Talk by Don Gordon

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I started off in Nambour in the DPI for seven years and then spent another 30 odd years around Caboolture. I was the banana inspector for the northern suburbs of Brisbane an  I roamed around Arana Hills, Everton Hills and Grovely because that was the last lot of the bunchy top that was around Brisbane.

I have always had my farm and grown mainly avocados and custard apples, and then messed around with a few other things. You go along to someone who has a crop and you think: wow, this is the way to go. So the next thing is, a dozen plants go in and then after 5 years they get ripped out because of  climatic or a number of other different reasons.

I tried grapefruit and ended up with Tangelos. Tangelos you can sell. Grapefruit: you can go to a big fruit barn and they will take a box a week. So if you have 20 or 30 boxes at a time, you are going to have to find 20-30 fruit shops. I tried the Brisbane markets.

One day I went up to Nambour DPI and someone said “Your Avos in Sydney are $22-25 a carton”; I was getting $10 in Brisbane and I never even knew they were being sent to Sydney, so that is the marketing situation.

Deciding what to grow, I now would always be fairly sceptical about newspaper articles, journals and the like. These are very often created by people who have a different motive at the time and they are also in a different environment. I tried Loquats grafted onto Quince A because in Israel they have Loquats grafted onto Quince A and get 60 tonne to the acre or hectare. I got these Quince A plants and grafted them on, they grew so slowly and after several years I chopped them out. Seeing someone growing the crop is probably one of the main things that you can work on with the oddball crops anyway.

Climacteric and non-climacteric fruit. Climateric fruit are fruit like Papaw and Rockmelon. They need to be on the plant for a certain length of time before they are actually able to be eaten.

Non-climateric fruit like Carambola or Banana can be harvested over a greater range of time. They don’t have to be completely filled out to mature themselves once they have been picked. When you get onto this phenology stuff it applies to animals as well as plants, and it is an interaction of plants and animals with the environment, the climatic conditions, the day length variation throughout the year etc.

It has been found that  when you talk about branched plants like tomatoes or trees, density or row placing is not that critical. You have to have access to harvest. You have to have irrigation systems laid out so that they distribute the water evenly, and maybe there would be some cases where you could have a crop that was hard to spray because there were too many trees there. But generally the whole system, with density in branched plants, is fairly forgiving.

Fertiliser on the other hand is a different thing. The wrong timing, particularly of nitrogen, can cause a lot of things to go vegetative, shed flowers, drop fruit. The rate that you use of the chemical is fairly important. When you get over to the single stemmed types like Papaw, Corn, Bananas, Pineapples, fertilising is not so critical. I saw a banana grower once who by mistake put 15 bags of urea on 2 acres of bananas over a 4 month period and the bananas were just about as green as the rest of the bananas on the property. The fruit was the same quality as the rest of the bananas so it is not that critical, but the row spacing in the single stemmed plants is more critical. You can end up with a concentrated harvest of smaller fruit under high density, where you might desire lower density to have bigger fruit that you can pick over a longer period of time. In the case of the Pineapple they jam them in, they get a certain sized pineapple which suits a certain sized can and it suits the pineapple industry quite well. So that is your phenology.

With bananas, you must get plants from a recognized source with a permit from the DPI [now DAFF]. There is not much bunchy top in the area here, but the DPI while responding to possible reports on disease occurrence have dropped out on the amount of surveillance they are doing on the stuff because it is already here in the country. So they are mainly worried about what turns up from time to time, and resources get pushed into these things. 
I started in 1969, and as far as incursions and interstate movement everything up until 1990 was a dream. You would ring up an old bloke in Head Office twice a year, now there are people in every area. To send stuff to WA there is a great heap of protocols, inspections that have to go on because of melon thrips, silver leaf white fly and things like the absence of soil in potting mix. So there is very little bunchy top in the area, but if people pick up their plants and cart them a few kilometres away, as well as being illegal, it would place more work for the authorities in the future and a burden for the industry, as bunchy top travels from backyards to commercial farms. Diseased plants form a nucleus start up in the area, so one day an inspector goes down a road, that house has got it, that house has got it, that house has got it, and eventually it peters out after you have been around the block a million times, been into places. Being the government (representative) you couldn’t just go in there with 2-4-D and just spray all over the place, you had to make contact with the owner. When you went to a place like Buderim, the owner was invariably in Sydney or Melbourne. The people next door never even knew who they were, so you would have to go through a whole lot of messing around with real estate agents ,and then someone would say “go in there and hose the place down with 2-4-D if you need to”, right so in you would go.

The ring spot in Papaws is spread out in a fair part of Brisbane. It spreads more or less the same way as bunchy top does in bananas except it is a lot faster. You will find a 10 acre patch of Papaws, if it gets a few ring spot there is probably another 100. If you had half a dozen ring spot in 3000 Papaw plants there is probably another 100 that have it that are not showing symptoms, and then in late spring you get a bit of rain, a bit of warm weather, and it just flushes away and you get a variegated sort of foliage on top. The shape of the Papaw leaf is the same as it is when it is green, but you have light and dark areas of yellow and green through it, and it makes it look a bit variegated. It is a pretty looking plant until you realise it has ring spot. Also there are dark streaks in the petioles and eventually irregular ring-like spots on the fruit. Ring Spot is spread all through Brisbane in bits and pieces. We never had any regulatory powers to tell people to wipe them out or give them an order, except that you can’t take Papaw plants out of the Brisbane area, whether healthy or diseased, but when you told people about it or left a note in their letterbox and you went back, they usually chopped them all out. There are usually 1 or 2 little ones there, but the poor little things they might have a chance, so they leave them there because they might grow out of it, but of course they won’t. That is just human nature, as well as the general lack of knowledge of disease movement by the general public.

Since I have retired, which is nearly 2 years ago, I have always wanted to do something with ‘run to waste hydroponics’, using tyres up 1mtr high, with 14 litre pots tied into the top tyre, filled with furnace ash growing tomatoes. They weren’t too bad; determinate type tomatoes, so they just hang down over thetyres, slots in the tyres to stop water getting (and) staying in there – that was last summer. This summer it has been Eggplant, Lettuce, Pepinos and Cucumbers and they have all done well. It works quite ok and is running on tank water. I might learn more about conditioning the water the hard way if I started using the dam water, but I have plenty of tank water just for 50 plants. I like the idea because it largely looks after itself.

The previous Christmas I went to the daughter down in Sydney, and I told the guy next door the minimum to run the hydroponics which was fine. This year I went to Perth to visit my other daughter, the guy next door was away and I gave the lady over the road the run down and she sounded interested. The plants survived. In this editing of the talk, what I was trying to say is that plants in this type of culture are a little more forgiving than the novice would believe. For example, last year the tomatoes went for a half day or so without water. When I saw the problem I thought blossom end rot for sure, well they were fine. It is not until you grow things in this way that you start to consider that the basis of all life could come down to no more than a dozen or so chemicals.

I grow avo’s, custards, tangelos, papaws. I have a few bananas. I am trying to process a few lightly roasted macadamias with just a thin layer of chocolate on them. I have a few acres of rubbishy country that I have filled up with bana grass (pennisetum purpureum) that was planted before Christmas and it is 2mtr high now. The plan is to scoop it up with the tractor and spread it around the avo’s. With avocados you need the antagonistic organisms (fungi/bacteria), use manure, straw calcium sulphate (gypsum) built up to antagonise the phytophthora. You can spray phosphorous acid on, you can use your fertiliser right, you can irrigate properly, but the root rot is nibbling away 24 hours a day, 7 days a week. It increases the cost of growing avo’s when you have to maintain this sort of stuff. They are not so good when the root rot gets going. Being a natural rainforest tree in its native situation it does not have protection against sunburn, so when you lose 50% of the leaves from root rot the sun comes in and burns the branches and that is the big problem there. As well the avo’ tends to ration out its photosynthates to favour fruit development first, and then vegetative growth second, and then what comes a poor third are the roots. So you can get a great looking plant with a great crop on it, but if you don’t keep pushing everything into it, like water and fertilizer. In 12 months time it can still have another crop on it with a few yellow leaves, and looking pretty crook, so that is the problem with avo’s. They will overbear themselves out of existence.

The hydroponics are in three rows: the first row is all Pepinos, then I have the other two rows of Pepinos. But in the pot you can have a Pepino in the middle, and while the Pepino is slowly growing you can put a cucumber or a couple of cucumbers, or maybe a tomato, or even a lettuce and it matures, and then the Pepino is up and going.  What I have yet to find out is whether the old plants can hang on well in hydroponics. If they don’t want to hang on, if I have to keep on layering them into the associated pots to keep younger stock all the time, they might get the chop. To propagate them, put a little marcott on the Pepino just with grass, you don’t have to cut around it or anything. Shove the grass around it, put a bit of old plastic bag around it, tie it on and 2 weeks all the roots are in there. Cut it off and stick it in the pot; so they are easy to do a marcott on and you can do a plant that has 30 or 40 leaves. Of course if you want to go for mist you can take cuttings and put it in mist. Even in hydroponics I have just stuck a piece of a branch in the hydroponics with all this heat and the thing grows. The system gets a half a litre of water 5 times a day on each plant in summer.

Member: Any problem with fruit fly in Pepinos?
Don: They absolutely go mad over them. You have to treat. They seem to get in fairly early in the fruit when you don’t really think they are there. Pepinos are a climacteric type fruit. You could not grow them and treat them like tomatoes. With tomatoes you can harvest the fruit when they are not really ripe, not showing much colour, and they will still turn out sort of all right, whereas they are best if they are left on the plant until they are fully ripe. But Pepinos need to be on the plant until they are fully ripe, so that is one big problem with Pepinos.

Member: Tell us something about the tyres?
Don: That gives you the height above the ground. People will tell you if you are going to put this in commercially you are going to need heaps of tyres and one day the disposal cost could be high. With slots in the tyres so they drain I have not found any problem with mosquitoes breeding in them. If you don’t put the slots in them they tend to tip over, they fill up with water when it rains and they fall over. There is a stake in between each two tyres and that is a cost.

Sheryl: There is some literature to say that we should not use tyres to grow plants in, but you are just using them as a prop so your plants growing in pots inside the tyres can hang down, and the plant doesn’t touch the ground.
Don: Yes, you could say that. Slow breakdown rate as far as I am concerned. I use tyres for my irrigation sprinklers. I have a couple of tyres high, I put a little cross in the top of the tyre and a little slot in the bottom of the tyre, and I put my sprinkler there. Sprinklers are 0.5 mtr high above the ground so they can be located when they get covered by weeds. When you create the right conditions to grow a crop like avo’s you are also creating the right conditions for  weeds, and it is your tropical legumes like Glycine, it is the main one, and also Green Panic. These things just grow. I can slash and a week later it is a foot high in summer, and so very often I will start my slashing when the weeds are like that in between the trees, but around the trees I will have that down with a smaller mower, sprays etc.

Member: Can animals be used within crops?
Don: When you start with animals everything is fine until you start spraying the crop, then you have a different taste there and they start experimenting. Then you have the problem too of the residues of the chemicals that the animals could be feeding on so that is a problem. You can use sheep or goats to do a lot of damage to the weeds, and when they start to chew the bark get them out, but then there are the sprinklers and they get caught up in the pipes etc.

Member: Can you tell us more about the Ring Spot in Papaws?
Don: Ring Spot on Papaws is a virus and it is in the plant, and the only way is to chop them out, but like bunchy top in bananas once you destroy that plant you don’t need to burn it or take it away. Once that plant has wilted the aphids can’t feed on that plant, and so chop the plant up and leave it in your garden. Then in three months time stick another papaw plant in and you will not have ring spot. The only way that you will have ring spot is if those aphids were able to go and feed on some other Papaw somewhere, and then come back onto your Papaw.

George: How is bunchy top spread?
Don: Bunchy top is spread either by people moving planting material that is infected with bunchy top, or via the banana aphid. The banana aphid has to feed for a certain amount of time on an infected plant and then it is able to infect another plant for several hours. If that aphid goes and feeds on a lantana plant, or a thistle, or a grass, it loses the virus. It can’t maintain the virus in its system. If it has living young, which aphids do, some aphids are able to transfer the disease to their living young, and I think the cucurbit viruses in watermelon and zucchinis can be shifted that way, but the banana one I don’t think it can be. The mechanism that the aphid has to spread bunchy top is not an efficient method of distributing the virus. That said, if you have a backyard down in a gully and no one knows it is there, and because of the terrain you can have difficulty detecting the disease, when driving around. Southern Queensland has hot spots of bunchy top – Mapleton, Montville, Palmwoods, Woombye. When you get into the city or town, then you have a bit more access when driving around but it was always a problem. Sometimes a farmer would get one bunchy top every year and he would chop it out and that would be the end of it. He would recognize it early, but the problem commercially with bunchy top is what is called “symptomless” carriers. You have a banana plant infected with bunchy top but it won’t show symptoms for at least several months. So aphids are feeding on it, going around the local vicinity infecting other plants and then one day, it gets recognized and chopped out, but that plant has been infecting for a long time. That is the biggest problem, that is why one farmer will get one or two every few years and he will see it quickly and chop it out. Another grower might end up getting rid of considerable areas, because a patch might be so thinned out to become uneconomical. Bunchy top in otherwise healthy plants exhibits itself well, while plants with nematodes, or drought stressed, are harder to see the symptoms. We in the industry talk about “old men”. They are bunchy top plants that have had it for a long time. The centre leaf basically in a bunchy top plant is shorter and not as wide as the previous one. The banana plant throws over 40 leaves from the time it comes out of the ground, to the time it gets a bunch. The first 30 to 35 of them are visibly longer and wider, once they get to about 35 leaves if you suddenly start to see that the leaves are shorter and not as wide as previous leaves, then there is something wrong and that could be bunchy top.

The real determination of bunchy top are the lines which are like morse code when you look in the younger leaves from underneath. You might have to hold the leaf up to the light and you can see these definite lines. Once you have seen it once you will know it, and you will know it from then on. Bunchy top affects Lady Finger, Cavendish, Gold Finger, the whole lot.

Member: What is Panama Disease in bananas?
Don: Panama – there are several races or strains of panama disease in bananas. It is a fungus. It is in the soil, if it is there. Lady Fingers are the most susceptible although there are a few other types that are grown experimentally which are more susceptible. Cavendish are less susceptible and Gold Fingers are less susceptible again. You are not supposed to have Cavendish in the backyard, so if you had Panama disease and Lady Fingers the next alternative is Gold Finger, and of course Gold Finger produces an enormous bunch. If it is over fertilised, especially in summer or you try to ripen it too quickly, the fruit has a short shelf life. Managed right it is a good banana.

Member: What type of soil is suitable for Avocados?
Don: If you have a soil that is droughty, that wets up fairly quickly when it rains, and it dries out quickly after rain, that is not very good. If it is a heavier soil that does not warm up like a light soil does, so its temperature is more uniform throughout the year that is better.

If the soil is naturally high in calcium and organic matter and has a good moisture retention then that is a plus. Deep, well drained soil is not prone to water-logging.

The other thing is that avo’s do not have root hairs. The plants that have the greatest number of root hairs are probably the grasses. I read once where a grass had a total length of all the root hairs, even though they were only about 2 or 3mm long, can be so many thousands of miles just in one plant. All the little root hairs keep on growing out and then dying all the time, but they give the plant a great surface area to take moisture in, but avos do not have root hairs. The finest roots are about 2mm wide and no root hairs, so once you drop your moisture in the soil down to 10% below field capacity the plant temporarily shuts down. Field capacity of water – the soil has been saturated and when it has been drained out what is left is the water holding onto the particles of soil, and that is called field capacity and it varies with different soils. It is lower in a sandy soil and higher in a heavy soil. But a heavy soil will have plants wilting when the water is at a higher level than in sandy soil, so in some ways a sandy soil can feed water into a plant when there is not very much water left in the soil.

Member: Is there a symbiotic organism like a mycorrhiza for avo’s?
Don: Under laboratory conditions there are some mycorrhizas that colonise the roots of Avocados. Research in the future to establish a symbiotic relationship, be it with a mycorrhiza or some other organism — in the field, that has significant benefit to the crop, appears to be on the move by the looks in California and Israel. Certainly it would be an interesting field to work in. The future could see work on it in this country if plant pathologists are able to get the funding for this research. Macadamias have a mycorrhiza. There are other mycorrhizas that are adaptable to a wide range of plants, and they are sort of beneficial to all of them, but there are some plants that have a specific mycorrhiza for that plant. 
Member: Where would mycorrhizas be obtained?
Don: To get a mycorrhiza of a specific type for a specific thing you would have to talk to a laboratory and someone who is likely to propagate that thing and distribute it out to you. Another suggestion would be a specialist in the particular crop.
Member: How do macadamias get mycorrhiza?
Don: That was the old thing with the macadamia nursery. The macadamia nurseryman, if he propagated his macadamias in pots, before sale he would collect some soil from the orchard and put some on the top of each pot, and that would inoculate them with the mycorrhiza.

Member: Are there suitable ground covers for macadamias?
Don: The sweet smother grass sounds as though it is going to be used a bit more in macadamias for under the tree. Macadamia growers tend to have a problem by removing the leaves so they can harvest, so they don’t have the organic carbon going back into the soil so much, and this may be one of the reasons why they often have macadamia decline after a number of years.

Member: What affect does Banana Weevil Borer have on bananas?
Don: Banana beetle or banana weevil borer, tends to affect a plant that is unthrifty to begin with – more prone in the Cavendish types. You can treat for the problem by spraying around the base of the plant. A lot of it is sanitation by getting rid of the old plants. The beetle borer became resistant to dieldrin then gradually they became resistant to other chemicals. A chemical will come out and it will do a good job for a few years, and then a grower will say “I never had control”.  The only chemical that you could get for beetle borer for bananas in the backyard would be Lorsban [now a group 1B Insecticide, and too hazardous for use by householders – website.ed.] but it costs about $50.00. Your best strategy for beetle control is just practice general sanitation, water and fertilise reasonably well you can get away with a lot. I have not treated my bananas with anything for beetle for about 10 years and they still produce reasonably well. The lady fingers are more tolerant of that type of thing. Nematodes are very often the culprit because they weaken the plant, and the beetle tends to get in more where you have a weaker plant. A starved plant is more likely to have problems like beetle.

Member: Have you found any residue in bananas in Australia with these things?
Don: When the banana plants are sprayed around the base with chemicals to control beetle borer there has been no evidence that the material has got up into the fruit. Even in the days of dieldrin, when people used dieldrin around the base of plants the only way problems occurred was when the fruit was sprayed illegally.

Member: How can macadamia nut borer be controlled?
Don: There are a number of chemicals that can be used for the macadamia nut borer. If you have a macadamia variety that has hardened the nuts by Christmas, it is usually tough enough that it is not really all that prone to the problem. If you have a variety that is susceptible you would have to monitor the activity of the pest and do a treatment, and it would be easy to control I guess compared to other things.
Member: What are the predators for the borer?
Don: They are actually a little wasp and the eggs come on a card and then you staple it onto the leaves and the eggs hatch out and they parasitise the nut borer. Member: How would these insects be kept?
Don: If there are hosts for them they would become naturalized in the area. Member: Would they be successful? Don: It depends what you are going to spray. You would have to buy them in at the same time every year. I know one grower that has been buying them in for lychees, but I am not sure what he has been doing for the other problems that you would get in lychees.

Member: What problem is the Fruit Spotting Bug?
Don: The fruit spotting bug is a fair problem in avo’s and custards, to a lesser extent in macadamias. There are two species. Both species affect avo’s, one species affects custards. Chemical control is virtually the only way especially in the early part of the season when the fruit is soft. The harder varieties like Hass and Sharwil are less prone once you go past Christmas. I have Fuerte, Hass,Sharwil and Reed and I drive along and come to a Fuerte tree and I go for good coverage, but the Hass and Sharwil I fly past them. I will still do both sides of the tree. Whereas custards this year I have not seen much bug in them at all so I have been going a bit lighter on them for better or worse.

Member: How does the DPI monitor chemical use?
Don: They do residue tests. When I first started in the DPI a visit to the Brisbane markets would see cabbages coming in that were reeking with dieldrin, and no one had any powers to do anything about it at all. But if they were rotten or had grub damaged they could be condemned. Well now cabbages or anything can come into the markets riddled with grubs, that is quality control, let the buyer beware. But if someone in chemical services of the DPI goes to a market, usually from some kind of an idea that a district might be using more of a chemical that is normally used on, say orchids, and there is only about half an acre of orchids in the area but there are 1,000 acres of another crop in the area, they will say “what is going on?”. They might go and sample something from the markets, or shops, or from the farm, and analyse the produce for that chemical. It is not the way to run a business by using chemicals that are not registered for the particular crop. Sometimes a chemical might be only registered for a certain stage of a crop, like only on the non-fruiting ones not on fruiting ones. Following the directions on the label is the best port of call.

Member: How does Anthracnose occur in mangoes?
Don: Anthracnose happens when you have cold and wet conditions. You can go to the Philippines or New Guinea where the temperature is never below 25 and it rains all the time and they eat mangoes six months of the year, but you can go to a place like Bowen where they get a few cold times every now and then, and a little bit of rain. If they do not spray they will lose a certain amount of their crop. Down here you are in that situation where the cold and the wet is coupled with little eco systems around south Queensland. There are some little eco systems that are a little bit colder and a little bit damper, and not enough air flow to dry the plants out quickly, and they are very prone to anthracnose.

I have 15 mango trees. I have rarely got anything from them because I never ever sprayed them, so rather than knock them down and put them over to tangelos, I am thinking I have left them there for 10 years, or so maybe I should do some spraying, so that is what the plan is next spring. Then you have the protective chemicals like the Mancozeb which you can put on and it is cheap. You put on Copper, but when you see rain go over to the eradicating type chemical (Octave), which costs a lot more to use but you should not put it on too much, because you can get resistance to the chemical.

Member: How might future incursions of pests and disease be handled?
Don: The DPI do random checks of the markets in relation to that sort of thing. There is a certain amount of surveillance going on too. After all this stuff like the fire ants there has been an increased amount of traps put down near the airport and the port for a lot of forestry pests.So the idea would be if we get something like the gypsy moth in, we would end up with earlier notification of it being there because the fire ants were just there a little bit too long. They were there for at least 5 years and probably every month was costing an extra couple of million dollars while they were just growing and moving around the place. So there is a certain amount of plant health people who are going into corners of Queensland and making themselves known, recording what is growing, doing a GPS of it, and then that would go up to Cairns and it is all on a database there. Because you have the mango problems up north, the weevil and two species of leaf hoppers; one is in Mareeba now. Because they treat for fruit fly the fruit are ok to move to markets around the country, but anyone with a nursery in Mareeba can’t send mango plants out of the Mareeba area.

I grow these bush-type snake bean. I tried to get the ordinary old running snake bean. I searched all around the place and I could not get any. I went to the place at Burpengary that has a little market (CREEC), and went there and I got  these. Some of these have been left too long on the plant. They are better when they are a bit smaller. It is a bush and produces a lot then it starts to run a little bit. I have two plants in every pot in the hydroponics and probably not too bad as a thing to grow. I also have a cucumber which I have found down in the Redlands area and I gave the seed to a farmer. He grew it and then when I started on the hydroponics I wanted the seed, so I got the seed back from him. Now there are a few people growing it around the place and I think it is related to the German cucumber or Italian cucumber. It tends to go a bit yellow when it gets a bit older. This is one of the problems. There are a lot of nice things around that are good to eat that last well, but because they go a bit yellow that does not mean that they are going to go rotten; but in the eyes of the consumer they are going to go rotten. The customers might not buy them in the supermarkets once they go yellow. That is the sort of problems in horticulture. There are a few things around that are nice things to have but they need a special kind of management. Gold Finger banana is one, they do not have a big idiot factor attached to them as regards ripening. If you throw in Gold Fingers into a room that has Lady Fingers, the Lady Fingers have a greater respiration rate. They will up the temperature of the Gold Fingers when they are only just starting to ripen. Then they tend to ripen too quick and then don’t have a shelf life.

Don: The snake bean seed pods I have kept for seed – the pods are as thick as your little finger and you have to let them really mature to use them as seed. Once the green colour has gone but the pod is still fleshy the seeds can be removed. To store them a fungicide like copper would be worthwhile.

Sheryl: Banana bags – I can’t get any more of these.
Don: In the backyard if you get a hessian spud bag it is open at this end here, cut it along the bottom and then half way up the end. Then you get a two pronged gadget on a pole and you put it up, and then hang this part here over the bunch coming down. It will tend to hang there for quite a reasonable amount of time. If you get a storm it might get blown off and then you can hook the thing back up again. That works quite well with Lady Fingers.

George: What does a banana bag do? It obviously keeps pests off but what are the other things?
Don: If you see a banana plant that has a half filled bunch and it has got that light amount of yellow to it. That is a sunburn condition which is going to affect the quality eventually. That is one of the main reasons why they use them. The other thing is that it is a stable temperature in the bunch cover. It does make a bit of a difference but it is not the be all and end all in summer time. In the backyard you will still get reasonable bananas without putting any bags on at all. Commercially it is going to give you a better quality product so that is why they put the covers on.

I have heard that a flying fox is able to detect a ripe fruit as it flies over the top of things. They can be flying over a banana patch, and if there is one ripe fruit in a patch they will go down to that one. You can have the flying foxes starving out in the Melaleuca forest and they will eat green peaches, but they will only pay slight attention to the bananas, and a commercial banana grower knows that once a flying fox attacks one fruit it will come back to that one bunch night after night. So he will just leave that bunch there and let them clean it up. They are not really that much of a problem in bananas like they are in other crops, even lychees down here. But lychees up in North Queensland they are a much bigger problem. The lorikeets are the king of the lychee attackers.

Member: What do you know about grafting Eggplant on to Devils Fig?
Don: I used the Devil’s Fig and grafted the eggplant onto it and they went for two years. You are doing it to control bacterial wilt. If you grow the eggplant in soil without plastic mulch, and use overhead irrigation your soil temperature remains lower, and you do not really have bacterial wilt. Same as in tomatoes. Fruit is always a little scarce in the wild I feel because of fruit spotting bug, because you will go to a plant and you will hardly see any fruit on it. Every now and then I would come across a plant that has two or three kilos of fruit on it, so I would bring them home. If you get the fruit and put it in a paper bag and stick it in the house, the whole house has a beautiful spicy aroma about it when the fruit dries out. Of course the Thais and Indonesians use the Devil’s Fig fruit in curries. The giant Devil’s Fig has slightly more lobing in the leaf and brown hairs up towards the top of the plant. I have never used it. There are more thorns on it, sharp little spikes. So I have just stuck with the ordinary Devil’s Fig which looks more like an eggplant plant. If you took the thorns away from it you would not be able to tell the difference much between it and the eggplant plant. However the eggfruit plant has purple flowers while both figs have white flowers with green berries that go yellow on ripening, similar to the wild tobacco plant.

Member: Would the Devils Fig have any potential for skin cancer treatment?
Don: I don’t believe that the Devil’s Fig has got anything like that going for it. The one that had potential was the other solanaceous plant, Apple of Sodom. Devil’s Apple, not Fig, and Apple of Sodom, are very low shrubs with very crinkly leaves and a lot of spikes on them. Devil’s apple turns out to be a one inch diameter cherry tomato look alike, but Apple of Sodom is a green fruit of the same size,with stripes on it which goes yellow when it is ripe, and it is very high in alkaloids and it is poisonous. There was a company from overseas and they wanted someone to grow Apple of Sodom. The DPI looked around and said we have plenty of Apple of Sodom, go to any dairy farm and walk along the fence line and you will find it growing around the place. They analysed the stuff, then they decided there was another kind of solanaceous plant that grew in Ecuador that had more of the alkaloids, and of course the labour costs there would be less, and they grew that for the skin cancer treatment.

Member: How would we be sure we had the right one?
Don: The ordinary Devil’s Fig has dark purple in the stem and is more adaptable. You will go around farms and you will see it around creek banks, and you will see an odd plant here or there. The giant Devil’s fig with the brown hairs up towards the top and the extra lobing in the leaves you will find it in the swamps and you will find it up on the hills in the heavy soils. It is not so much adaptable as the ordinary Devil’s Fig. Maybe the giant Devil’s Fig would be all right. I have seen backyards in Brisbane where people have grafted the giant one and they seem to be having success with it. Sometimes both species live together.
Member: Is there anyone in the club who might have seed of these?
Don: Peter at Beerburrum has the ordinary Devil’s fig.

Member: What happens when a tree falls over?
Don: A plant has something called apical dominance, and where you have a tree that is naturally symmetrical if it falls over or half falls over, it will start to grow back to its original symmetrical shape. One of the problems of avo’s and custards is that they have a different sort of an apical dominance. You will get a bud on a branch which will dominate other buds, you will end up with a vigorous shoot growing, and an avo’ tree  can have a branch 6 inches round, going out several metres to the side. When I slash my big avo’s and custards you just don’t drive past a tree, you reverse the tractor back and forwards underneath the tree and it can take 5 minutes just to slash under one tree. If a tree gets damaged in some way, it will eventually try to build itself back to its original shape. The thing to remember is that any branch that is exposed to the sun between 11 – 3pm, if it is perpendicular to the afternoon sun as in the case of avos and some others, they sunburn. A better idea would be to paint the thing with a plastic type paint, or I have used Sunstop, which the pineapple growers spray on. I have used a mixture of Sunstop and casein from milk. White plastic paint, Bondcrete is another one, anything that will stay on for a while that is going to reflect the heat. Oil based paints would have a worse affect than the sunburn so they would be a disaster.

George: You are actually talking major damage when you are saying sunburn. You are talking about the bark dying back to the wood.
Don: Yes, in the case of an avo’ it can actually creep into a branch, so you have physical damage there. It has gone right in to the branch and one day you come along with the chainsaw to cut it off, and what it looks like in cross section is a horse-shoe. That is how susceptible avos are to sunburn. Citrus probably not as bad. Custards will still get burnt. I have two rows of custard apples and on Australia Day 2004 one whole row was blown over and there were ten plants in the row. Two of them were blown over and broken over. T he others just got blown over. So I just trimmed them all up and they have been just fine continuing on growing. In their case I just let the legume grow here and there on the stem. They are not as high as they used to be but they still produce.

Member: What is the technique to prune Avo’s?
Don: You tend to want to take the top off the tree. You have branches going vertically, they command more sap flow than the ones that are horizontal. If an avocado gets a crop on it, the crop weighs it down and so it is not that bad. When I harvest, if I see a shoot coming that is half inch or 1 inch in diameter and a metre long and it is at the extent of my gear that I use for picking, I know that if I don’t cut if off it is going to be 3 m long in a years time. It will have a whole heap of fruit on it then and I can’t get to it so I will chop it off. You hope you are trying to push more growth out sideways that is going to be easier to pick. They are quite a prolific thing and do not have too many problems or weak crotches like other trees do. They do not have the tensile strength of a custard apple. A custard apple is like a jungle gym. When the kids were young they would be up the top of the tree and they would be hanging from the branches and throwing the fruit to you. Whereas with the avo’ if you stand on a branch, it does not have the give. A custard apple 1 inch diameter it will support your weight to a certain extent because half the time it is sitting on another branch anyway. You can crawl around it without any problems but an avo’ is a different structure and a different strength of wood. You can’t really climb around in an avo’ without damaging it a fair bit.

Member: What about other parts of the tree?
Don: Do a minimum of trimming. You can trim underneath the tree because you do not want the fruit hanging down on the ground, but what happens with an avo’ when it gets 3m or 4m high, about 7-8 years old and you think you will knock all these bottom branches off, you are actually knocking off about 1/3 of your bearing capacity. I used to get offcuts from the sawmill. I will use them to stake the branch to keep the branch above the ground – just cut a V notch in them. When the tree gets bigger, the branch looses its vigour and you tend to cut them off but propping is a worthwhile thing.
George: In the backyard you want a smaller tree, you don’t mind losing a few fruit. As I understand it, with Mangoes, Avocados and Lychees, if you prune to size after they finish fruiting, as long as they can get a bit of growth to get some new shoots you will still get crops next year. Is that right? 
Don: That is a reasonable way to look at it.

George: We have an Edranol avocado which seems to stay reasonably small on our block and it produces every year. What about other varieties?
Don: Reed is not a bad avo’ for the backyard. Reed tends to be mor an upright tree than other varieties. The fruit are round like the old seedling types.  Sharwil is a good variety as far as a mid season goes, not so prone to anthracnose, fairly resistant to bug once it gets a bit of size about it. Fuerte and Wurtz are thin skinned varieties and are susceptible to bug and anthracnose. It seems that all the quality problems seem to creep in when your tree is unthrifty. If your tree is growing well you don’t seem to have so many problems with the quality of the fruit. 
George: With avocados it is well worth growing from grafted trees. Seedlings will occasionally never set fruit, sometimes they will take 20 years. We have one that has actually produced after 5-6 years. There are problems with seedlings. The grafted ones are a bit expensive that is the problem.
Don: Avo’s and Custards are the easiest to graft. The ones with hard wood like Lychee and Macadamia are the hardest.