark green to light green.
•   Skin texture changes from rough/coarse to a smooth tight appearance.
•   Shoulders fill out - peduncle sinks (Kensington Pride variety).
•   Beak at bottom of the fruit fills out.
•   Note flowering date when panicles open - fruit take about 100-110 days to reach maturity.
    (This can be quite variable depending on weather conditions).
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Destructive methods of checking maturity:

•   Cutting open fruit, if the flesh is starting to go yellow as opposed to white, it is reaching
    maturity. Butter yellow is a good indicator that fruit is ready and mature.
•   Dry matter testing is the most reliable method. The minimum acceptable dry matter level for
    all markets is 14%.

DRY MATTER TEST

Do samples in duplicate, if the difference is greater than 0.5% repeat the test. Accurate scales
(to 0.01g) are needed.

1. Select 3 - 5 of most mature looking fruit for testing.

2. Record date, variety and block for future reference.

3. Cut off both cheeks, cut in half and keep half from each cheek for sampling. Grate samples
   using a carrot grater onto a china plate. Mix up grated fruit.

4. Using two patty cups (one inside the other), weigh exactly 10 g and record. (Use two to
   prevent the cups sticking to the oven plate). On the beam balance scales, put the weights
   into two pattypan cups so that the weight of cups is balanced out, using tweezers to
   accurately weigh in 10 g.

5. Place in a microwave with a cup of water (half-full so it does not boil over). Set microwave
   to medium or medium-low for 30-40 minutes. The setting and the time vary with each
   microwave. Set the microwave so that the sample is lightly browned not black. The setting
   varies with the number of samples. Check that the water does not dry out.

6. The sample(s) should be monitored frequently. When they begin to go brown and start to
   dry out they should be weighed every 2-3 minutes.

7. The sample is dry when it no longer changes weight. The weight of the dry sample x 10 is
   the dry matter percentage.

Note: It is important not to burn the samples while drying in a microwave oven. At the same
time, the samples should not be under dried. It is desirable to calibrate the technique to the
microwave being used. Drying in hot air oven at 65°C for 24 hours is safe and does not burn the
samples even if left for a longer duration. This technique is slow but more reliable. For further
details, contact the DPIFM Horticulture section.

It is not necessary to do the dry matter tests often because dry matter increases by 0.7-
1%/week.

SAPBURN

Sap can burn the skin of mangoes. Although the damage is not immediately apparent,
blemishes usually appear some days later when the fruit arrives at the market. There are a
number of treatments to reduce the incidence of sapburn.

De-stemming and de-sapping:
                                                   8

Detergent Dip is the easiest method. The rate for Septone Mango Wash® is 200-300 g/100 L of
water. The fruit is de-stemmed outside the tank, allowing all the spurt sap to finish before
placing the fruit in the tank with the solution. The fruit is left in the tank for one minute (if left in
the solution too long skin marking could occur). Because the chemicals in the dip break down
during use, it is recommended that 200 kg of fruit will require 100 litres of dip. The dip must then
be replaced. Rinse fruit with clean water after removing from the mango wash.

Drain Rack/Webber Tray use requires care to be taken placing fruit on the racks ensuring that it
does not fall over. Fruit is placed on the racks stem end down and the stem is snapped off. The
fruit is allowed to drain for a couple of hours before dipping and packing. If possible fruit should
be hosed down regularly and racks washed between batches. The hands of the operator should
also be rinsed in detergent to avoid contaminating fruit with sap.

D.C. Tron®/Bioshield Oil® is made using a solution rate of 10 - 20 mL of oil /100 L of water. Fruit
can be either dipped in the solution for 30-60 seconds, then de-stemmed onto racks, without
hosing off or de-stemmed and placed stem end down on rollers passing under sprays. Fruit
should be totally covered by the mix and remain wet for about 30-60 seconds. The solution
should be continuously agitated. Do not treat fruit dipped in oil with hot water. High rates of oil
can cause blotchiness on ripening fruit. Replace the mix at the rate of 200 kg fruit/100 L.

Picking method:

•   Harvest in the morning when fruit is cool.
•   Keep harvested fruit out of the sun.
•   Use secateurs, or for higher fruit a picking pole with the grip/cut action, which holds the fruit
    by the stalk, after it has been cut.
•   Fruit should be handled with care at all times. Hard green fruit dropped from a height
    greater than 30 cm, onto a hard surface e.g. a branch will suffer from internal cracking and
    will not ripen satisfactorily.
•   Pick with long stems 10 cm or more and lay fruits on their sides in the crates to reduce stem
    breakage and contamination by sap.
•   Clean crates and equipment regularly; wash in detergent (Mango Wash®).
•   Have detergent handy to wash hands and equipment in the field and to dip fruit with broken
    stems in detergents, these fruit should be kept in a separate crate and marked accordingly.
•   If carting over any distance, cover crates, as dust abrasion can be a problem.
•   After rain postpone harvesting for at least three hours of sunshine to dry out fruit. Skin is
    susceptible to handling marks after rain.
•   If possible de-sap in the orchard into Mango Wash®.

HARVEST TO MARKET

Post-harvest handling and treatments for sap burn, pests and diseases, storage and transport
and quarantine requirements are major management issues from harvest to market.

POST HARVEST TREATMENT

After harvesting the fruit should be given a quick rinse with a hose to remove any dust or
accidental sap on the skin (this prolongs the life of dips by reducing the source of
contamination). As stated earlier, the fruit should be de-sapped.
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Anthracnose and stem end rot (Botryodiplodia theobromae) are the most important post harvest
rots found in mangoes. Both develop in ripening fruit, so are not noticed in the grading and
packing process. The fruit can be dipped as a precaution against these rots.

There are two methods:

a. Hot benomyl dip controls anthracnose and partially controls stem end rot. Fruit should be
   stored for 12 - 16 hours before dipping to prevent scalding. Rain within 36 hours of harvest
   increases the risk of scalding. Do not dip fruit treated with oil at de-sapping.

b. Hot benomyl dips should be applied before dimethoate. The fruit is totally submerged for
   five minutes in hot water (52°C) to which 100 g/100 L of benomyl 50% (Benlate®) has been
   added. The temperature must be carefully maintained; too high a temperature will damage
   fruit and too cool will reduce effectiveness. The dip must be constantly agitated to prevent
   the fungicide settling to the bottom. The dip should be replaced every three days or sooner
   with a fresh batch, if heavy contamination occurs from sap and dirt.

c.   Unheated prochloraz can be used as a non-recirculating spray. This is not effective
     against stem end rot, and at present is not approved as a dip. Solution concentration should
     be 250 ppm. This can be achieved by using 55 mL of Sportak® (45% prochloraz) per 100 L
     of water. Prochloraz is compatible with fenthion and should be mixed with it and applied as
     a low volume non-recirculating spray. See appropriate fruit fly treatment for application
     method.

All mangoes sent out of the Territory should be dipped for fruit fly, even if treatment is not
required at the state or country of destination. If any infested fruit is found at the other end, the
whole consignment will have to be treated, or condemned and destroyed which can be costly.

Fruit Fly Treatments
Interstate Certification Assurance requires post harvest treatment of all mangoes by one of the
following three methods:

1. Full immersion of fruit for 60 seconds in a mixture containing either

•    dimethoate @ 400 ppm = 100 mL/100 L water of a 400 g/L dimethoate formulation; or
•    Fenthion @ 412.5 ppm = 75 mL/100 L water of a 550 g/L fenthion formulation.

Dips should be replaced every five to seven days or sooner if they become contaminated from
dirty fruit.

2. Flood spraying fruit with either of dimethoate or fenthion at the above concentrations. The
   mixture is applied to fruit over rollers at a rate of at least 16 L/minute per each square
   metre. Fruit must be fully covered by the spray for 10 seconds and then remain wet for a
   further 60 seconds. Replace spray mix as for dips above.

3. Low volume non-recirculating spray using fenthion at the above rate. The mixture is
   applied to fruit over rollers at a rate of at least 1.2 L/minute per each square metre. Fruit
   must be fully covered by the spray for 10 seconds and then remain wet for a further 60
   seconds.
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Always use fresh chemicals, or have them checked if they have been stored for some time,
especially dimethoate. Dips and mixtures should be checked regularly to ensure concentration
is correct. Fenthion and prochloraz mixes should be constantly and vigorously agitated to
prevent them settling out.

Fenthion and prochloraz are compatible and may be sprayed together as a non-recirculating
spray.

Dimethoate dipping facilities should be situated in a well-ventilated area or outside as the smell
can be overpowering in an enclosed area.

All fruit fly chemicals should be applied as the last treatment before packing and should
dry on the fruit.

All chemicals used for spraying or dipping fruit must be disposed of safely. For details
see Agnotes No. I31 “Dimethoate as a Postharvest Treatment”.

Fruit fly hot water dips have the advantage of also controlling anthracnose and to some extent
stem end rot, and are non-chemical, which is necessary to export to certain countries.

Fruit is submerged in water at 47°C for 60 minutes, then removed and cooled rapidly in cold
water.

To reduce the incidence of scald damage to fruit, follow these procedures:

•   Cut off or significantly reduce irrigation at least two weeks before harvest.
•   Harvest only mature fruit for hot water treatment.
•   Do not use oils for de-sapping.
•   Delay treatment for up to 24 hours after harvest.
•   Where rain falls within 48 hours of harvest or trees are irrigated fruit should be held for at
    least 24 and preferably 48 hours after picking.
•   Ensure the dip tank has a good circulatory system.
•   The water temperature must not exceed 47.5°C.
•   The dip time should not significantly exceed 60 minutes.

PACKING

Dipping costs time and money. Cull-out reject fruit before dipping, preferably in the field by
pickers.

Large producers will need access to a grading machine and even smaller producers may find it
advantageous to pay for the use of a grader. There are a number of different types on the
market. The preferred type at the moment grades by the weight of the fruit, although size
graders are quite satisfactory.

Always hold back some fruit from each consignment, preferably one or two cartons to check
turn out. These should be held at 20°C and monitored for any problems during ripening, such as
development of sap burn, fruit rots and abrasions.
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Fruit should be graded and packed into trays according to the following criteria:

•   Variety.
•   Firm non ripening.
•   Uniform size and shape.
•   Freedom from blemishes.
•   Uniform colour.

Mangoes are hand-packed in single layer fibreboard trays. Plastic and papiermâché inserts with
moulded cups or channels are available in a range of counts. (The most commonly used vary
between 10 for large fruit to 20-25 for smaller fruit). These inserts help speed up the packing
process. Trays also come in different depths to accommodate larger fruit. Fruit should be
packed stem end down to prevent any latent ooze sap damaging the skin. Trays should be
packed so that the fruit are holding each other firmly in place, with no movement when the lid is
closed, and should weigh at least 6.8 kg. A carton can lose around 400 g in transit resulting in a
very loose pack at the market. After transit a standard carton should weigh 6.5-7 kg.

This method is costly both in carton cost per kilogram of fruit as well as time and labour. A cost
saving method would be by volume filling large cartons. Using this method fruit is still graded to
size but the carton is simply filled until a required weight is reached. Trials using 10 kg and 18
kg cartons transported by refrigerated trucks arrived at southern markets in good condition of
both fruit and cartons. Despite the fact that the mangoes were in good condition, prices received
were relatively low. This may be the way to send consignments to supermarket chains and other
bulk purchasers in the future, but at present the highest prices are still received for trays.

LABELLING

Growers packing mangoes for sale on the domestic markets must mark on the end panel of the
box the following information:

•   The name of the grower or packing establishment together with the address i.e. lot number,
    street/road and area, not the postal address.
•   The name of the consignee.
•   The mango variety, class and count if packed in mango cartons.
•   The words “Meets ICA-19”.
•   Packer I.P. No:
•   Grower I.P. No: (if grower is a different business to packer).
•   Date (or date code) on which fruit was packed.

Fruit in bulk packs must have the weight shown instead of count number.
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STORAGE/TRANSPORT

Immediately following picking, the supply of "food" and water to the fruit is cut off and
senescence begins. The rate of senescence depends on the rate of respiration, which is
governed mainly by temperature. To effectively slow down ripening, pulp temperature of fruit
should be cooled to 13–15°C within 12-15 hours of harvest. Dropping the temperature of the
fruit from 27°C (early morning ambient temp) to 13°C will delay by three times the length of time
the fruit will take to reach eating ripeness, e.g. from seven days to 21 days. The quickest way to
achieve this is by forced air cooling, in a cool room designed for this purpose.

Cool rooms for fruit and vegetables should be designed for high humidity 85% + or dehydration,
shrinkage and softening of produce may result.

Chilling injury occurs at temperature below 13°C. This results in uneven ripening, off flavours,
poor quality and often unsaleable fruit. However fruit may be stored for short periods, less than
seven days at 11°C without being affected.

Optimum ripening temperatures are 16°C for skin colour and 27°C for flavour. As a compromise
fruit may be ripened at 18-22°C.

Ripe mangoes will maintain good quality for up to seven days in a domestic refrigerator at 3-5°C
provided they have no infections.

Other factors affecting storage life are:

•   Pest and disease infection; control methods have been mentioned previously in this
    Agnote.
•   Impact damage, mature green fruit will crack internally and ripe fruit will bruise if dropped
    more than 30 cm onto a hard surface. This includes fruit in packages.
•   Abrasion damage caused by loosely packed fruit rubbing together during transportation;
    worn brushes on grading machinery can also damage fruit. The damaged area not only
    detracts from the appearance of the fruit but can be a source of infection.
•   Pressure damage caused by over filling packages, package failure due to over stacking
    (collapse of bottom layers) and moist cartons losing compression strength when stacked.
    Fruit should not be stored in bulk bins for more than 10 days or the bottom layers will be
    damaged. Fruit stored for up to 21 days at 13°C should be limited to a depth of three layers.

To minimise handling of produce, trays can be stacked on pallets (ensure the air slots in the
ends of cartons are lined up to allow air movement through the stack). If air movement is
restricted by incorrect stacking the temperature at the centre may actually rise due to the build-
up of respiratory heat. The maximum height for stacking fibro single layer trays is 15 layers with
eight trays per layer on pallets. Packages should be stacked on a pallet in such a way that there
is no gap between the cartons and the edge of the pallet. To secure packages to the pallet,
tension nets, corner angles, horizontal straps or palletising glue and tape are the most effective
methods.

At the market best prices are paid for fruit which is "on the turn", i.e. nearly ready to eat. Fruit
arriving in a green state can be held over for a number of days till the agent considers it is ready
for sale. Ideally, fruit sent by airfreight to southern markets should be semi-ripened prior to
loading. It should not be necessary to refrigerate, as it will soon be on the market. This method
                                                  13

is suitable for early fruit trying to catch the high prices. To speed up the ripening process the
fruit can be gassed with ethylene.

Due to high costs and limited space, air freighting has its limitations. With the increased
production in mangoes road freight is the only practical means for growers to get fruit to
southern markets. However there are a number of options:

1. Pre cool fruit to 20°C, ripen, using ethylene gas, and transport ripened fruit in a refrigerated
   truck at 13-15°C.

2. Pre cool fruit to 20°C. Transport in refrigerated truck at 18-20°C.This gives fruit a chance to
   ripen en route to the market.

3. Pre cool fruit to 13-15°C and transport in an insulated but non-refrigerated truck. Fruit
   should arrive at the market, beginning to show signs of ripening. Using this option, it is most
   important that fruit is pre-cooled before loading.

The success of options 1 and 2 would depend on the maturity of the fruit being above 15% dry
matter (butter yellow flesh colour). Fruit picked at a lower maturity level will take longer to ripen.

Trucks can reach Sydney and Melbourne in about four days. This allows a good margin of time
to consolidate a load, arrange transport and still have good storage life after reaching the
markets.

ETHYLENE RIPENING

The ripening process can be triggered in mature fruit causing it to ripen within five to nine days.
This is an option open to growers, which ensures fruit arrives at the market in a ripe condition,
and could be useful for air freighted fruit. However growers must ensure fruit which has been
ethylene treated is kept refrigerated and reaches the market within this period, as ripe fruit does
not transport well by road.

•   When using gas, it is necessary to use an air-tight ripening room, with temperature control
    to 20°C and 85% humidity,

•   Fruit should be exposed to gas for 24 hours; this triggers the ripening process.

•   Only mature fruit should be gassed, the more mature the fruit (dry matter above 14%) the
    shorter the time to ripening. Immature fruit will change skin colour and get soft, but the
    flavour will be poor.

•   After gassing, fruit must be kept at 18-22°C, even during transport as it may heat up during
    the ripening process.

After gassing, fruit will ripen in five to nine days, at these temperatures.

There are a number of methods of gassing fruit:

Shot Method
• Ethylene gas is injected into the room at 200 ppm.
•   Two shots are applied over the 24-hour period.
•   The room must be completely ventilated between shots.
                                                       14

Trickle Method
• Ethylene gas is injected constantly into the room at a concentration of 10 ppm.
•   It is necessary to calibrate the leakage rate of the room. Contact the Chemistry Branch of
    DPIFM.

INTERSTATE AND OVERSEAS QUARANTINE REQUIREMENTS

As these can change quite frequently, growers should contact the Agricultural Quarantine
Inspection Service at Berrimah Farm before harvesting each year to check requirements. The
AQIS phone number is 8999 2311.



Please visit us on our website at www.primaryindustry.nt.gov.au




Published: Monday 13 December 1999.




While all care has been taken to ensure that information contained in this Agnote is true and correct at the time
of publication, the Northern Territory of Australia gives no warranty or assurance, and makes no representation
as to the accuracy of any information or advice contained in this publication, or that it is suitable for your
intended use. No serious, business or investment decisions should be made in reliance on this information
without obtaining independent/or professional advice in relation to your particular situation.

								
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