Articles (BPR) Archive - Page 23 of 23

Principles of Avocado Canopy Management

This video explains why canopy management is so important for avocado and outlines the main principles. However, a prescriptive approach cannot be provided since growing environments and management styles vary widely and no two orchards are ever the same. A canopy management plan needs to be worked out to suit each orchard.

Mainstream avocado canopy management options

The video below outlines some canopy management options for Hass and Shepard orchards planted at conventional spacings on the east coast of Australia where trees don’t have fruit on the tree all year. It complements the above video. Click on the image below to access the video.

The videos above were produced by DAF as part of project AV17005 “Avocado industry development and extension”.

Jump to these sections in the article:
Acknowledgements
Reasons for canopy management
Rules of thumb for tree size
When to prune?
Cropping Patterns

Acknowledgements

This publication formed part of project AV04008 and was funded using the Avocado Industry levy and funds from the Australian Government through Horticulture Innovation Australia Limited. All dollar values within this publication are estimates only provided as a relative guide of costs.

Thanks to all growers who provided information on their canopy management operations including: Agriexchange Pty Ltd; Avowest; Balmoral Orchards; GJ & MM Burch; Coastal Avocados; Delais Orchards; Donovan Family Investment Trust; CF Fechner; Gala Orchards; Hilltop Mareeba; Lavers Orchards; I & R Philpott; D & D Roche and Son; Simpson Farms Pty Ltd; Smerdon Enterprises Pty Ltd; Thistledome Farms; Toohey Farming and Yaldon Park. Simon Newett (Queensland Department of Agriculture and Fisheries) and Lachlan Donovan (Donovan Family Investment Trust) provided valuable comments and contributions in compiling this booklet.

Reasons for canopy management

• Optimise light interception and penetration into the orchard
• Maintain inter-row space for machinery access
• Reduce harvesting costs and improve picker safety
• Improve efficiency of spraying operations to control pests and diseases
• Maximise yields and fruit quality

Insufficient light due to crowding results in dieback of inner and lower branches creating large unproductive areas.

Large trees are more costly and more dangerous to harvest.

Rules of thumb for tree size

For optimum levels of sunlight to reach the tree canopy:

1. The height of the tree should not exceed 80% of the distance between tree rows.

Table 1 Relationship between tree height and distance between rows

2. Tree height should be less than 2.5 times the width of the canopy-free inter-row space (e.g. If requiring a 2m clearance for machinery access down the row, the maximum tree height should be 5m.)

3. No part of the tree canopy should be more than 2 to 2.5m from direct sunlight. Maximum canopy width should be 4 to 5m. Note: this is the ideal theoretical situation but is often impractical. In cool production areas with low vegetative vigour it can be achieved in very high-density plantings with upright varieties such as Reed and Lamb Hass.

When to prune?

Pruning time will depend on the growing environment. Knowing the cropping cycle is important in determining when trees are best pruned.

Cropping patterns

Shoot growth, flowering and fruiting cycles vary from region to region.

Less than 12 months from flowering to harvest:

In warm subtropical climates (e.g. North and Central Queensland and coastal areas of South-East Queensland) the crop can be harvested up to several months prior to next season’s flowering.

Table 2 Growth cycles for Shepard avocado in North Queensland

Table 3 Growth cycles for Shepard avocado in Central Queensland

Table 4 Growth cycles for Hass avocado in North Queensland

Table 5 Growth cycles for Hass avocado in Central Queensland

Table 6 Growth cycles for Hass avocado in coastal areas of South-East Queensland

In these environments pruning operations are normally done after harvest and prior to flowering. Follow up pruning to remove watershoots and to reduce the spring growth flush are often made in summer.

More than 12 months from flowering to harvest:

In cooler temperate climates (e.g. hinterland areas of Southern Queensland and Northern NSW, Central NSW) and Mediterranean climates (the Tristate region and south-west Western Australia) it is normal for the tree to carry two crops for a period of time. Mature fruit as well as the current season’s crop.

Table 7 Growth cycles for Hass avocado in hinterland areas of Southern Queensland

Table 8 Growth cycles for Hass avocado in Northern New South Wales and Mid North Coast New South Wales

Table 9 Growth cycles for Hass avocado in Central Coast New South Wales and Mid North Coast New South Wales hinterland

Table 10 Growth cycles for Hass avocado in the Tristate region

Table 11 Growth cycles for Hass in the Perth region in Western Australia

Table 12 Growth cycles for Hass in Bunbury and Bussellton region in Western Australia

Table 13 Growth cycles for Hass in south-west Western Australia

In these environments, pruning after harvest will not only remove flowers and developing fruit but can also expose this fruit to sunburn. Pruning (typically selective limb removal) is often carried out after the “on” year harvest and when trees are in an “off” year to minimise fruit loss. Mechanical tip pruning of young trees in late autumn has also been used in these environments.

Key resources

Revised orchard fungicide programme for anthracnose in avocado – Liz Dann (4 pages)
Given the recent granting by APVMA of an Emergency Use Permit (PER94009) for
Score® and Switch® fungicides, and resistance in Colletotrichum to strobilurin
fungicides (e.g. azoxystrobin), it is time to revise the orchard fungicide programme.

» Presentation: WA AvoSkills 2020 – ‘Diseases (other than Phytophthora) and their management in avocado’ – Liz Dann (33 slides)

» Presentation: Tamborine Northern Rivers Regional Forum 2022 – ‘Fruit diseases of avocado and how to manage them’ – Liz Dann (29 slides)

Key information

Anthracnose is a serious fungal disease in Australia that is second in importance only to Phytophthora root rot.
Anthracnose is widespread and causes fruit rots which only become evident when fruit ripens. For this reason, affected fruit are not seen by growers and packers but only become evident once fruit ripen after purchase. This results in a serious loss of consumer satisfaction and buying confidence.
The spores germinate on wet fruit and remain dormant and unseen until fruit ripens.
In Hass the problem is further masked by its thick, dark skin.
There is a high incidence of anthracnose in the warm summer rainfall regions of Queensland and New South Wales.
In Western Australia there is a different species of the pathogen adapted to cooler conditions, so anthracnose is also an issue in this region.
In the Tristate region anthracnose can be an issue when rain occurs and/or overhead misting is used.
For effective control, an integrated pre-harvest and postharvest approach is needed that includes the following practices:

◦ Where possible, choose a rootstock which has a proven history of producing more robust fruit e.g. Velvick.
◦ Maintain a protective layer of registered fungicide (mostly copper protectants) on the fruit from fruitset right through till harvest by applying foliar sprays every 14 to 28 days. The spray interval depends on weather conditions.
◦ Canopy management conducted to allow better light penetration and picker access will also improve ventilation and fungicide spray coverage.
◦ Practice orchard hygiene by removing sources of spore inoculum from the canopy including old fruit and, if possible, dead branches and twigs.
◦ Maintain good pest control and also take steps to reduce wind rub to fruit as any type of skin damage predisposes fruit to infection.
◦ Apply a balanced nutrition programme to promote the development of robust fruit. This entails having sufficient calcium available and not applying excess nitrogen.
◦ Do not harvest in the rain or at any other time when fruit is wet.
◦ Apply a registered postharvest fungicide to fruit within 24 hours of picking.
◦ Avoid delays between picking, packing and dispatching fruit, and maintain the cool chain from harvest onwards.

Anthracnose causes severe internal damage to fruit. Damage is characterised by a flesh rot that expands hemispherically from the point of infection.