Talk by Peter Young from Birdwood Nursery – Qld Garden Expo July 2006

Zinc is one of the most important things for plants in regards to disease resistance as it is in humans and in fact nutrition in plants and humans is just about identical. We just get ours differently – we take it in by mouth and plants take it up through the roots and sometimes through their leaves.

Sooty Mould is growing on the excretion from insects so when you see it, it means that you have an insect problem so if you see ants, the ants actually drive away the beneficial insects that kill the bad insects which cause sooty mould so if you have sooty mould, it means you have an ant problem in your tree. Put a bit of Glad Wrap around the trunk, a bit of Vaseline on the Glad Wrap or you can buy Ant Stop which goes round the trunk of the tree which stops the ants marching up and down and you’ll get rid of your sooty mould problem. This can take a while to work so if you still have problems ie you don’t have the beneficial predators, you’ll have to try an oil spray. Bio-Oil or any of the summer oils and use it at the rate of 1:100 and it’s important to put them on during the life cycle – usually the 2ndor 3rd week in November. Oils suffocate insects and that’s how they kill them.  If you put the oil on the tree at the wrong time of the year, it will also kill the tree so don’t use any of the oils in winter – White Oil is the worst thing you can use because it takes a long time for the tree to recover from an oil spray. The other time to do it is at the end of February or March when the other scale insects release their young. Now this period is for the Sunshine Coast – if you live up north it would be earlier or down south it would be later.

In the old days your Mum use to use washing water over the trees when we used mild soap but the soaps these days I don’t know whether I would be game to throw them on your tree!

Rootstock  The big problem with Citrus is having the Citrus on the right rootstock. Trifoliata will give 100% disease resistance against soil borne diseases and collar rot and it gives the best quality fruit. The only time it doesn’t work is if you have very salty water. Flying Dragon is a dwarfing rootstock. Troyer rootstock we use for Oranges and is a cross between Trifoliata and Sweet Orange. Bush Lemon rootstock  If you buy a tree on Rough Lemon or Citronella rootstock, it dies of disease. If you put a Lemon on Troyer, it’ll live 6-8 years – they’re not compatible. The only rootstock that Lemons are compatible with is Meyer on Trifoliata and Eureka on Benton. We guarantee our trees. When you’re on the wrong rootstock, you have all these deficiency problems because the rootstock can’t function properly supplying the top with the right nutrients so the whole key is to have the right rootstock. It use to be compulsory to have the name of the rootstock on the label, but in NSW they’ve just removed this but all our labels have this. We do about 120,000 citrus a year. Fertilise in June, August and November. 1kg of Dynamic Lifter per sq. mtr. Which gives the tree most of its trace elements that it requires then a closed handful of a mixed fertiliser eg Crop King 55 or 77 or 88 or Nitrophoska Blue.

Sour Fruit  Another question I get asked is about a good sweet Mandarin and all of a sudden the fruit have gone sour. This is Cleopatra rootstock. It’s used for the western areas where drought is a problem because this rootstock is highly drought tolerant. It won’t like the wet soil on the coast but it’s still used by a lot of nurseries which supply the western region and often in NSW so if you buy a tree, it could have this rootstock.

Figs  The time to prune is end of July and cut it at a comfortable chain saw height so what we’re trying to do is to get 2-3metres of growth each year and you’ll get figs all the way up the new growth. If you don’t prune the tree, it will lose its vigour and you’ll get short scrappy growth and small scrappy figs! They’re rampant feeders and very susceptible to nematodes so they love to be mulched with organic mulches. You can use Dynamic Lifter or any chicken manure 1-3kg per Most of the cow/horse manure improve the soil pH so long as you don’t overdo it – no more than 20litres per of any organic manure. Mulch only once a year in the dry season – here it’s July/August but generally we usually mulch in spring on the east coast of Australia. Normally our wet season is Jan/Feb/March so we want our mulch to be broken down before the wet season comes. Fertilize every 4-6 weeks during the growing season. The best fertiliser in the business is Nitrophoska Blue – a German fertiliser – and every little pill has the fertiliser in each pill. It’s now made by Incitec in Brisbane under licence in Australia. When we buy other types of fertiliser eg Crop King 55, 77, 88 etc. we get a mixture of all the different crystals together and they separate out so when you get to the bottom of the bag, often you end up with all these fines and the course material comes to the surface so you get more variation in your nutrients. Osmocotes and Nutricotes are too expensive to use in your garden.

Mulch  I’ve got this thing about people taking their garden clippings to the dump because you don’t need to because you’re taking away all your nutrients. Buy a chipper/mulcher for around $200.00 and put all your small branches/leaves then return everything to the garden. If you have anything that’s too big, then put it under the mulch. Woody chips are very good at controlling disease in the garden because the cellulous in the hard heavy timber actually antagonises things like die-back disease eg Phytophora or pythiems then when we bash it up we destroy that celluous so a lot of farmers are putting it back under the tree whole without bashing them up – they take longer to break down of course and don’t look as nice so you hide it under the smaller branchy leafy mulch and the longer they take to break down, that’s good and you’ll find that the tree roots come up into those big heavy limbs – even Avocadoes.  Most plants love cannibalising their own vegetative material because that’s what they do in nature.

If you wanted to break it down quicker and make your own compost, you have to put nitrogen into it because the little bacteria break down the organic matter and 1 bite of nitrogen to 28 bites of organic matter so when they chew up all the nitrogen that’s in the dynamic lifter or whatever you put in, then the process stops – everything gets cold and it just sits there even if you turn it over nothing will happen so if you throw a bit of Urea or Sulphate of Ammonia, you’ll get the process starting again.

Fertilising Avocadoes  A young tree treat them like citrus. If it’s 3 years old, you wait until the fruit size is as big as your thumb and around Christmas or a bit after. Normally the secret with avocadoes is to keep the compost heap under the tree – no more than 15cm deep but avocadoes are a true rainforest tree and their feeder roots come up out of the ground and feed in the surface mulch so if you don’t want the tree to drop its fruit, then you must keep that surface mulch reasonably moist. In their native country, they have summer rainfall so if the tree stresses, it’ll start sucking water out of its fruit during the day and pump it back in at night and you’ll see these little ring necks forming on the neck of the fruit and they fall off and that’s stress so although they need to be well drained, they don’t like a lot of stress.

Fertilising Stonefruit  Normally we give them just a little bit at pruning time which should have happened in early winter – a closed handful of a mixed fertiliser just after. Calibrate your hand. Put a set of scales outside and put in 10 handfuls – shift your decimal point and it will tell you how many grams your hand is. When I was in the DPI I use to get farmers to do this. Some farmers had 300gms so if you told them to put on a handful per, they’d kill their trees so it’s really important to calibrate your hand. Fertilise again when the fruit are half grown and then you do it again just before harvest to help the tree fill out its buds for next year’s fruiting. It’s really important just before Christmas to chop the tree off at nose height. The reason is that you want the fruiting wood to develop below that point so it’s easy to look after and easy to harvest. If you let the tree keep on going, the framework of the tree will get out of reach and you don’t want all your fruit up high anyway.

Boron Calcium & Gypsum If you give fruit trees in general too much Boron, they go yellow and they’re very sensitive to excessive boron as are citrus. The boron in Dynamic Lifter is enough to supply a citrus tree if you use it 1kg per sq mtr for a Custard Apple tree. When you get into Avocadoes and Mangoes they need 4-5 times more than what’s in Dynamic Lifter. Calcium goes hand in hand with Boron. Gypsum supplies Calcium – it doesn’t alter your soil pH but we should be putting on at least 100gms of Gypsum per sq. mtr per year or on anything we want to fruit well. You can also do it on your Grevilleas and Banksias. Calcium is a major nutrient in our bodies and in plants as well. All the Citrus have higher calcium than Apples and apple growers are fanatical about putting Calcium on so we have to be the same with Citrus. Citrus get a dimple on the end if there’s a Calcium deficiency – it’s a rotting of the blossom end. Limes suffer from it very badly so it can be a Calcium breakdown. Capsicums and Tomatoes get a big black spot on the end. Put it on right now in winter as it takes 2-4 months to get into the tree’s root’s system. If we put on Dolomite or Lime, it takes 2-5 years!

Pruning Avocadoes are no different to any other tree. Always carry a pair of secateurs on you when you’re out in the garden. There’s a balance between top and bottom with all trees. Every time you chop a branch off, a root dies back. If you burn a root in the ground, some leaves will die back. If you want to keep your trees small, when the tree gets well established – about 5 months to get established – you can nip and tuck small amounts whenever you like so if you do that all the way through a trees life, you can keep a tree any height you want so a Hass avocado that might grow 20 mtrs tall, you can keep it down to 2-3 mtrs tall. The general rule is straight after harvest, if you want to do any major pruning, then that’s the time to do it but you don’t do it a little bit all over because that reduces your flower and fruit set for next year, you take out one or two big limbs and no more than 20% of the tree at any one time so just before flowering you can take out 1 or 2 big limbs. After 5 years, 5 x 20% equals 100% the tree is gone so it recycles itself and that pruning tip is very important. That goes for Grevillea/Hibiscus etc. this tip will keep the tree young forever.

Mangoes   Getting them to set fruit every year is a major problem because once they’ve had a dry period ie when you’re not watering or no rain and we then get a bit of rain, they’ll flower. They’ve all flowered too early this year on the Sunshine Coast. Because it’s happened very early, they’ll reflower again and the 2nd flowering should set a crop. You can stimulate the tree to reflower in 4-6 weeks if you remove the old flowers that haven’t set. 10° for one hour on one night will completely kill every ovary in the flower. They’ll still set fruit and you’ll get pollination, the pollen tube goes down and sticks his nose into the ovary – same as in humans – the ovary is dead and the little fruit thinks it’s pollinated but because you haven’t had fertilisation, the little fruit  split and fall off so you get pollination without fertilisation. Brazil and South Africa have similar problems. If they still reflower when it’s still too cold, you can snap off the flowers over a period of time so reflowering happens over a period of time so you should get something to flower when the temperature is right. The commercial farmers all over the world particularly Israel will remove all the flowers off the lower part of the tree, then they’ll come back and do the section in the middle, then the last bit at the top so that way a 1/3 of the tree will set a crop depending on the variety. Some varieties are quite cold tolerant but unfortunately they are not available to the home gardeners. They’re tied up by big corporations.

Pruning  Light tip prune after you harvest the fruit. You can also do limb removal at this time. If you have a 100 year tree and you want to bring it down to size, the 2nd week in October is the time to chop it off. Paint the butt with white plastic paint and it will then regrow.  When it gets to a metre, tip prune so you then have a small tree again.

Stone Fruit  Don’t prune out all the pussy wood on the inside because they fruit on their spurs. They always fruit on the previous summer’s growth. Prune 2nd week in Oct. which is just before the fruit fly become active.

Native Bees  They do a very good job in pollinating but they don’t do well with some of the bigger flowers eg. passionfruit but they do well on citrus but it depends on the flower makeup. The Israelis have been over here taking all our native ozzie bees back because our native bees will work at temperatures when European bees won’t get out of bed!

pH  What’s important with your fish pond, pool or your own blood is your pH. If the pH is wrong in your soil, then it can’t use the fertiliser you put on so go to a Produce Agency and buying an Inoculo test kit and you get around 4,000 tests out of one test kit so share it with your neighbours so your pH should be 5.8 – 6.8pH. Most of our soils around here get down to 4-5 which is really acid so we need to put dolomite which has magnesium and calcium or lime on which you scratch into the surface. The probes you can buy to test with are only good for use in water but they’re no good for soil. Check your water pH as well.

Possums   They’re not bad to eat but I can’t eat a whole one!! Farmers are having the same problems with wallabies so you’re better off to train the ones you’ve got and they’ll keep all the others away. You can use an electric fence. Dogs will also keep them away but they’ll bark and keep you awake!

Fruit Fly  The best idea is to have an enclosed area and Netpro have a net which keeps out your mites and thrips complete. If you decide to put a net over your fruit trees and peg it down to the ground, you’ll most likely have fruit fly because they’ll still be hatching out of the soil from the previous summer so it’s important to understand the life cycle of your pests. Fruit Fly is a native pest to Qld. and the rainforest need it for survival. It’s always been here and it’s never been any worse then it was before. It use to only go down to Coffs Harbour but now that we’re growing fruit all the way down the coast, fruit fly is now down into Victoria and because they’re Qld Fruit Fly they’ve developed a cold tolerance and they’re now surviving in he south. The male and female hatch out of the ground in the spring, they hibernate in winter then mate in spring and 80% of the female fly migrates within a 40km radius of where they were born. 99% usually die out around Warwick/Gayndah and every year they get reinfected from Brisbane back yards. You’re best to just wrap a whole branch rather than the whole tree. The female lays her eggs under the skin of developing fruit and she puts in with the eggs a little bit of yeast. The fruit fly maggots can’t eat fresh fruit; they have to feed on fruit that’s breaking down so the grubs hatch out and start eating the rotten fruit. The life cycle is so quick in summer – 1 or 2 days for the eggs to hatch; 3/5/7 days depending on how hot it is for the maggots to fully develop; they crawl out of the fruit and drop onto the ground, burrow in the ground and 10 days later out emerge the adults and then the whole process starts again. So, the only way is exclusion unless you want to spray and there’s no reason to spray for fruit fly.  Palmwoods Farm and Garden Company at Palmwoods are the Australian importers of fruit fly bags and you bag each fruit and it works a treat and you can reuse them. They’re made in Japan and they have all different sizes. Fruit Fly traps usually only attract the male and there are now some that will attract both the male and female but they never get them all. When you use lures eg autolysate you’ll find it will attract all the fruit fly from your neighbourhood into your garden so if you start, you generally have to keep it going. You can spray with insecticide but best not to. The bags will also keep out the fruit piercing moth. In Feb/Mar/April the citrus will be attacked by this moth. You can also use other types of bags by just clipping the corner off to let out condensation but don’t use plastic because fruit fly will lay their eggs straight through plastic. It has to be paper.


Article collated by Sheryl Backhouse


Authored by: 
Peter Young
Sourced from: 
STFC Newsletter October - November 2006
Date sourced: 
October 2006