March 2018

Grower – top tips

  • Watching for colour break to apply second GA spray on some navels designated for late harvest. See note below on GA application.
  • Planning potassium sprays for blocks identified Size profiling identified blocks that may need additional potassium sprays or that may be tracking on the too large scale for those carrying light crops.
  • Flushing whole farm irrigation system.
  • Light skirting on any low hanging branches is also being carried out
  • Currently experiencing a late season increase in pest pressure particular scale
  • Final oil sprays being applied to target high pressure patches when temps are low enough.
  • Planning copper sprays to be applied in the next 4-6 weeks before the onset of winter rains to reduce disease/fungal pressure
  • What would you like to get done if you had more time?
  • More fruit measurements would have been good

More information on management practices for the coming month is provided below.

Seasonal outlook

Generally speaking, for April to June this year the chances of wetter or drier season are roughly equal for most of WA. Exceptions to this are: 40% chance of exceeding rainfall in production regions immediately north of Perth and in April a higher chance (60%) of exceeding median rainfall south of Perth.

April to June there is an increasing chance of exceeding the median max temperature south of Perth, equal chance in region north of Perth and Kununurra and less chance of exceeding temperature in Carnarvon. For minimum temperatures, there is a similar pattern, however more likely that there will warmer overnight temperatures, than daytime.

For more information on seasonal outlooks:


Average daily evaporation rates for April are: Harvey 4.4 mm, Karnet 3 mm, Gingin 4.7 mm and Carnarvon 6.6 mm. A large citrus tree (14 meter square canopy area) will use an average of 29 – 46 litres of water each day during April in the south-west and 65 litres in Carnarvon.

Crop status and management


Most early season varieties reach 50 to 60% colour in mid to late April. Colour break is when the rind changes from dark to light green. Keep a good record of when colour break occurs in each variety in your orchard. This will help with the accurate timing of GA applications.

GA Applications for rind quality

For maximum delay of rind aging and extension of harvest apply 10 ppm GA at colour break. This may delay colour development by 20 to 30 days. Ten parts per million of GA applied at 10‑50% colour may delay colour development by 10–15 days. Note: Late navel colour development is more sensitive to GA than other navels.

Apply GA to Imperial mandarins at three-quarter colour for the management of watermark.

The level of colour break can be calculated by taking a sample of fruit from the tree. Assess each piece of fruit for the level of colour, and then look at the number of fruit with each level of colour. When most of the fruit is in the level of colour you are looking for, eg 10-50% colour then you can act eg apply GA. Monitor your fruit on the tree to see how fast fruit changes colour.

Internal maturation rates

Plan to monitor brix and acid levels of early variety fruit closely and ensure fruit meet the minimum Australian Citrus Quality Standards before harvest. Fruit that does not meet these standards will result in a poor eating experience of your fruit by consumers. The resulting consumer backlash has impacts on the entire citrus industry.

Growers in WA can send their fruit for two tests per variety for free pre-harvest testing. This free testing is part of a WA program in the industry development project that complements testing from the retail and wholesale market. Imperial mandarins in particular should be sent in for pre-harvest testing to get the best time to pick.

Harvest timing

Think carefully about the timing of harvest as this can have a significant impact on the rind quality of the current crop and on flowering and fruit set for the next season. A late harvest for any given variety will reduce flowering the following season, particularly in many mandarin varieties. For mandarins, have an early select pick, taking the largest and most coloured fruit first. This takes the load off the tree and allows the remaining fruit to increase in size.

Copper sprays

Spray copper before autumn rains to protect fruit from fungal infections and disease. Copper works by protecting the fruit surface on which it is applied. It does not kill fungus in already infected fruit. Coverage deteriorates over time as fruit grows and when exposed to wind and rain. Note: Copper can darken blemishes such as wind rub.

Copper foliar sprays can also be used for the management of snail populations, forcing them out of the canopy and onto the ground where baits await. Be careful not to contaminate ground applied snail baits with the copper spray as this will deter the snails from eating them.

Soil management

If your soil requires the addition of gypsum (for soil structure improvement in heavy soil types) or lime (to increase soil pH or make it more alkaline) now is the best time to apply.


  • Copper sprays should be applied before autumn rains to reduce the incidence of Septoria spot, greasy spot, Phytophthora, brown rot and anthracnose.
  • Monitor leaf miner and control with oil sprays when activity is detected.
  • Monitor scale crawlers and apply oil spray to infested areas when crawlers are active.
  • Continue to monitor fruit fly levels and control with bait sprays. Be prepared to increase baiting frequency and density if trap numbers indicate the need.
  • KILL THOSE SNAILS. Snail activity will increase towards the break of season and now is the best time to bait. Autumn baiting will kill adult snails before they have a chance to lay eggs. Snails are also hungry after their summer hibernation.
  • Monitor for distinctive woody galls which can grow up to up to 250 mm long and 25 mm thick on citrus twigs. These can contain hundreds of larvae. Early detection of galls in orchards is essential for preventing their spread throughout your property.

This Seasonal Update for Western Australia has been prepared by Bronwyn Walsh, WA Citrus.