Avocado trees may start to bear fruit in the second year, but you generally won’t harvest commercial quantities until the third year.
The average yield across all Australian orchards is a low 9t/ha. Low yields are often the result of:
- poor management of phytophthora root rot disease
- poor management of soil moisture
- poor and variable rootstocks
- poor nutrition management.
Growers using good rootstocks and good management of root rot, irrigation and nutrition can achieve average yields of over 20t/ha.
The following table provides an indication of achievable yields.
Note: Once trees form a hedgerow, a biennial bearing pattern with an 'on-year' and 'off-year' can develop especially if trees are harvested late.
When to harvest
Fruit maturity varies according to the locality and the variety. If you think your fruit might be ready, check it with both a ripening test and a dry matter test. Fruit should pass both tests before you start picking.
Pick 5-10 representative fruit and allow them to ripen at room temperature.
Mature fruit will:
- ripen within 7-12 days without shrivelling
- have good flavour
- not be watery.
Dry matter test
Weigh a sample of flesh before and after drying. You can dry the fruit in an oven or microwave. The industry recommends that Hass fruit should have reached at least 23% dry matter and Shepard fruit should be at least 21% dry matter before harvesting.
Harvest ing process
Avoid picking fruit when wet or fully turgid as this increases the risk of postharvest rots, sensitivity to mechanical abrasion and lenticel damage. The Hass variety can be ‘snap’ picked (plucked from the tree) but should be ‘snip’ picked (cut from the tree with a pair of special secateurs) if there has been recent wet weather or if it’s the start of the harvest season. Varieties other than Hass should also be ‘snip’ picked.
Avoid picking fruit during hot weather as this will shorten the shelf life of the fruit unless the field heat can be removed within a few hours of harvest using forced air-cooling.
It is important to handle fruit carefully at all times and to minimise all fruit drops - this will avoid skin damage, bruising and rot development. Adopt practices such as:
- lowering picking bags into bins before gently releasing fruit
- minimising walking time for pickers to reach a bin
- taking care during transportation of bins to the packhouse.
It is important to keep harvested fruit cool and shaded. This can be done by covering bins with a cover or green branches, or by placing bins in the shade.
Packhouse and cool chain
Always aim to pack and cool fruit within 24 hours of harvest, especially if the fruit is destined for export or expected to remain in the supply chains for more than 2 weeks.
The temperature for cooling hard, green mature fruit depends on the variety:
- 4°C to 5°C for Hass with a maximum storage time of 4 weeks
- 6°C to 8°C for other varieties with a maximum storage time of 2 weeks.
It’s recommended that forced air-cooling be used if warm fruit needs to be cooled before packing. This is a more effective way of removing heat from fruit than room cooling (up to 10 times faster) as well as preventing condensation developing.
If the fruit is brushed and cleaned, it is important to ensure soft brushes are used and the line speed and volume load is carefully managed to minimise fruit damage.
Registered postharvest fungicides should be applied to fruit within a few hours of harvest. Follow the label instructions for exposure time for effective coverage and timing after harvest.
Grading and packing lines should be short and padded to prevent fruit damage, and also cleaned regularly. Avocados are usually graded as Premium, Class 1 and Class 2. Grading should be conducted by trained staff who are aware of the specifications required for each class, as well as those that are rejected.
Single-layer trays or cartons are used to pack avocados depending on grade and destined market. It is important that the packaging used provides sufficient ventilation for air movement to help keep the fruit cool.
Avocados need to be cooled as soon as practically possible after picking and after packing to maintain quality. Avocados should be thoroughly cooled and target temperatures maintained throughout the entire cool chain to ensure the preservation of fruit quality. It is important to cool fruit before transportation, and not to rely on refrigerated trucks for this as these trucks can at best only maintain the existing temperature.