April 2018

Grower talk

“Getting ready for harvest is our main focus at the moment. This includes planning picking crews and finalising marketing plan with buyers. There is also a bit of training that needs to be done such as for HARPS, Freshcare, Code of Conduct and Workforce Essentials.”

Climate update and outlook

There is an equal chance of normal rainfall for the period of May to July in citrus production regions in WA. The northern region is heading into its dry season. For temperature, there is a more than 60% chance of warmer days and cooler nights in May for the coastal regions of WA. This will drop to an equal chance of normal median day and night temperatures in June.

Evaporation and irrigation

Average daily evaporation rates for the coming month of May are: Harvey 2.7 mm, Karnet 2.1 mm, Gingin 3 mm and Carnarvon 5 mm. A large citrus tree (14 metre square canopy area) will use an average of 20‑29 litres of water each day during May in the south-west and 49 litres in Carnarvon.

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

Crop status and management

Phenology and crop development

Most early season varieties reached 50 to 60% colour in mid to late April. Some mid season varieties have now reached colour break. 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. Please note that 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.

Internal maturity development

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. The resulting consumer backlash has impacts on the entire citrus industry. 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.

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.
  • Continue to 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 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.
  • Monitor for citrus gall wasp. Galls will start to become more visible on the spring flush from last season.

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