2020 – Page 9 – Sub-Tropical Fruit Club of Qld Inc.

Asimina triloba – American Pawpaw

Sheryl I bought back some seed from California given to me by Roger Meyer – really enjoyed the taste of the fruit. Kentucky State University area conducts cultivar testing and growing in an experimental orchard and they have an excellent website: www.pawpaw.kysu.edu John Prince, one of our members in New Zealand says he made one of his best ever ice-creams from this fruit.

Kentucky State University has the only full-time Asimina triloba (L.) Dunal research program in the world as part of the KSU Land Grant Program. Research efforts are directed at improving seed and clonal propagation methods, developing orchard management recommendations, conducting regional variety trials, understanding fruit ripening processes, developing fruit storage techniques, and germplasm collection and characterization of genetic diversity. KSU is also the home of the PawPaw Foundation, a nonprofit organization dedicated to the research and development of Asimina as a new fruit crop. (Asimina is known as PawPaw in the USA).Contact Dr. Kirk Pomper: kpomper@dcr.net

The USDA National Clonal Repository for Asimina spp. Since 1994 Kentucky State University has served as the USDA National Clonal Germplasm Repository (NCGR), or gene bank, for Asimina spp. as a satellite site of the NCGR repository at Corvallis, Oregon. There are over 1,700 accessions (trees) from 17 states that are planted on 8 acres at the KSU farm and they are attempting to evaluate the genetic diversity contained in wild Asimina populations across its native range so that unique material can be added to the KYSU repository collection; this potentially rich source of useful genetic traits will be used in breeding efforts.

Climate Asimina is a tree of temperate humid growing zones, requiring warm to hot summers, mild to cold winters, and a minimum of 32 inches (81 cm) of rainfall spread rather evenly throughout the year, with the majority falling in spring and summer. It can be grown successfully in USDA plant hardiness zones 5 (-15^o F/-26^o C) through 8 (15^o F/-9^o C). They grow wild over a wide range of latitude, from the Gulf Coastal plain to southern Michigan. However, the trees may not receive adequate chilling hours if planted too close to the Gulf Coast. Most named cultivars originated in the Midwest, which is the northern portion of the Asimina’s range. A national regional variety trial is underway to determine which varieties perform best in different parts of the country, and results should become available in the next several years. In the meantime, for best results, choose cultivars that were selected in a climatic zone and latitude similar to the area where they will be planted.

Site, soils, and habitat Although the Asimina is capable of fruiting in the shade, optimum yields are obtained in open exposure with some protection from wind (on account of the large leaves). Germinating seedlings, however, will not survive under those conditions because they are extremely sensitive to full sunlight which can kill them. (Containerized seedlings may be grown without shade in a greenhouse.) Shading for the first year and sometimes the second is normally required outside and it is for this reason that Asimina are almost always found in nature as an understorey tree. The soil should be slightly acid (pH 5.5-7), deep, fertile, and well-drained. Good drainage is essential to success. Asimina will not thrive in heavy soil or waterlogged soil. In habit it is a small tree, seldom taller than 8 mtrs. – 25 feet. Grown in full sun, the tree develops a narrowly pyramidal shape with dense, drooping foliage down to the ground level. In the shade it has a more open branching habit with few lower limbs and horizontally held leaves.

Seed Propagation The seed is slow to germinate but it is not difficult to grow seedlings if certain procedures are followed. Do not allow the seed to freeze or dry out, because this can destroy the immature, dormant embryo. If seeds are dried for 3 days at room temperature, the germination percentage can drop to less than 20%. To break dormancy, the seed must receive a period of cold, moist stratification for 70-100 days. This may be accomplished by sowing the seed late in the fall and letting it overwinter; the seed will germinate the following year in late July to late August.

Another way is to stratify the seed in the refrigerator (32^o– 40^o F/0^o– 4^o C). In this case the cleaned seed should be stored in a plastic ziplock bag with a little moist sphagnum moss to keep the seed moist and suppress fungal and bacterial growth. After stratification the seed should be sown 1 inch (2.5 cm) deep in a well-aerated soil mix, pH 5.5-7, with an optimum temperature of 75^o– 85^oF (24^o– 29^oC). Use tall containers, such as tree pots (ht. 14″-18″/35-45 cm) or root trainers (ht. 10″/25 cm), to accommodate the long taproot. The seed will normally germinate in 2-3 weeks, and the shoot will emerge in about 2 months. Germination is hypogeal: the shoot emerges without any cotyledons. For the first two years, growth is slow as the root system establishes itself, but thereafter it accelerates. Trees normally begin to bear fruit when the saplings reach 6 feet, which usually requires five to eight years.

Vegetative or clonal propagation Clones are easily propagated by a number of grafting and budding techniques, such as whip-and-tongue, cleft, bark inlay, and chip budding. The only method that does not produce good results is T-budding. Softwood and hardwood cuttings have proved virtually impossible to root. Although it is common for the tree to sucker from the roots, propagating a clone by transplanting root suckers is often not successful. They are ordinarily quite difficult to transplant. They have fleshy, brittle roots with very few fine hairs. Experimentation has shown that, to be successful, transplantation should be done in the spring at the time that new growth commences, or soon after. (This is basically the same as for magnolia.) If many roots are lost, it may be desirable to prune the top to bring it into balance with the remaining roots. Grafted trees may bear fruit in as few as 3 years.

Purchasing trees Since seedlings are not identical to their parents, fruit quality cannot be guaranteed. Since they retain the clonal identity of the parent, fruit quality is assured, given adequate cultural conditions. If fruit production is desired, purchase at least two genetically different trees (i.e. two different cultivars, or at least two seedlings), to ensure that cross pollination can occur. Container-grown trees may have a higher establishment (survival) rate than field-dug trees; Asiminas have a long tap root and delicate root system that can be damaged by digging.

Caring for young trees When planting trees, allow 8 feet (2.5m) between them. Water newly planted trees immediately after planting, and as needed throughout the growing season. Trees require adequate soil moisture, especially in the first two years after planting. Transplant shock may be reduced by providing temporary partial shade to newly planted trees. Application of a balanced fertilizer (20N-20P-20K) every few weeks during the first half of the growing season may also improve growth and establishment of young trees.

Pollination: natural and artificial Pollination can be a limiting factor in Asimina fruit set. The flowers are protogynous, meaning that the stigma (the female receptive organ) ripens before the pollen, and is no longer receptive when the pollen is shed. Thus the flower is designed not to be self-pollinated. In addition, the trees are self-incompatible, usually requiring pollen from a genetically different tree in order to be fertilized. Finally, the natural pollinators of the Asimina –various species of flies and beetles–are not efficient or dependable. Although it requires a little extra labour, hand pollination to ensure fruit set can be well worth the effort and can be done as follows: Using a small, flexible artist’s brush, transfer a quantity of fresh pollen from the anthers of the flower of one clone to the ripe stigma of the flower of another clone. Pollen is ripe when the little ball of anthers is brown in colour, loose and friable; pollen grains appear as yellow dust on the brush hairs. The stigma is ripe when the tips of the pistils are green and glossy, and the anther ball is still hard and green. Do not overburden the tree with fruit, as this will stress the tree, resulting in smaller than normal fruit, and may cause limbs to break under excessive weight.

Pests In its native habitat the tree has few pests of any importance. The worst pest is Talponia plummeriana, the Asimina peduncle borer, a small moth larva (about 5 mm long) that burrows into the fleshy tissues of the flower, causing the flower to wither and drop. In some years this borer is capable of destroying the majority of blossoms. Another pest is Eurytides marcellus, the zebra swallowtail butterfly, whose larvae feed exclusively on young Asimina foliage, but never in great numbers. The adult butterfly is of such great beauty that this should be thought more a blessing than a curse. Sometimes the fruit surface may be covered with patches that are hard and black; this is a fungus infection, but it seldom has any effect on flavour or edibility. Deer will not eat the leaves or twigs, but they will eat fruit that has dropped on the ground. Male deer occasionally damage trees by rubbing their antlers on them in winter. Outside its native region, the tree is sometimes reported to be plagued by pests, but this may be because of poor tree health resulting from the stress of improper soils and an unsuitable climate.

Chester Dott – Forbidden Fruit Nursery – Mullumbimby: Plant it the same as papaya, good drainage; do not disturb the taproot.

Tom Ling: I have 4 seedlings growing in full sun through late Summer and Winter without any problem. 2 of them still have their first pair of leaves. The other 2 have lost the leaves in the Winter. I have others in full shade. The average temp in Winter here is 22C. There is a web page I read long time ago describing experiments on the effect of pot depth to the vigour in growth. It has a few photos showing seedlings with roots. All my 10 or so seedlings have varying length of tap roots. The longest one is about 15cm 4 weeks after casting off the seed pod. I also noticed that if a seedling has difficulty splitting and casting off its seed pod then it is most likely to have stunted malformed roots. You can try manually to split open the seed pod but you may end up breaking the tip. Some may try to grow again without the broken tip.

One technique to try to induce the splitting is to use a eye dropper to wet the seed pod constantly. I think it is best to sow directly in the ground as it doesn’t like transplanting from some other pages I read. But my experience is they don’t mind that at all. The seedling will lose all leaves in Winter and may appear dead with shriveled look on the stem but come Spring, the leaves will grow back. I use half plastic bottles to protect them from cold. Ignore what web pages say about sensitive to transplant and sunlight. Some seedlings do like sun but play safe in the first 2 years. Quite easy to transplant. Emerging seedlings have tap roots from 10 inches to a few inches depending on the robustness of the shoots. Seed pods will stick to shoot tips for 2 to 6 weeks or forever depending on the weather and health of the shoots. After 4 weeks if pods are still unopened, prise open with finger nails. If tips break as a result, keep the shoots over Winter in a neutral location outside. The broken tip shoot of 1 inch tall is capable of producing new branches in the coming Spring. This is one of the few species that can do this. Some seeds will lie dormant for 1 year before germinating.

Marcello: One reason I read for why this tree is hard to grow on a commercial scale is that when the tree’s female stigmas are ripe for pollination, male blooms are often just getting ready to manufacture pollen so it appears to be a question of ‘missed’ timing for extemporaneous pollination if left to nature’s devices to effect fertilization. In fact, crops are often hand pollinated to circumvent precisely this problem.

Sergio Duarte – Portugal: I am using custom made bags that are 60cm tall and I can tell you that the seedlings produce a tap root of at least 25cm in length, even before they produce the first pair of leaves. Some people state that with care it is possible to get Asiminas to live after the main tap root has been pruned so the tap root seems to be important but is not completely vital. I think the main problem is that Asimina triloba is said to require some winter chill to break dormancy. 100 hours was the number that came up on another forum when I asked about it but I don’t think anyone knows exactly how much for sure. You will have a better chance if you plant them at your highest elevation.

Mike Nave – Sacramento, California Despite their well known preference for water and preference for cool shaded and even wet areas, I have seedlings that do well with little watering (probably because of that taproot) and do not seem particularly affected by our summer heat and wind. My grafted ones do have problems with the heat here and are not exceptionally vigorous but the seedlings have virtually no problems at all. They grow well in heavy soil, light soil, pots etc. They will push the taproot through almost any pot in one season but I have experienced no problems with cutting the taproot to repot or to plant out.The only pests I have ever seen on my Asiminas are some small insect that snacks on the leaves when they are first emerging. Nothing seems to bother the leaves once they are mature. Snails will attack the fruit only if they suffer some kind of damage. Birds do not seem to understand that the fruits are food although they attack all other fruits on my property. Ants and aphids ignore the trees, although ants will infest the fruits if they fall to the ground and break open. I do occasionally get some kind of very small scale insect but it does no damage. Despite their well known preference for water and preference for cool shaded and even wet areas, I have seedlings that do well with little watering (probably because of that taproot) and do not seem particularly affected by our summer heat and wind. My grafted trees do have problems with the heat here and are not exceptionally vigorous but the seedlings have virtually no problems at all. They grow well in heavy soil, light soil, pots etc. They will push the taproot through almost any pot in one season but I have experienced no problems with cutting the taproot to repot or to plant out.

Elwyn Hegarty: This is the plant known as Pawpaw in the States that has been credited with some anti-cancer qualities. There has been considerable confusion because of the common name and the fact that Asimina is in Annonaceae and no relation to what we would call Pawpaw (Carica papaya, Caricaceae) here in Australia. Both come from parts of tropical America. This confusion was compounded a few years ago when New Scientist published a letter about Asimina illustrated by a photo of Carica papaya – they did correct this in the next edition, though. We had occasion to look into this scene about the same time for a client who was using papaw leaf and tried to find out whether any of the health claims then being made for our papaws had been confused with those then being validated for Asimina, as seemed possible. Both contain bioactives in various parts of the plant. If the medicinal use of Asimina comes up, as it probably will if you are distributing seed, perhaps we’d better take another quick look at the information we had found at the time, and then see what’s been discovered about medicinal qualities of both plants in the interim – you may have updates following your trip, too. (There’s the same problem with cat’s claw herbals, at least two different, unrelated, plants are known as cat’s claw).

Notes from Donald Cobb in The Nutshell (Northern Nut Growers Association Sept.1998) I attended my first meeting of the above association and learnt about meristematic dieback of greenhouse grown Asimina. If after planting your seed and the seedlings have that wilted look in our hot weather, it could be suffering from too high a soil pH. If it’s around 6.8, it’s too high. Not having sulphuric acid on hand or the mathematical background to do calculations for its use, I decided to use what I had at hand to acidify the soil; white distilled vinegar and a soluble complete fertilizer formulated for acid loving plants. I added 1/3 cup vinegar and 5 tablespoons of fertilizer to 20 litres of water. I saturate-watered the Asimina seedlings with this solution and again a week later. Four days after the first watering, the seedlings new leaves were erect and bright green. Two weeks after the second soaking, the seedlings health and vigour were much improved and the soil pH tested 5.8. Some of the seedlings had doubled in size in just three weeks. I am sure I would have lost many of these seedlings if I had not acidified the soil.

Just remember that when planting seed, they require a very very deep pot.

Article collated by Sheryl Backhouse

Mangosteen and its relatives

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This family is made famous by the Purple Mangosteen (Garcinia mangostana) of the Malay peninsula. Considered by many to be the best fruit in the world and by most Asians to be the second best after the Durian. At this time I don’t know of any successful attempts to grow the tree in S.E. Qld. The growing of this tree has been the Holy Grail for some growers in our area and other simular climates around the world. This is a very tropical tree, in Florida there was supposed to be one tree that produced one fruit and then died. Doesn’t give much hope, does it. We probably do have a better chance, as we don’t have their occasional severe frost.

As a young boy I lived in Malaya for 6 years and I use to climb through the trees and eat the fruit regularly; the skin stained my clothes a greeny brown that didn’t wash out. You could make the best sling shots from the branches, the side branches came out at about 40 degs and you could bend and heat them and they kept their shape on cooling. These thin branches had tremendous strength, that’s what I remember! I don’t remember thinking that the fruit was any more than very nice though. There is a lot of other fruit in the family that can grow here with ease, and others that shouldn’t be too difficult. Most are sour, but some are quite palatable. Here is a list of some with info from different sources:

Mundu (Garcinia dulcis) I have one growing which I bought years ago; it is very simular to the Yellow Mangosteen. The fruit is not as sour; Sheryl liked it and she normally likes sweet things. One to two seed, 100 mm dia and it is not affected by the fruit fly. Our tree started producing fruit about year 7; this year it has produced about 40 fruit. It is reputed to have health benefits. I think it is like others in the family & has antibiotic benefits going by how well it keeps. The tree is pyramidal in shape with long leaves hanging down in pairs. Leathery and dark green with the young leaves being pink/red. A nice tree that is very tolerant of shade. Mine grows in the sun and is taking it well. It’s about four metres tall and is nine years old approx.

Yellow Mangosteen, Gamboge (Garcinia xanthochymus). This produces heavy crops of very sour fruit, although the flesh surrounding the 2 seeds is to me quite nice, (but I like lemons). There appears to be no pest problems in S.E. Qld. I have seen them growing in full sun in exposed positions, these had yellow leaves. At the opposite end of the scale in the deepest of shades in the Brisbane botanical gardens, these had dark green leaves. In all case they produced very heavy crops. They are very drought hardy but they probably would not take to much frost. This tree grows from Malaysia to India and is used for food, medication and colouring.

Other trees closely related to the purple mangosteen that are growing in or around S.E. Qld:

Bacupari (Rheedia brasiliensis) This is growing well in our garden, 1.5 metres high in 2 years. Supposed to be subacid and good eating.

Madrono (Rheedia madruno Rheedia acuminata) Cold hardy to 0 deg C. Thick yellow skin. Tangy aromatic, eaten fresh. Likes sweet soils. I have 2 trees labelled Madrono about 1 metre after 3 yrs. Should be one for us. South America

Madronio (Rheedia magnifolia) Another fruit with the same common name, my trees look different so who knows. Supposed to be very good, reasonably sweet with a bit of tang. Smooth skinned. South America.

Imbe (Garcinia livingstone) 25 to 30 mm. Hardy –2 deg C. Some say little flesh others worth growing. Taste is good. Thin skinned. Sun or shade, likes even water supply. There is a specimen in the Brisbane Botanical Gardens that has never impressed me, it looks very strange. East Africa

Mamey Apple Apricot of Santo Dominingo(Mammea americana). Good tasting fruit 100 to 200 mm. Thick leathery brown skin. 80 to 175 mm. Firm orange flesh, apricot flavoured in selected varieties. This one is a big tree, that grows well here. Seedlings can be male so get a grafted named variety. A very attractive tree. One of our members in the Glasshouse area had one growing, but it was a male as was all that batch that came down from the north at that time. Caribbean, Central America and Northern South America.

Some of the many others, in the family that sound good, but not sure of their cold tolerance:

Button Mangosteen or Cherapu (Garcinia prainiana)

Small fruit 40mm Sweet sour taste, acid pericarp , subacid pulp. Orange colour. Fruits early. Eaten fresh. From Thailand, Malaysia.

Brunei Cherry (Garcinia parvifolia) 1.5 cm fruit, red to yellow skin and a juicy, slightly tart white pulp. Sound good, but don’t know what its climatic tolerances would be. Borneo and Malaysia

Cochin gorka. Garcinia pictorius – Nice acid flavour. Eaten out of hand. Southeast Asia.

Cherapu. Garcinia prainiana – Sweet sour taste.. Eaten out of hand. Malaysia.

Gatdsan Garcinia venulosa -. Eaten out of hand, sourish taste. Southeast Asia, Philippines.

Goraka Garcinia cambogia – Eaten out of hand good subacid flavour. Also used in cooking Fruits are eaten as an appetizer, having succulent yellow pulp and a pleasant subacid flavor. Sri Lankan, Tropical Asia.

Garcinia hombroniana – This is the one which should be good. Peach like, eaten out of hand. Don’t know if it will grow here but worth a try. One of the parents of the Purple Mangosteen its thought. Malaysia.

Garcinia indica – Subacid pleasant fruit. Purple in colour. India

Garcinia cochinchinensis – plum size, reddish-yellow’, Subacid and juicy. Eaten out of hand.

Indian gamboge tree Garcinia morella -. Eaten out of hand. Small fruit.

Bunag Garcinia benthami -. Eaten out of hand, small fruit . Nice fruit. Subacid. Malaysia.

Asum gelugur Garcinia atroviridis –This one sounds simular to the Yellow Mangosteen. Tropical Asia.

Rheedia edulis – The oval, yellowish or orange fruits are eaten, having white flesh and an agreeable acid flavour. Often used for making jams. Cultivated locally, especially in Brazil. Central America. Rheedia macrophylla. 75mm fruit. Good flavour, eaten out of hand Brazilian Amazon.

Mango – Julie, a great mango to add to your collection

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One of our members is having it propagated as he enjoyed it so much. Originally known as the St. Julie Mango, now it is known simply as Julie. It is by far the most popular Mango in Jamaica and one of the most popular ones in the Caribbean countries. Julie is the main mango exported from the West Indies to Europe. Lawrence Zill, the famous Mango breeder of Boynton Beach, Florida had developed a much superior Mango “Carrie” from “Julie”.

Julie is characterized by its relatively small size, somewhat flattened shape and some purple like colour in the skin when ripe. Julie’s drawback of a short shelf life and good amount of fibre content is compensated for by its very sweet and juicy flesh and its wonderful flavour. ‘Julie’ on a scale of one to ten Jamaicans rate this is a solid twelve. Florida’s humidity makes this tree a challenge to grow however. Fungus problems which lead to twig dieback are common making fungicide applications necessary for success. The fruit itself is sweet and tangy having somewhat of a pineapple flavour. It is sought after for its dwarf growing habit.

Olive – What Cultivar is That?

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Different cultivars have different characteristics so correct cultivar identification is important.
An Australian report relating to olive cultivar identification, ‘Olive Oil Yield, Quality and Cultivar Identification’ by Kevin Robards and Rod Mailer, can be found at https://rirdc.infoservices.com.au/items/01-023. The research described is the start to ongoing work with the aim to develop DNA testing to identify olive tree cultivars (clones/ near clones) and to determine relatedness of different olive cultivars (see dendrogram Fig 5). Cultivars from the Wagga Wagga Olive Grove (WWOG), situated on the campus of Charles Sturt University and a grove at Yanco were used in the study. The findings were especially interesting considering that many trees growing in commercial orchards have been developed from cuttings taken from WWOG. The study found that some trees had been incorrectly identified and also that there appears to be considerable DNA variation within some of the trees previously identified as like-type cultivars. To fully understand the report we need to understand how the trees were ‘fingerprinted’. The DNA analysis procedure used in the study is called RAPD (Random Amplified Polymorphic DNA).

DNA terms explained (background info only)

Deoxyribonucleic acid (DNA) is a molecule that contains the instructions for the development and functioning of living organisms (animals, plants, bacteria etc). The DNA molecule is a sugar/ phosphate strand (backbone) that has atom groups called bases attached (see Figure 1). The order of the bases is the DNA code (Figure 1 and 2). Adenine (base) attracts Thymine (base) and Cytosine (base) attracts Guanine. In this way two DNA strands (the helix) are held together by molecular attraction.

A gene is a region of DNA that influences a particular characteristic in an organism. It contains the DNA code used to assemble proteins. Only about 1.5% of the human genome consists of protein-coding areas.

RAPD DNA testing (fingerprinting)

Related organisms have similar DNA. DNA testing determines relatedness by comparing segments of DNA. The RAPD method does not compare all of the organisms DNA. It does not compare genes. It only compares bits of DNA that might well not code for anything in particular (protein or otherwise).

What is compared?

The short segments (pieces or bits) of DNA that are compared are defined by two segments that contain specific codes within the DNA. It is not the codes that are compared but the distance between them and how many times they occur. The short specific DNA coded sequences define the beginning and the end of a segment that is compared. The amount (length) of DNA between the beginning (specific coded region) and end (specific coded region) varies from organism to organism. The number of times these codes occur in the DNA also varies organism to organism. The more often these specific coded areas occur the more segments there will be. Closely related organisms will have similar numbers of segments of identical length. Clones (identical organisms) have the same number of identical length segments.

How do we find these specific codes?

Small DNA molecules called primers locate the specific codes. Primers are designed to bind the specific coding regions. The primers act as a starting point and facilitate ‘*copying’ of DNA material.

How do we find out how many segments there are and how long they are?

To see the DNA segments with the naked eye you need an awful lot of it. To make a lot of DNA, the segments are ‘*copied’ many times. This is called amplification.
* Note: An exact ‘copy’ is not made but a ‘matching copy’. When the ‘copy’ is copied it will be the same as the first.

Equipment required to amplify the DNA segments?

The DNA amplification process is called a PCR (Polymerase Chain Reaction) and it is done in a PCR machine (Figure 3). The PCR machine is an automated cycler that can quickly heat and cool the reaction mixture. Each ‘cycle’ doubles the number of DNA segments in the mix. After the first cycle there are two copies of each segment. After the second cycle there are four copies of each segment and so on until after 30 cycles you have more than a billion. Each cycle involves three major steps that are repeated 30-40 times:

Step 1 The mixture is heated so that the DNA helix strands separate.

Step 2 Cooling allows the primer to bind single DNA strands.

Step 3 Warming encourages the enzyme (polymerase) to make DNA using a primer as a starting point.

Separation of segments and measurement

The amplified DNA is placed in a gel and an electrical charge applied. DNA contains many phosphorus atoms, which are negatively charged causing the DNA to be drawn through the gel by the current. Long pieces of DNA move more slowly than the shorter pieces. The DNA segments are inserted into the gel together (one lane per organism). As time passes the shorter strands separate from the longer strands (see Figure 4).

Setting up a lab

Thinking of setting up a lab in order to test your own trees? Table 1 contains the prices of some items you will probably require.

Can I have my olive tree DNA tested today?

It appears that olive DNA fingerprinting is not at this time available in Australia. Previously olive testing has been done at Wagga Wagga as per the ‘Olive Oil Yield, Quality and Cultivar Identification’ (OOYQCI) report (3) and at South Australia’s University of Adelaide’s Waite Agricultural Research Institute/ South Australian Research and Development Institute (SARDI). The good news is that Rod Mailer Principal Research Scientist DPI (Department of Primary Industries) Adjunct Associate Professor Charles Sturt University at Wagga is expecting to start another olive tree DNA testing project in the not too distant future (2007). Rod thinks they will be able to DNA fingerprint any olive tree for approximately $50 per tree and once they are “rolling” it should only take a couple of days to process the DNA and obtain a result (see footnote). As far as I’m aware ‘simple on-site’ DNA testing of olives and other fruit trees by an average gardener’ is not available yet. One day (who knows when or how) DNA field testing using a simple handheld machine will probably be possible. Don’t hold your breath.

Summary

The RAPD technique doesn’t provide information regarding the exact characteristic differences between the trees tested just whether there are differences. This is because only random areas of selected DNA are compared not actual genes. Those conducting the tests do need to have access to the ‘true variety’ ‘markers’ in terms of the lengths and number of different segments that will be amplified using specific primers. If you have two unknown plants and want to know if they are clones, no information is required. RAPD can do the job by comparing the segments amplified from the two DNA samples (eg. young leaves) you provide. Any organism (plant, animal etc) that has DNA can be tested using the RAPD technique.

Footnote

Just before this article went to print we contacted Rod Mailer. He provided us with Ref 4 and advised us that this year the ‘microsatelite’ technique would be used to fingerprint trees. It should be more useful than RAPD. The dendrogram (Fig 5 from Reference 4) is a fine example of how important and useful the research (Ref 3 and 4) has been in terms of olive cultivar identification and relatedness determination. Trees on the same branch are similar. You can see for example that all of the Sevillano trees are on the same branch. The closer the branch is to the right of the page the more related the two cultivars. Apparently other publications have not produced a dendrogram as successful as that in Fig 5.

References

1. http://www.dumru.mc.duke.edu/rapd.html
2. http://users.ugent.be/~avierstr/principles/pcr.html
3. https://rirdc.infoservices.com.au/items/01-023
4. Mailer, R.J. and May, C.E. 2002. Variability and interrelationships of olive trees and cultivars using RAPD analysis. Advances in Horticultural Sciences. (16)3-4: 192-197.

Bunya

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In South East Queensland, February to March is Bunya nut time, when the huge Bunya cones fall to the ground. If you can find a source of the nuts, you should try them. They are delicious if prepared well – try some of the recipes below!

Bunya Pine (Araucaria bidwillii) is not commonly used in edible landscaping in South East Queensland, but it should be! Not only is it a handsome tree, and a local species, but also the nuts are really tasty. Bunya pines are tall trees growing slowly to 40m, with a trunk that can be as big as 1.5m in diameter. They have distinctive prickly leaves and a straight trunk with interesting loose bark. It is preferable to plant several trees to ensure male and female flowers occur.

The female cone which contains the edible nuts is very large, up to 30 cm in length, and weighing as much as 5 kg. Each nut is contained in a tough scale, which separates from the cone when ripe. The nut itself is egg shaped, one end being pointy – rather like a giant pine nut.

Bunya is found mainly in the rainforests of southeastern Queensland and in northern NSW. It is prolific in the Bunya Mountains, but is also seen closer to Brisbane, for example around the slopes of the D’Aguilar ranges and Mt Coot-tha. It will grow outside its natural range, even as far north as Rockhampton. Bunya pine is also grown for timber.

Bunya pines are significant in the history and culture of Aboriginal people in SEQ. When the nuts were in season, there were numerous feasts and ceremonies involving many different groupings coming together. Many Aboriginal tribes travelled to the Bunya Mountains, where they owned particular Bunya trees and passed the rights to harvest down from father to son. They made notches in the trees to assist climbing up to harvest the cones. The nuts were used in many ways – raw, roasted, in soups or ground into a flour.

If you try the Bunya nut on its own, you may find it bland and a little dry, although it does a have subtle chestnutty flavour. The secret is to combine the starchy flesh of the nuts with other interesting flavours. A simple way to start is to boil the nuts for about half an hour (they open up like clams), shell them (this is a hard job that requires a sharp knife and care), slice and lightly fry the nut flesh in a mixture of curry and spices of your choice. These make great nibbles.

The boiled nuts can also be sliced or pureed and used in various desserts or savoury dishes. Grind up the boiled nuts in a food processor for a flour to add to bread recipes. A list of recipes for Bunya nuts can be found on the ABC radio’s web site at www.abc.net.au/recipes. Here’s one of our own recipes to try.

Process 100g boiled and shelled bunya nuts (see above), bunch of basil, or combined basil and rocket, juice of 1 large lemon, 50g grated parmesan cheese to a paste. Add olive oil, and salt to taste. Serve with pasta.

Fertiliser by Rainer Mache

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Lime: The softer and finer, the greater the efficiency

In farming, some terminology creates more confusion than clarity. In arable farming, the pH value is one of them. It is easy to determine but not always accurate and it says little about nutrient conditions in the soil.

According to Prof. Silvia Haneklaus at the Plant Nutrition Institute of the Federal Agricultural Research Station in Brunswick: “The pH value is not an overall indicator of lime requirement.”

The two most important minerals, calcium and magnesium, are not only exposed to competition through acidifying nitrogen ions but can be displaced by potassium, ammonium or sodium. The FAL scientist recommends paying attention to calcium saturation. Furthermore, the two principal lime elements, Ca and Mg, should be present in a certain ratio, ideally 72 to 19 percent in the soil solution. What determines the efficacy of lime fertilisation is not the level of alkaline components but the reactivity of the lime, says Dr Werner Köster, former head of the Agricultural Testing and Research Station in Hamelin. But even concerning the determination of reactivity there are differing views. From his experience it would be best to distinguish between immediate and long-term effects. Replacement of the calcium that has migrated downwards in the topsoil or the magnesium that has been withdrawn is the priority; any suggestions of a long-term effect extending over more than ten years make no economic sense.

German fertiliser legislation has set the bar for fertiliser limes very low, believes Thomas Huntgeburth of Kalkwerk Herbsleben. The origins of limes and their composition should always be taken into account. The properties of the two main elements differ. “Calcium has a lower electrical charge than magnesium and possesses a smaller hydrate shell and thus higher reactivity,” says Thomas Huntgeburth.

Dolomite limes are generally very hard, with low solubility and therefore less reactivity; above pH 5.8 they are not effective, in Dr Köster’s experience, which suits them at best only for fertilisation in acid soils. Softer limes are more reactive generally; the same goes for fineness. Harder limes should be more finely ground than softer ones. Fractions above 0.315 mm are basically insignificant in effect.

In Australia it is usual to pay only for the finer material. Another measure is the surface area; the larger this is, the higher the efficacy. Dolomites consist of smooth particles; soft chalk limes are distinguished by their large surface area. Farmers should also pay attention to precise distribution when spreading. Lime acts on the place where it falls. Two calculation models exist that draw conclusions from the sieve fraction on the release of the lime within the following three years.

One formula is used by the US consultant Neal Kinsey; the other was developed at the former Fertiliser Research Institute in Leipzig by Dr P. Runge, who calls it the neutralisation value. According to Dr Runge’s formula, chalk limes display a neutralisation value of 45 to 50 percent; Devonian limes achieve 30 percent and dolomites 28 percent. Liming is one of the most important fertilisation methods for yield; on top of this, it also helps to stem erosion and save water.

Liming must not, however, be viewed independently of the supply of other nutrients. In areas with animal husbandry on light soils there is a danger of excessive phosphorus supply causing calcium deficiency, Dr Köster stresses.

Too much potassium reduces magnesium and calcium uptake.

An excess of magnesium should likewise be avoided, since this provokes calcium deficiency.

Latin Names

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The 18^th Century saw the development of a system of scientific name classification for all living things by the Swedish naturalist, Linne, C. (1707-78) whose name is usually given the Latin form Linnaeus. He gave a name for each group (Genus) and within that group a name for each species; hence this is referred to a binomial system. This double name system works well as it is understood worldwide and avoids the frequently duplicated and confusing common names which not only have the same name for many different plants (eg. Christmas Bush) but also, in many cases, the multiple names given according to local dialects, areas and apparent relationship to other plants which bear no actual family relationship (eg. Blue Quandong, Blueberry Ash, Blueberry Fig as three of about eight common names for Elaeocarpis grandis which is not a quandong, Ash, Fig or related to any of those families).

The plant kingdom was divided into Angiosperms (all flowering plants) which were then subdivided eg. Monocotyledons and Dicotyledons

Monocotyledons have parallel venation in their leaves

Dicotyledons never have parallel venation in their leaves

Then families eg. Moraceae, Myrtaceae, Sapindaceae. All families have the ending ‘-aceae’. The last two letters ‘-ae’ are the Latin ending indicating the feminine plural form as well as the feminine singular possessive (= of_____).

Then Genus

which is masculine, usually ending in ‘-us’, eg. Ficus

or feminine with the ending ’-a’, eg. Acacia

or neuter gender with the ending ‘-um’ eg. Dendrobium respectively

(or in single form).

Then species

Which for the masculine, singular possessive form is eg. fraseri (=of Fraser)

’’ ’’ feminine ’’ ’’ ’’ ’’ victoriae(= of Victoria) and

’’ ’’ neuter ’’ ’’ ’’ ’’ beckleri(= of Beckler) or

’’ ’’ neuter ’’ ’’ ’’ ’’ fairfaxii(= of Fairfax). This form often came about in an attempt to form a Latin word from one which quite obviously is not of Latin origin. It was hypothesized that if Fairfax were to have been a Latin word its first person form (subject of a sentence) would have been Fairfaxinus or if an adjective to agree with Dendrobium then fairfaxium would be the appropriate form to agree with the neuter gender. In both cases (Fairfaxinus or fairfaxium), its was the singular possessive form which was required so Fairfaxii becomes correct!

The Linnaean system of classification required that all plants (and animals) have both genus and species as their identifying name; hence it is described as a binomial system. The species name usually refers to a particular feature of the plant, its natural location or is named in honour of a particular person or after the one who recorded it, some examples follow:

Backhousia citriodora where citriodora refers to the scent of citrus (citri = citrus, odora = scent). Lucky Mr. Backhouse had many sweet smelling plants named after him as he has a complete Genus bearing his name, but note that Backhouse has been converted to a Latin name with a singular, feminine ending and the species name agrees with it in both number and gender as both words end in ‘-a’.

Elaeocarpus eumundi being ‘of eumundi’. Strictly, one would expect that this should have been eumundis to agree with eleaocarpus or eumundii to properly indicate “of eumundi”, the area which comprises its natural habitat. (eumundi is of course an aboriginal word). Acacia victoriae understandably had the spelling of victoriae as the tree was named in honour of Queen Victoria. And not of the state of Victoria (as this plant is native to Queensland and the Northern Territory).I am indebted to Mr Paul Forster, of the Queensland Herbarium for research into the naming of citrus garrawary (including a 1912 American reference) as it is named after north Queensland botanist who collected many plant specimens for identification and recording. (The often seen but misspelt garrwayae is incorrect because it is NOT named after Mrs Garraway).

Now the examples are legion, where mistakes were made in having the Latin adjectival form, for species agree with the form for genus in both number (singular ands plural instead of both singular) and gender. Even so (there is good understanding around the world as to which plant is being referred to even if the Latin species ending is not technically correct. A good reference book by Debenham, C. The Language of Botany, Society for Growing Australian Plants, is one where the author has gone to considerable trouble to ensure that the correct Latin form is used in botanical examples.

Then there are many botanical names in Greek-derived Latin to further confuse and complicate the subject.

Now to a few notes on pronunciation. Many Latin words formed the basis for later words in French, Spanish , German and English. The Australian/English use of long syllable sounding diphthongs in words like bite and plate easily givers false impression as to the Latin pronunciation where most vowels were short. The current English word epicenter gives the same Latin short sound for the first two ‘e’ sounds and the ‘i’. The usual split of syllables required the following syllable to commence with a consonant and not a vowel. Thus ‘i’ as in ‘it’ or ‘bit’ and ‘Latin’ is pronounced ’la’- ‘tin’ and not ’lat’n as is usually heard. C was always hard like a ‘k’. So the pronunciation of ficus should be ‘fi’-‘kus’ with the short ‘i’ and ‘u’ sounds. Easy really, isn’t it?

Where there were adjoining consonants in each syllable, the pronunciation was base on simply splitting them, as this smoothed the flow of speech, and added colour and fluency to the classical poets’ works as they were read and spoken, e.g. in English, the word ‘planting’ would be pronounced in Latin as ‘plan’-‘ting’, but still pronounced as one word.

So an easy botanical example is eu-ca-lyp-tus.

Often longer vowels sounds were represented by two letters, e.g. ‘ae’ pronounced as if ‘ee’ as in ‘feet’. So now look at ‘pediatrician’ as an obvious English word of Latin origin and ponder the different pronunciation for ‘ia’ within the same word!

Pesticide free fruit fly control – is it possible?

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I was very interested at the last field trip to hear of Bruce’s success with fruit fly control. It set my mind wondering how a pesticide free trap might compare. As I am a Certified Organic grower I am unable (and unwilling) to use chemical pest controls. I have spent some time in the past trapping fruit fly but have never kept any records – there is plenty of anecdotal advice around on non-toxic options but no one seems to have documented any. As well as being interesting for my own use, I thought it might interest other members and inspire them to conduct their own research and report back, especially anyone able to compare chemical and non-chemical traps (which I am unable to do).

My traps consisted of two commercially available ‘baits’ and two home made ‘baits. Information given with the commercial baits is as follows –

Fruit fly lure – Yeast Autolysate. Used as an attractant with a compatible insecticide for the control of a range of fruit fly including Qld fruit fly and Mediterranean fruit fly. The attractant is mixed with an insecticide (chlorpyrifos, trichlorfon or maldison and applied as a coarse spray to the foliage of the trees. Highly attractive to female fruit flies. Suggested application – 20 ml in one litre of water, 50 ml per tree or 15 litres per hectare apply at 5-7 day intervals. Cost – about $12 per 250 ml. Supplier- Bugs for Bugs (07) 4165 4663 or your local produce store.

Wild May Fruit Fly Control System. Two products – Blue label eliminates the group of male fruit flies which include the Qld fruit fly and a number of species that attack stone and citrus fruits and a number of vegetable crops. Red label for the control of Papayan fruit fly and a number of species that attack fruit and vegetable. Suggested application 300ml per trap, two traps of appropriate attractant per acre. Cost – about $7.50 per litre. Supplier – Wild May Essential Oils Mt Gravatt (07) 3349 5283

My trapping experiment

Use a small (300 or 500 ml) soft drink container and drill (about 6 mm), cut or burn (with hot skewer) three holes about a quarter of the way down the bottle. Place approximately 50 ml of selected attractant in the container replace lid and hang in tree (mine were as shady as possible). The bottles used were clear except for one which was blue, this was included because Bruce reported Dr Dick Drew as saying the female fruit fly was attracted to blue – if this was so the blue bottles should contain more dead flies! These traps work by attracting the flies into the small holes. They cannot find their way back out again and therefore perish.

Yeast autolysate – about 5ml dissolved in water to make about 50 ml (about 50 traps for $12).

Wild May – about 50 ml of each of the attractants in separate bottle (about 20 traps for $7.50).

Urine – about 50 ml in bottle (very economical !).

Sugar, flour, banana skin – about one tsp sugar, one tsp flour, water to make a thin paste and about a quarter of a very ripe banana skin cut into centimetre squares (to get it into the bottle (also very cheap).

The number of flies in each trap were counted and results recorded as follows:

	DAYS 1-5	DAYS 5-10	TOTAL (10 days)
Red label	4	0	4
Blue label	6	5	11
Urine	0	1	1
Yeast (blue bottle)	19	44	63
Yeast (clear bottle)	30	48	78
Sugar, flour, banana	55	7	62

The results show that fruit fly trapping without poison is possible. My trials will continue and I encourage other people to undertake research and report back.

Compost Tea

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There are several forms of liquid fertilisers that most people are familiar with. The commonest are liquid fertilisers such as the commercial fish emulsions or soluble fertilisers. Alternatively, there are manure or compost ‘teas’ which are made from materials such as manure soaked in water. Herbal teas, such as those made from comfrey, are also useful for providing nutrients to plants. Most such liquids can be applied as a foliar spray or directly on the soil around plants.

Brewed compost tea, however, is completely different to these products. It is brewed aerobically, and this process grows millions of beneficial microorganisms to feed the soil and help combat disease. This type of compost tea is increasingly being used in permaculture and on organic farms as a way of improving soil fertility naturally to produce strong and vigorous disease-resistant plants. It is quite easy to make your own compost tea at home to try out its properties for yourself, and there are also commercial products available.

There are many articles and websites about making brewed compost tea. An article by Elaine R. Ingham, who is the president and director of research at Soil Foodweb, Inc. and a professor at Oregon State University in Corvallis claims that compost tea is more beneficial than simply applying compost to the soil in the traditional way. She states that compost tea “makes the benefits of compost go farther, helps suppress foliar diseases, increases the amount of nutrients available to the plant, and speeds the breakdown of toxins”.

There is sound science to support these claims. As Ingham points out, the soil is full of both ‘good’ and ‘bad’ microorganisms. The goal of gardeners is to enhance the beneficial microorganisms in this soil foodweb. The ‘bad’ bacterial decomposers and the plant-toxic products they make are enhanced by anaerobic, or reduced-oxygen, conditions. However, compost tea is made through an oxygenated and highly aerobic process, which grows the ‘good’ bacteria and other microorganisms. Good bacteria work against the detrimental ones in several ways: They consume the bad ones, compete for nutrients, and they compete for space.

The brewing process in compost tea production extracts microbes from compost and then multiplies them. Beneficial microorganisms include bacteria; fungi and protozoa. Ideally the compost tea will contain both a vast number, and a great diversity of types of organism.

Brewed compost tea can be used in two main ways. Used as a soil drench it provides food and energy for microbes in the soil. As a foliar spray it combat disease and acts as a natural fungicide – for example for controlling downy and powdery mildew on grapes. When sprayed on leaf surfaces, the beneficial organisms in the compost tea eat up the exudates from leaves that would otherwise feed harmful organisms.

Making your own compost tea

To make good compost tea, you need good quality compost which has been made aerobically. That means turning the compost heap and ensuring it heats adequately so weed seeds and pathogens are killed.

Ingham describes how compost can be dominated by either bacteria or by fungi. For compost tea to be used as a foliar spray, it must be bacteria-dominated, whatever the plant. Bacteria-dominated compost is also best for applying to the soil before growing vegetables and herbs. Research has shown that a foliar spray of bacteria-dominated compost tea is extremely useful to prevent the foliar diseases that plague most gardens. Therefore the bacteria-dominated compost tea is the most useful for home gardeners although fungi-dominated does have some applications.

Ingham’s main points for making good bacteria-dominated compost are summarised below:

compost should be made from a preponderance of green materials – a mix of 25 percent high-nitrogen ingredients, 45 percent green ingredients, and 30 percent woody material. High-nitrogen materials include manure and legumes, such as alfalfa, pea, clover, or bean plant residues. Green material includes any green plant debris and kitchen scraps. Woody material includes wood chips, sawdust, paper plates and towels, and shredded newspaper
mix a whole pile at a time
make sure you have a mass that measures at least one cubic metre.
Moisten the pile as you make it so that it is damp but not wet.
The more you turn the pile, the more the compost tends to become bacterial.
after six to eight weeks, the centre of the pile is cool or barely warm to the touch. The compost is now ready.

Brewing and using the tea

The requirements for making brewed compost tea are easily obtained. There are many different recipes for making the brew – Ingham’s simple method is summarised below, but you may want to research other possibilities on the Internet. You will need:

some of your well-prepared compost
clean water (rain water, bore water, or town water that has been left to stand in the sun for a day to lose its chlorine)
a 25 litre plastic bucket
an aquarium pump that can run three bubblers (air stones), three bubblers. and a three-way gang valve to distribute the air to the three bubblers
a couple of metres of tubing
unsulphured molasses (preferably organic)
something to use to strain the tea (e.g. old nylon stocking)

Tea made with this method brews for two or three days and must then be used immediately. So plan your batch to suit your needs, such as making it on a Wednesday for use on the weekend.

Method

Fill the empty bucket loosely half full of compost. Set up your pump and tubing so that the pump delivers air to the three bubblers at the bottom of the bucket. Hang the gang valve on the lip of the bucket and bury the bubblers at the bottom under the compost. Fill the bucket to within 7cm of the rim with water, and start the pump. When it’s going, add 30g of molasses, then stir vigorously. After stirring, you’ll need to check the bubblers to make sure they are on the bottom and well spaced apart. Stir the tea at least a few times a day. A vigorous mixing with the stick shakes more organisms loose and into the tea. Every time you stir, be sure to reposition the bubblers.

After three days, turn off the pump and remove the equipment. If you leave the tea aerating longer than three days, you must add more molasses or the good organisms will start going to sleep because they don’t have enough food to stay active. Let the brew sit until the compost is pretty much settled out, 10 to 20 minutes, then strain it into the other bucket or directly into your sprayer. You’ll have about 12 litres of tea. Use the tea immediately, within the hour if possible.

The solids can be put back into the compost pile or the garden soil, as there will still be good bacterial and fungal foods left in them.

Anaerobic decomposition

The most important thing in making brewed compost tea is for it to have sufficient oxygen, otherwise the tea will start to smell and become anaerobic, which can harm your plants. Ingham points out that “bad smells mean bad business”. Properly oxygenated compost and compost tea smells sweet and earthy. Anaerobic compost tea should not be used on your plants, as a product of anaerobic decomposition is alcohol, and even a very small amount destroys the plant’s cell walls. Ingham recommends that if compost tea smells bad, you can add another pump with more bubblers, and stir it more often, to aerate it until the smell goes away.

Using the tea

In a healthy your garden, spraying plants once in spring may be adequate . The beneficial insects in the garden should spread the compost tea organisms around the garden, preventing pest problems for the rest of the season. If you don’t have good levels of beneficial insects in your garden, you can spray at least once a month, or as often as every two weeks.

To control damping-off, spray the soil with full-strength tea as soon as you plant. On trees and shrubs, spray two weeks before bud break, then every 10 to 14 days.

References

‘Brewing Compost Tea: Tap your compost pile to make a potion that is both fertilizer and disease prevention’ by Elaine R. Ingham. From Kitchen Gardener issue 29, pp. 16-19

‘Notes on Compost Tea’ by Steve Diver, Appropriate Technology Transfer for Rural Areas, 2002. www.attra.ncat.org

Mangoes – Talk by Terry Campbell, DPI Bundaberg

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I am a little bit out of my depth tonight. Firstly I am not used to speaking to such a fantastic roll up of people so thank you all for coming out on a stormy night like this to talk mangoes. I normally now work in the post harvest system for mangoes and why they go green and not ripen properly sometimes, but I did spend 17 years in Mareeba, the home of tropical mango production in Queensland. I have spent 6 years in Bundaberg up until now, which is still home to some quite large mango plantations so I have a pretty big interest in mangoes.

Our contribution to being a member sometimes is to get up and speak about some topics that might be interesting to people. So I looked at a few of our training packages and tried to pull out all the things that were interesting at this time of the year in mangoes. I find this the most interesting part of your newsletter. If there is enough discussion we will all learn something about mangoes.

I recognize that mango growing in this area is one of the greater challenges in life. It is all because of what happens during flowering and fruit set. I think you will realize why it is so difficult to grow mangoes in SE Queensland after you hear some parts of my talk because the flowering is difficult, pollination and fruit set is quite difficult and maintaining disease and insect control at times in this environment is quite difficult – not impossible, so don’t give up!

We will go back to a little bit of science to explain that mangoes do follow that yearly pattern of vegetative growth after harvest, where we get 1 or 2 flushes. We also get a bit of a root flush. Then we move into some sort of vegetative dormancy and that might happen from about May onwards when we get set up for flowering. It is the environmental conditions that happen in winter – June and July that really determines what sort of level of flowering you get. After flowering it is the environmental conditions that we get in August-September-October that determines what sort of crop we get.

I reckon there are 5 IFs in mangoes:

IF they flower; IF they set; IF we get them through to maturity; IF they ripen; IF there is any money around on the market.

If those 5 IFs fall into place, it is a pretty profitable crop.

That is the basic phenological cycle that mangoes go through. As I hear people talk about manipulating flowering, they are doing it by trying to manipulate that phenological cycle: when the rest phase is and when the growth phase is. Here are a couple of facts: For mangoes to flower they have to have cold weather.
There is a way around it but it is quite difficult to manage but the traditional one is that you need cold weather to come in. 10 – 15°C to come in at the very early stage of flower development as long as those terminals are at least 7 weeks old. So we need dormant terminals that have built up carbohydrates, some cold and then action to happen, which is what induces flowering.

We can manipulate this in a couple of ways. We can manipulate dormancy like they do in the Philippines where they use Cultar® to actually put the tree into a false dormancy and then break dormancy with potassium or calcium nitrate sprays.

Sheryl: Can you go back a bit and discuss about the terminals being 7 weeks old?
Terry: That is the suggestion that the flush must be a hardened flush and building up carbohydrates otherwise it just doesn’t flower. We know young red flushes can flower and I have occasionally seen this in Mareeba, but a much better flowering occurs on buds dormant since end of May. We then need the cold as a trigger but not too cold or we get a male flowering.

Of course during fruit set it can also be too cold and if you start getting night-time temperatures below 13° during flower set you get quite poor set in Kensington Pride. 13°C is the benchmark figure but we know it is a little lower for R2E2. Calypso is certainly lower but for Kensington Pride we have a figure of 13°C that has worked out in the growth chambers. In Bundaberg up to 20th Sept we normally get overnight temperatures of 10, 11 or 12°C yet we can still set fruit, so when we get warm days, I think we get a bit of an offset from that. So now you can see that to get mangoes to work in an environment can be a bit tricky. You need cold weather to get initiation but not too cold. Then it has to warm up during flowering to actually get fruit set.

In some cultivars we can prune off early flowers to get re-flowering at a better time. In Nam Doc Mai which gets really bad powdery mildew, all the flowers can fall off but they will flower again. Some varieties are very good at re-flowering. Keitt mangoes are very good at re-flowering. Most of the Florida varieties are ok but Kensington Pride is pretty lousy. Ian Bally in Mareeba may have a list of cultivars which re-flower after flower pruning.

The other thing about flowering is the use of potassium nitrate to induce flowering. It only works on some varieties. It does not work at all on Kensington Pride. It works marginally on R2E2 but it works quite well on Carabao. The Filipinos and Thais use it twice to induce flowering each year. You have to have dormancy but calcium nitrate works just as well and is a little bit cheaper.

Watering

There is a lot of conflicting information about how you water mangoes during flowering particularly about putting the water off until fruit set. The water usage is quite low through winter but they do need to be kept actively “alive”, and need to be watered to push flowering at the right time. Start early September to get those buds going.

Fertiliser

It is very essential to fertilize mangoes to get regular cropping. You need to get new flushes every year to get flowering to get fruit set. Of course it is essential not to over-fertilize. As a guide I like leaves to 1.2% nitrogen coming into flowering. 1.2% nitrogen is certainly not dark green – you would have to say light green and when you go to the sunny side of the tree you think you have under fertilized it. It looks a little bit on the pale side. That is about 1.2%.

We know boron is important because of fruit set, and to get pollen tube growth you have to bring them [the trees] it at 50ppm leaf boron. Boron you can overdo it. Mangoes are very intolerant of too much boron but you have to have it. I am one of the people that advocates putting it on the ground because it is very important for sap flow and calcium nutrition in the tree. I notice your recommendations are giving boron sprays right through until October. Our recommendation is 0.9% soluble spray Solubor® at stage B because that will give us enough boron for what we do, but we should actually have it on the ground. Stage B is when the buds will be about 1-2cm long ie., early bud break. 1% is 10ml per litre. Some varieties like R2E2 need a lot of boron and if you don’t have enough boron you get the bent flower tip and you end up with some internal issues.

Sheryl: So you are saying spray the flowers with boron as well as putting a bit of boron on the ground.
Terry: Yes, in very low doses on the soil. 1gm per square metre. Mix with water and spray the ground. On our sandy soils we don’t exceed 10kg/hectacre treated area that is our top rate. Even at that rate in our R2E2 mangoes we get toxicity at times when the soil is not so deep. Boron deficiency symptoms are typically holes in the leaves and splits and trunk weeping.

Toxicity is indicated by a very irregular burn on the margin of older leaves.

Calcium If you don’t have enough calcium in Keitt mangoes you end up with internal troubles – what’s called Keitt Disorder. To overcome the problem we try to improve fruit load, lower nitrogen and increase calcium supply. You will see occasionally that 1 or 2 kg gypsum per tree is recommended and that is the ball-park, any more than that would saturate the soil with calcium. If your pH is below 5.5 use lime, and above use gypsum.

Sheryl: What size tree would that be in?
Terry: Probably a 3 metre tree.
Sheryl: You mentioned to stop jelly seed we need the calcium. Getting calcium into the tree is a bit difficult.
George: With calcium nitrate spray, does that actually burn the leaves?
Terry: We have to be very careful of the rates we use. I think 1% is fine but higher than that we start getting little bits of tip burn and if it is fruit that is getting a little bit of burn then that ruins the fruit. Depends on the pH, we mainly suggest using gypsum.
Sheryl: So how much per square metre?
Terry: The golden rule has always been about 10 tonne per treated hectare.
Sheryl: I think Peter says a closed handful.
Terry: That sounds a lot more sensible. I am saying that the commercial trees are using 2 kg on a 3m tree per year of gypsum.
Sheryl: What periods would you put them on? What growth of the tree?
Terry: It is very important to go for those major growth phases, it has to be on prior to flowering, again in November and then for the flush, but we do try to avoid the wet season particularly in the very sandy soils that we grow mangoes on you just can’t control and it all just goes through the system and you can’t control it.

Potassium and Magnesium They do like magnesium. When everything is set and we know we have a crop we can spend some money on the trees then we top up with potassium and magnesium but in a ratio of 2 to 1 potassium to magnesium. We tend not to put Potassium and Magnesium on until the fruit is about egg size. If you don’t have it you end up with a lot of internal troubles.

Diseases

The other thing that has to happen at flowering time is the control of diseases. This is to protect flowers and leaves. If anthracnose gets on older leaves it remains as inoculum for later on. Anthracnose is a problem in this area because we get rain at flowering and we have some inoculum in the tree and we get it spreading down to our flowers and young fruit and we get no fruit set.
With the way the disease spores infect the fruit we have to use a protectant fungicide like Mancozeb or a curative like Octave ®.

Sheryl: Octave is quite expensive isn’t it?
Terry: It is very expensive, but during flowering it is a best choice. If you are relying on protectants you need to ensure good coverage. So how do we control mango pests particularly without relying on inorganic chemicals? The first thing is never let a plant come onto your property that has diseases such as bacterial black spot. (Always known by the angular pattern that is slightly raised and slightly greasy appearance of the leaf spot on the leaf). It is such a difficult disease to try and cure – almost incurable on some varieties like Keitt. The next trick that we have in controlling diseases is controlling the inoculum level in the tree. We have been doing some work of actually going through and removing all dead material in mango trees. Now this can cost about $10 or $12 on a commercial orchard to get in, get material out and sweep it out from under the tree and get it broken down to mulch. But in some orchards it is the only way we have been able to control the disease, as whenever we get some dead material in a tree we end up with some quite nasty diseases like dendritic spot coming in on our fruit, so controlling the inoculum is really important. What does all this mean to those of you who have only a few trees? Well it means that before flowering, I like to have my trees really clean ie., when I go in and do that end of May prune to take the odd branch out and remove the dead wood.

George: Does the sunlight getting into the tree help?
Terry: It dries the tree out and lets a bit of wind go through it. If you actually target the dead branches, stuff that has been hit by scale that is good. The other thing is to have a uniform flush come away after, particularly to stay ahead of stem end rot. Do this in Feb.

Pruning

Give your Mangoes a light prune straight after harvest to get all of those dead sticks and any branches that have gone a bit vigorous. I try to get some shape back into the tree and get my flush coming away and then I come back about May-June to take out some more dead wood and some vertical branches that are giving me too much height. Leaves older than 2 years are actually parasitic on the tree which means they no longer contribute to the carbohydrates of the tree so all pruning should be designed to remove those leaves so leave new leaves on and strip all the old leaves off. Do this in May.

Pests

The other issue during flowering is the Flowering Caterpillar – not normally a problem but something we check for. We have some new chemicals which we use like Success [Yates® Success® Naturalyte® Insect Control] – active ingredient is Spinosad which is derived from naturally occurring beneficial soil bacteria and this is put on during early fruiting. If you are growing trees in mid-suburbia where everyone has lots of ornamental trees you would know about fruit spotting bug.

George: Especially in a garden with mixed fruit. They move from tree to tree.
Terry: They are very fast. There has been some work done in the Burdekin and Tablelands and we are finding the peak of the fruit spotting bug in September-October and it is causing fruit drop, but it is such a hard pest to control that we are hoping that we can wear this one. We haven’t found a pheromone for it that seems to work nor can we find lures to trap them and the only chemicals we have are harsh.

Our last pest that happens around flowering time is mango scale. Commercially it is our most severe pest. I think it is a problem because it causes dead material in the trees and just the very efficient nature of this pest. The females lay 200 eggs at a time and those little crawlers move out over the next 24 hours. They don’t move very far – they are all males. The females walk a bit further but the males stay close to their mother and in summer the life cycle can be only 40 days so it is a very efficient pest.

Member: Organic control?
Terry: With very good pruning and getting rid of the old material out of the tree and with some of these new parasites you will get away from this particular insect. We have imported a parasitic wasp and are doing trials before release.
Member: Possum control?
Terry: I have seen tin used successfully around the base to stop them climbing on the trees.
Sheryl: In a previous newsletter, in Mackay they had an old fishing net which they put at the base of the tree about 90cm high from the ground and about 4 layers. A possum likes something taut that he can hang onto so the net is loose and the possum does not like being off balance.

Varieties

Maybe it is more my taste but I actually prefer cultivars like Nam Doc Mai because I can get it to re-flower very nicely into warmer weather like October. As you will see in the latest newsletter it is explained that mangoes are one of those ones that are monoembryonic or polyembryonic. The monoembryonic ones we definitely graft because they do not come true to type from seed. The polyembryonic ones they do come true to type from seed but we also graft them because we have some data from Nth Qld looking at long-term yields and the actual grafted trees have always out yielded the non grafted trees even for things like Kensington Pride which are polyembryonic.

Dwarf Trees

I have had a little experience with the use of Sabre. I don’t know if Sabre itself is a dwarfing root stock or because on Sabre the tree is productive that it has kept the tree smaller. The only big root stock trial that has gone on in Australia is the one in Katherine and in that one Sabre came out pretty well. It has now been replicated by a grower up there who claims to have some very nice dwarfing root stocks but I have not actually seem them.

Sheryl: Is it a secret?
Terry: No, they are being commercialised.

Article compiled by Barbara O’Connor and edited by Sheryl Backhouse.