Growing avocados: common questions
Growing avocados: common questionsSimon Newett et al., DPI&F
John Dirou et al., NSW DPI - Agriculture; Greg Moulds, Victoria; and Alec McCarthy, Agriculture WA
This information has been extracted from the Agrilink Avocado Information Kit, which provides information on all aspects of growing and marketing avocado in Australia.
This section contains the most commonly asked questions about growing avocado. The answers are as brief as possible. Where this is difficult and more detail is required, we refer you to other sections of the Agrilink Avocado Information Kit.
Economics
A lot of avocado trees have been planted recently. What are my prospects for making a living from avocados?
Over-production is always a potential risk in an unregulated commodity market and increased production from new orchards has resulted in a substantial reduction in prices. However, we believe that reasonable returns can still be made where growers strive to produce quality fruit with good flavour, little or no skin damage and relatively free of pests and diseases. This requires skilful management of all orchard operations as well as harvesting and postharvest handling.
Success also now depends on gearing production to the needs of the market, with the fruit being produced and marketed under some form of quality management. It is also increasingly difficult for small growers to profitably compete in the market and we recommend that they consider joining a cooperative or marketing group. New growers may also take some years to attain the skills required for profitable production.
How much fruit will avocado trees produce?
Avocado trees that are allowed to grow to full size without light and space restrictions can yield up to 500 kg of fruit per tree per year. However, in a commercial orchard where trees need to be maintained at a manageable size for ease of spraying and harvesting, yields are significantly less. For example, at a commonly-used commercial orchard spacing of 8 m x 4 m (312 trees/ha), eight to ten-year-old trees should yield about 50 kg of fruit per tree (about eight trays). This will vary, depending on variety, district, season and the level of management. However, from maturity onwards, it can be difficult to maintain consistently high yields because a biennial bearing pattern tends to develop with a higher yield year followed by a lower yield year (an 'on-year'-'off-year' pattern). Canopy management practices also determine the sustainability of yields.
What sort of income can I expect from avocados?
We estimate that income after variable costs are deducted will range from about $800/ha when trees first start bearing to about $5000 to $8000/ha in the tenth year. This assumes a yield of about 12 t/ha and an average price throughout the season of about $12.50 per tray. However, when fixed and overhead costs are also considered, the average net return at maturity ranges from about $1000 to $3000/ha.
Land
Is my farm suitable for avocados?
Farm suitability is determined mainly by the depth of well-drained soil. Depending on rainfall, you need 1 to 2 m of well-drained topsoil before you reach any impervious clay or rock layers. Check soil depth with a backhoe, auger or posthole digger.
Another important requirement is suitable temperatures during flower development and at flowering. During the six-week flower development period from budbreak to the point of flowering, night temperatures should not exceed 15°C (5 to 10°C preferred). Day temperatures should not exceed 25°C (20°C preferred). During flowering itself (generally around September), night temperatures should not fall below 10°C, particularly for temperature-sensitive varieties such as Shepard and Sharwil.
Other preferred characteristics are flat ground or gentle slopes (up to 15%), good wind protection, freedom from frosts and a good supply of high quality water (ranging from 4 megalitres per hectare in wetter areas of Queensland up to 18 ML/ha in some of the drier regions of Western Australia).
Should I plant my trees on mounds?
Soil depth requiremetnts for avocado vary depending upon rainfall. In areas with over 700 mm of rain per year, you need well-drained soils with no clay layers or rock shelves within 1.5 m of the surface. In lower rainfall areas, 1 m of well-drained soil is generally sufficient. In high rainfall areas (over about 1500 mm per year), at least 2 m of well-drained soil is recommended. If you have marginally less than the depth of well-drained topsoil prescribed for your rainfall then mounds can improve drainage. In high rainfall areas, mounds are also useful as part of the surface water management system. However, as mounds can also create problems, we recommend that you seek professional advice from before proceeding.
Varieties
Which varieties are best to plant?
The varieties you plant depend on the location of your farm. Hass has the highest market acceptance and is a reliable producer in most areas. We suggest it should make up the bulk of the planting, except in warmer areas where small fruit size can be a problem. In these warmer areas such as the Mareeba-Dimbulah Irrigation Area and the Bundaberg region, Shepard is suggested as the major variety because of its early market advantage. Other varieties may be grown to supply niche market opportunities. Be guided by your marketers and seek a range of other opinions before deciding.
What can you tell me about the variety Gwen?
Gwen has the advantages of being a late maturing variety and a small, semi-dwarf tree. However, it is prone to biennial bearing (good production in one season followed by poor production in the next) and is relatively unknown on the market. At this stage, it is suggested for trial planting only in colder areas such as Sunraysia-Riverland and around Perth. The variety is protected by Plant Breeders Rights (PBR) and can only be grown under licence.
What can you tell me about the variety Lamb Hass?
Lamb Hass is a new variety that has not yet been properly tested in Australia. In evaluations overseas, it tends to mature later than Hass and has a more upright and compact growth habit. It crops heavily and is prone to biennial bearing. The fruit appears similar to Hass but on average is larger. The variety is protected by Plant Breeders Rights (PBR) and can only be grown under licence.
Can I grow Shepard in south-east Queensland?
Under most circumstances, Shepard will crop irregularly in south-east Queensland because of cooler temperatures during flowering in late winter and early spring. Consequently, it is not recommended for commercial production. It is best suited to areas with mild winter temperatures such as the Mareeba-Dimbulah Irrigation Area and the Bundaberg district. It is not suitable for the cooler areas of the Atherton Tableland, south from about Walkamin.
Do I need to mix varieties?
Varieties do not need to be mixed at planting, at least in sub-tropical eastern Australia. In most production areas of eastern Australia, pollination and fruit set are adequate in single variety blocks of trees. However, in colder areas such as Sunraysia-Riverland and the south-west of Western Australia, some mixing of varieties may be beneficial for improving pollination and fruit set. Seek specialist advice before proceeding. Also remember that the introduction of bee hives at the correct stage of flowering may be as important in improving yields as the mixing of varieties.
Planting and establishment
What spacing should I use to plant my orchard?
Tree spacing depends on whether you opt for high, medium or low density plantings. High density plantings (say 8 m by 4 m) give the best returns, but cost more to set up. Because these plantings crowd together much sooner, the tree canopies must be hedged or trees removed when crowding occurs. Low density plantings (say 12 m by 10 m) provide lower early returns per unit area but save the cost of tree removal in later years. However, larger trees increase picking costs, reduce picker safety, and have lower fruit production and quality. Medium density spacings (say 9 m by 6 m) are a compromise.
Where can I buy trees?
We recommend that you buy trees from one of the ANVAS (Avocado Nursery Voluntary Accreditation Scheme) accredited nurseries. These trees are grown under special nursery conditions to ensure they are free from root rot and other diseases. Indexed trees free from sunblotch viroid disease are also available on request. If you are considering exporting fruit, some countries will only permit the import of fruit harvested from indexed trees.
When is the best time to plant trees?
Where frosts occur, we recommend September-October. Otherwise, April-May is best.
Should I put fertiliser or manure into the hole when I'm planting?
In general, no, because you can burn the tender feeder roots of the young tree. If you want to put fertiliser or manure into the planting site, do it one to two months before planting so that it is well broken down by planting time. In less fertile soils such as those around Perth, soil analysis results may suggest the addition of phosphorus and selected trace elements just before planting. This is acceptable, as these fertilisers pose less risk to tree roots but in no circumstances should nitrogen, potassium or animal manures be added to the soil at this stage.
Things that go wrong
My trees look sick and yellow. They won't grow and fruit is small and of poor quality. What's the problem?
Your trees probably have root rot disease. Check the photos of root rot in the Problem Solver section of the information kit and compare them with your symptoms. If your trees are located on light sandy soils, also check your irrigation schedule, as water stress can sometimes produce similar symptoms to root rot disease.
During December, January and February the fruit drops off my trees. Is this normal or can I do something about it?
This is generally a normal fruit drop. If you have a heavy fruit set, then you'll have a heavy fruit drop. If you have a light fruit set, you'll have a light fruit drop. The only way to minimise fruit drop is to water the trees well from flowering onwards, particularly around the Christmas-New Year period. In hot dry areas such as Perth, the use of irrigation 'pulses' during the day is believed to reduce the risk of natural fruit drop from water stress.
Sometimes small fruit drop after damage from fruitspotting bug. This dropped fruit will have a dark sunken spot on one side.
Why do some of my trees flower well, but not set fruit?
The most likely explanation is that the variety is reacting to cool temperatures. The cool temperatures have two effects. If day/night temperatures are less than 18°/10°C during flowering, only male flowers develop. If night temperatures fall below 10°C within three days of pollination, then most fruitlets will abort. Some varieties such as Sharwil and Shepard are particularly susceptible to cool temperatures during flowering. Another possibility is boron deficiency, as boron is very important in pollination. Also check that bees or other pollinating insects are present and active.
The leaves on my trees (especially Wurtz and Hass) have turned a bronze colour. What's the problem?
Bronzing of leaves sounds like tea red spider mite. If you inspect the upper leaf surface carefully using a hand lens or magnifying glass, you may see small, maroon-coloured, spider-like creatures crawling around. These are the mites. You may also see the white cast-off skins of the mites as they moult.
My trees are flowering at the wrong time of the year. Why are they doing this and will I get any fruit?
Trees flower at the wrong time of the year because a cool period is followed by warm weather. The trees think they have gone through winter and are coming back into another spring, so they start to flower again. Generally fruit does not set from these flowers. If it does, it is often rounder than normal and poorly developed. For this reason, it is best discarded. If fruit is retained, it will have to be treated differently because it will grow and mature at a different time of year to the regular crop. Remember that trees will generally flower again at the normal time.
Why do some of my trees yield well, but others do not?
The most likely explanation is there is significant variability in your rootstocks. There is nothing that can be done in the existing orchard. However, for future plantings, first do some research to ascertain the most appropriate rootstocks for your farm. Then insist that the nursery supplying your trees uses seed from a recognised, good-performing rootstock type and, where possible, that the seed comes from the same maternal source. Another option is to use clonally propagated trees. These cost more, but will produce a more uniform orchard.
I've got holes or cracks with white powder around them on my fruit. What causes this?
This damage is most likely caused by fruitspotting bug, though Queensland fruit fly and fruitborer cause similar damage. The white powder is a dried sugary exudate that bleeds from the fruit in response to bug feeding. The exudate can also be seen on twigs and the trunk when damaged by phosphonate fungicide injection or boron deficiency. Because your response will vary according to which insect is responsible, correct diagnosis is very important. Carefully examine the internal symptoms of damage using the diagnostic pictures in the Problem Solver section of the information kit.
If growers in Western Australia see this type of damage, contact Agriculture Western Australia immediately as these pests are not yet present in that state.
I never see fruitspotting bugs on my trees, but I keep getting damaged fruit. Why?
Fruitspotting bug is a very shy insect that will move away and hide as you approach. If you are getting continuous fresh damage, you must spray the trees regularly from fruit set until mid-April, whether you see the bugs or not. Some orchards, particularly those close to rainforest, are more susceptible to attack and require more attention.
My Hass fruit is turning black on the tree. What should I do?
Fruit can turn black for two reasons. It may have been hanging on the tree for too long and is beginning to colour up naturally. Or mature fruit can turn black in the spring from moisture stress caused by hot, dry weather. In both cases, fruit quality will be reduced, so affected fruit should not be marketed.
An exception is in the colder regions of south-west Western Australia. Here, fruit will begin to purple before harvesting is completed. This is normal for late-hanging fruit in these regions, but growers still need to closely monitor internal fruit quality to ensure fruit is not left hanging beyond acceptable limits.
Root rot disease
How do I know if I have root rot in my trees?
The best way to determine if trees have root rot is to scrape away the mulch layer under the trees and examine the feeder roots. Root rot shows up as black roots. Check the picture of root rot in the Problem Solver section of the information kit. If you are in doubt, submit a sample of roots and soil for pathological examination. This is best done in spring and summer when the soil is warmer and the trees are growing more actively.
What should I do to protect newly planted trees from root rot?
The best way to ensure the trees are healthy is by buying only ANVAS accredited trees. Then apply metalaxyl granules around the tree straight after planting. Repeat this six to eight weeks later. Also avoid planting new trees in areas where you have previously had major root rot problems, or on slopes below existing orchards. If the new trees are being planted in a new block of land, try to isolate it from existing blocks and disinfect machinery before it is brought into the new block.
Do I need to treat healthy trees for root rot every year?
Yes. We recommend that even apparently healthy trees be injected with phosphonate fungicide at least once a year in early summer to keep them healthy. Alternatively, apply six foliar sprays of phosphonate fungicide between spring and autumn. Trees with mild to severe symptoms should be injected twice a year. Foliar sprays are also recommended for trees with a small trunk diameter (less than 4 cm), where trunk injection is impractical.
When should I inject my trees?
Timing of injection depends on how severely trees are affected by root rot. If trees have no visible symptoms, inject once in early summer, six weeks after the end of the spring leaf flush. It trees have any visible symptoms (yellowing, droopy leaves, leaf drop), inject twice a year. The timing of these two injections depends on the severity of root rot symptoms. For trees with mild to moderate symptoms, inject as soon as most of the spring flush has matured (late November in south-east Queensland), and again in mid-March. For trees with severe root rot symptoms, inject at the start of spring and then again in mid-March.
Should I plug the injection holes after I have injected the phosphonate fungicide?
No. We recommend leaving the holes as they are and allowing them to callus over. However, if high pressure injection devices are being used, holes may need plugging after the injector has been removed to prevent leakage of fungicide from the hole.
Can I spray the phosphonate fungicide on the ground to control root rot?
No, because phosphonate fungicide breaks down very quickly in the soil and consequently doesn't work well. It is also likely to encourage the development of strains of the Phytophthora fungus that are resistant to phosphonate fungicide. The fungicide works best when it is applied to the leaves or injected directly into the sap.
Can I spray phosphonate fungicide on my trees rather than injecting?
Yes, but sprays of phosphonate fungicide should only be applied to apparently healthy trees. Don't use foliar sprays on affected trees, as they are less effective because of insufficient uptake. Six sprays are recommended between spring and autumn, with no more than about four to six weeks between sprays.
Spraying the fungicide can cause a problem. Leaf and fruit burn is likely if phosphonate fungicide is sprayed seven to ten days before or after sprays containing dimethoate, if it is applied with copper hydroxide, or if copper hydroxide residues are present on leaves. A risk may exist with other chemicals as well, depending on the quality of the water used in the spray mixture. As a result, it is often difficult to find at least six 'safe' spray points between spring and autumn. An additional problem is that phosphonate fungicide cannot generally be mixed in tanks with endosulfan insecticide because of spray incompatibility.
How do I apply phosphonate fungicide to trees whose trunks are too small to inject?
Use foliar sprays instead (as outlined previously) or use metalaxyl granules on the ground.
What should I do if a tree dies from root rot and I want to plant another in its place?
Move a little distance away from the site of the dead tree and spend time preparing the site. Dig it over, check the pH and apply lime or dolomite as required, and put on some organic manure. Mulch the site and leave for a few months. Then apply metalaxyl granules around the tree at planting and eight weeks later. Remember to adjust the irrigation emitter and fertiliser rate for the smaller size of the newly planted tree.
Sometimes I get leaf burn after injecting trees. Is this a problem?
Leaf burn is not a problem if it is only on a small part of the tree. If it is more severe, it could affect growth. Check the phosphonate fungicide rates that you are using, inject trees only when the maximum daily temperature is above 23°C, and use a phosphonate product that is buffered to a pH of 7.0.
Fertilising
Can I use foliar sprays to apply fertilisers?
Foliar nutrient sprays are not recommended as the waxy, shiny avocado leaves reduce significant uptake of foliar fertilisers. The one exception is a foliar spray of boron before flowering where leaf boron levels are below 30 ppm. In this case, the uptake is mostly by the developing flower parts, not the leaves.
Can I mix foliar fertilisers with other chemicals?
No, mixing foliar fertilisers with other chemicals is not recommended. Foliar fertilisers are not absorbed well by mature avocado leaves and could cause burn if mixed with other chemicals.
What about using organic fertilisers like fowl manure on avocados?
Organic manures are fine for young trees up to bearing age and we recommend them at these stages. We also recommend using organic manures during the site preparation for planting. However, in bearing trees, we recommend organic fertilisers are used sparingly or not at all because the unpredictable release of nitrogen from manures may occur at the wrong time of year. This can upset the normal cycle of growth and flowering and may reduce yields.
In some sandy soil areas of Western Australia, the use of animal manures is either prohibited or restricted. Check with your local authority or Agriculture Western Australia before use.
Do I need to apply lime or dolomite each year to my orchard?
The need depends on your soil analysis results. Generally speaking, lime or dolomite is only necessary about once every two or three years. If more than 2 t/ha of lime or dolomite is needed, it is best to split the application into no more than 2 t/ha at a time, with 6 to 12 months between applications.
When should I do leaf and soil analysis?
The only recommended time for leaf analysis is when the summer flush has hardened off (generally April to May in eastern Australia and up to June in Sunraysia-Riverland and south-west Western Australia). Soil analysis can be done at any time, but we recommend soil samples be taken at the same time as the leaf samples, so the results can be interpreted together.
How do I get leaf and soil analysis done on my trees?
Buy leaf and soil sampling kits from your local fertiliser agent. These have full sampling instructions; just follow the directions. Your local fertiliser agent may take the samples for you as part of their leaf and soil analysis service. It is important that you sample the correct leaves. The other important point is to sample each variety or block of trees separately. Also avoid mixing leaves from trees of different ages together. Remember that nutrient recommendations throughout this kit are based on the results of leaf analysis by the dried tissue method. Recommendations are not appropriate for sap analysis techniques.
Irrigation
How much stored water should I have to grow avocados?
For coastal areas of Queensland and New South Wales, a water storage reserve of 5 ML/ha is recommended to maintain production in a dry year. This may be reduced to about 4 ML/ha in wetter areas, but needs to be increased up to about 8 to 12 ML/ha in drier coastal areas and inland areas such as the Central Burnett of Queensland, the Dareton district of New South Wales and the Riverland of South Australia.
In Western Australia, because of drier conditions during summer and sandier soils, a water storage reserve of between 10 ML/ha (Pemberton) and 18 ML/ha (Perth) is recommended.
Should I get my irrigation water tested?
Yes. As avocados are very sensitive to salt in the irrigation water, we recommend regular testing to ensure salt levels are within safe limits. Water salinity should not exceed 0.6 deciSiemens per metre (dS/m) with a chloride content less than 80 milligrams per litre (mg/L).
How do I know when to irrigate my trees?
Avocados are susceptible to a range of problems related to water stress, which will result in reduced yields and fruit quality. The trees have a relatively shallow root system with few root hairs, normally an important component of coping with water stress. This means that trees can be under water stress without showing visible symptoms.
As a result, irrigating according to set dates or fixed intervals is not good practice and an effective soil moisture monitoring system is recommended. The main choices are tensiometers, soil moisture sensors or capacitance probes such as the EnviroSCANŽ or GopherŽ. A less preferred alternative is to schedule irrigation according to evaporation data.
Spraying
Do avocados need much spraying?
Yes, if you want to produce top quality fruit, particularly in eastern Australia. Trees need spraying for anthracnose every two to four weeks from September to May. Where fruitspotting bug is a problem, sprays every two to three weeks over the same period may be necessary, depending on orchard location. You may also need to spray for other pests such as Monolepta beetle, tea red spider mite and leafrollers, loopers and fruitborer, as they occur throughout the season.
In Western Australia, spraying varies, depending on season and pest incidence, but some spraying in most years should be expected.
In all states, special accreditation is required to buy some chemicals.
When should I start spraying for anthracnose and fruitspotting bug?
In eastern Australia, start at fruit set (normally September-October). As the copper sprays used for anthracnose may cause flower damage under some circumstances, do not start spraying for anthracnose until flowering is completed.
In Western Australia, the critical times for anthracnose are spring and autumn. Sprays for fruitspotting bug are not required as the pest does not yet occur in that state.
How long do I have to keep spraying for fruitspotting bug and anthracnose in eastern Australia?
To be safe, we recommend spraying for fruitspotting bug until about mid-April and spraying for anthracnose until harvest. For early-producing areas, spray until harvesting, making sure you comply with the withholding periods of the products used.
I sometimes see a few Monolepta beetles in the orchard. Do I need to spray?
A few Monolepta beetles generally won't do enough damage to warrant spraying. Sometimes a few beetles may be a warning that swarms are around, so regularly inspect the orchard and adjacent windbreak trees, especially Eucalyptus trees, for at least the subsequent few weeks. Periods of rain after a significant dry spell may induce a mass emergence of the beetles, so regular inspections during these periods are essential. Keep a close watch on noted hot spots from previous seasons. Also keep in touch with neighbours for advance warning of beetle swarms in the district.
Grafting
When is the best time to graft/topwork trees?
Trees can be grafted or topworked at any time of the year, but the most suitable 'mature' budwood is available at the end of the spring leaf flush immediately before the summer flush, and at the end of summer once the summer flush has matured. We recommend that grafting coincide with these periods. Topworking is best done in the autumn so that the grafts are not subjected to harsh summer conditions.
Bees
Do I need bee hives during flowering?
Yes, if you do not have good bee activity around the orchard. Two to four hives per hectare of trees are recommended. Introduce hives when about 10% of the flowers have opened. Make sure you plan ahead and place an early order for the required number of hives. In some areas, native bees help pollinate avocado flowers.
Pruning and tree size control
My trees are starting to crowd each other. What should I do?
You need to implement some form of canopy management. Otherwise, yield and fruit quality will deteriorate and the trees will become physically more difficult to spray and harvest. The type of canopy management practice will depend on tree density and the variety. Orchards vary widely, making it difficult to provide general recommendations, so seek specialist advice.
When is the best time to prune trees?
Major pruning should be in late winter or early spring after harvesting has been completed. In later producing areas such as Western Australia where fruit are harvested in late spring or summer, pruning is best after the new crop has set. In this case, some maturing fruit will be lost during pruning. We recommend growers seek specialist advice and experiment with the timing and severity of pruning to find the most appropriate practice for their orchard.
Harvesting and marketing
How do I know when fruit is ready to pick?
It is not easy, but mature fruit has a dull appearance and there is a slight shrivelling and yellowing of the fruit stalk. If you think your fruit might be ready, check it with both a ripening test and a dry matter test.
The ripening test involves picking five to ten representative fruit and allowing them to ripen at room temperature. Mature fruit should ripen within 7 to 12 days without shrivelling, have good flavour, and not be watery. The dry matter test involves weighing a sample of flesh before and after drying, usually in a household oven or a microwave. Fruit must contain at least 21% dry matter before it can be legally sold. Fruit should pass both tests before you start picking.
In Western Australia, inspectors may randomly select and test fruit for its dry matter content. Fruit failing to reach the prescribed dry matter level may be removed from sale.
Further information
The complete Agrilink Avocado Information Kit , produced by the DPI&F, provides information on all aspects of growing and marketing avocado in Australia.
The kit includes the following sections:
- Before you start
A checklist of things you need to know before you start growing the crop. - Common questions
The 20 or so most commonly asked questions about growing the crop. - Growing the crop
Our guide for establishing, producing and marketing the crop. - Key issues
Detailed information on the key decisions affecting the crop. - Problem solver
A picture series of the common problems and how to solve them. - Contacts and references
A list of industry organisations, product suppliers, and further reading. - Index
An A to Z index to help you find information quickly.
The Agrilink Avocado Information Kit is currently out of print, however a photocopy may be obtained from the Information Centre at the DPI&F's Redlands Research Station, phone (07) 3824 9555.
For commercial enquiries on avocado, contact the DPI&F on telephone 13 25 23 between 8 a.m. and 6 p.m. weekdays; non-Queensland residents phone (07) 3404 6999. E-mail: callweb@dpi.qld.gov.au
Information contained in this publication is provided as general advice only. For application to specific circumstances, professional advice should be sought. The Department of Primary Industries and Fisheries Queensland has taken all reasonable steps to ensure the information in this publication is accurate at the time of publication. Readers should ensure that they make appropriate inquiries to determine whether new information is available on the particular subject matter.
Last reviewed 7 September 2007
