June 2018

Climate update and outlook

There is a 50-55% chance of exceeding rainfall for the period, July to September across WA. WA is likely to have warmer than average nights from July to September. North of Exmouth and south of Waroona are also more likely to have warmer days than average.

Evaporation and irrigation

Average daily evaporation rates for the coming month of July are: Harvey 2.3 mm, Karnet 1.8 mm and Carnarvon 3.7 mm. A large citrus tree (14 metre square canopy area) will use an average of 17 to 25.5 litres of water each day during July in the south-west and 36 litres in Carnarvon.

For more information on seasonal outlooks: http://www.bom.gov.au/climate/outlooks/#/overview/summary

Crop status and management


For next seasons’ fruit we are now in the floral induction stage where buds in the tree are making the transition from vegetative to floral buds. Cooler temperatures during winter induce citrus buds to flower. The number of flowers produced and the proportion of different types of flowers is strongly influenced by crop load in the previous season. Most flowers are produced on shoots that grew during the previous year. If you would like a chart of the key phonological stages for citrus please contact Bronwyn, industrymanager@wacitrus.com.au.

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.

Internal maturity development

Good results have been seen with pre-harvest testing and market testing for WA oranges and mandarins. Keep monitoring fruit maturation rates closely for new varieties to ensure it meets Australian Citrus Standards before harvest. Hickson mandarins have been variable in results in previous seasons so be vigilant. Fee-for-service payers can have the internal quality of fruit independently tested without charge (two samples per variety per grower). Just drop your samples to any agent at Market City.

Monitor development of internal maturity of fruit closely and ensure fruit meets at least the minimum Australian Citrus Quality Standards before harvest. Supplying fruit that does not meet these standards places poor eating quality fruit into the mouths of consumers. WA citrus fee-for-service payers can have the internal quality of fruit independently tested without charge (two samples per variety per grower). Just drop your samples to any agent at Market City, Canning Vale.

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.


Oleocellosis is rind damage resulting from rough picking and handling of fruit. Damage does not fully appear for up to 4 days after the injury/damage occurred and can significantly reduce the value of your fruit. To minimise oleocellosis, harvest in the warmest part of the day and pick from the northern side of the tree first. As a rough guide, ambient air temperatures should be above 12°C, however a wet bulb temperature and rind oil release pressure test should be conducted to provide a more reliable guide. It is best not to harvest if fruit are wet.


A well-pruned canopy with a good distribution of strong bearing shoots close to main scaffold branches promotes leafy inflorescences. Pruning after harvest therefore assists in balancing crop load if heavy flowering is expected.

Preparation for flowering

After harvest consider foliar applications of urea and micro nutrients to promote flowering for the next season particularly if you suspect a light flowering year. Do not apply urea if you expect a heavy flowering. Management of nutrition, irrigation and pruning now may prevent granulation issues next season.

Pest, diseases and weeds

  • Continue to monitor fruit fly levels and control with bait sprays, especially as dry warm autumn keeps flies active. Be prepared to increase baiting frequency and density if trap numbers indicate the need.
  • Monitor scale and mealy bug and apply oil spray to infested areas when crawlers are active. This will help you take the correct action when determining control programs for the spring and summer period when juveniles of these pests are active.
  • Monitor for citrus gall wasp. Galls will start to become more visible on the spring flush from last season.
  • Practice on-farm biosecurity to protect your investment, http://www.farmbiosecurity.com.au/

Grower tips

  • Planning for residual herbicide applications with rains to wash it in
  • Timing for second application of stop drop on late harvest navels
  • GA would only be planned for flower regulation of next crop if expecting a heavy flower.
  • Second application of copper sprays
  • Pruning has started on early varieties that have been harvested and will follow on behind the pickers
  • We are seeing the emergence of baby snails after all the rain we have been having, so baiting is an ongoing focus going forward
  • Picking in the right conditions and avoiding unnecessary rough handling of fruit during picking or transport of fruit will help to avoid oleocellosis

We are keeping a close eye on citrus canker developments.

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