Season Update Feb 2018: Western Australia

February 2018

Grower – top tips

With Grower 1:

Although this is supposed to be a quiet time of year for us we seem to have plenty to do.

Irrigation is our highest priority over the next few weeks. Making sure the trees have adequate water during the warm weather. Checking there are no leaks, clean filters and fixing faulty controllers is of the upmost importance. It seems that if something is going to go wrong with irrigation, it happens at the hottest part of the season. We will endeavour to flush our irrigation system over the coming weeks, although it seems this is the job that always gets pushed to the bottom of the list and often missed.

Assess blocks for sunburn, wind blemish and other issues to decide on whether to hand thin once the chance of damaging heat has lessened well into March. We mostly do this on varieties that are in an “on” year and are of a higher value. Most likely Cara Cara and to a lesser degree other navels for sunburn.

Finalise fruit counts and size estimates to complete crop estimates for 2018 season.

Crop monitoring is continuous for us with particular attention being placed on blocks registered for export and the arrival of a registered crop monitor to the orchard in February ensures all our relevant records are up to date and easily accessible on their arrival.

Continue to adjust fert. program based on fruit size and/or skin texture in blocks marked for export.

With Grower 2:

Irrigation

Late summer and autumn is the best window for reducing water applications if water resources are running low. Minor water stress at this time can be tolerated without a major effect on fruit size. Prolonged water stress will however reduce fruit size, and is more pronounced when the crop load is heavy. Prolonged water stress can also influence internal fruit quality characteristics, increasing the acidity and Total Soluble Solids (TSS) of fruit, while slightly decreasing percent juice. Mid-summer and autumn leaf flush will be suppressed, which can affect next seasons flowering sites.

Nutrition

Now is the time to leaf test. Collect the smaller narrow leaves that formed in the cool conditions last spring. You can see these amongst the foliage if you stand back from the tree and have a look. Collect leaves from spring flushes that have not gone on to produce further leaf flushes or fruit.  It’s best to sample at the same time each year, sampling healthy trees of the same type. Take 3-4 leaves from each tree, sampling from all sides of the tree.

Fertiliser applications should taper right off towards the end of March. Excess applications of nitrogen and potassium after this time can cause delays in maturity and colouration and produce coarser rinds.

Rind quality

Apply GA to navels at colour break for maximum delay of rind aging and extension of harvest. 10 ppm GA may delay colour development by 20-30 days. Note: late navel colour development is more sensitive to GA.

 Copper sprays

Spray copper before autumn rains to protect fruit from fungal infections and disease. This is a good preventative strategy for potential unseasonal weather conditions. Copper works by protecting the fruit surface on which it is applied. It does not kill fungus already in fruit. Coverage deteriorates over time as fruit grows and when exposed to wind and rain. As only minor fruit growth occurs after March, an early autumn application of copper provides reasonable protection until harvest. Note: Copper can darken blemishes like wind rub.

Pests

• Monitor for leaf miner and spray young growth with white oil when detected, particularly on young trees. Oil sprays reduce leaf miner numbers by reducing egg laying and should be applied before too many eggs have been laid. New growth should be protected as soon as it is formed.
• Monitor scale crawlers and apply oil spray to heavily infested areas when crawlers are active. Consider a second release of Aphytis for red scale control if levels of parasitism are below 20%.
• Ensure you have your ants under control as they exacerbate scale problems.
• Consider releasing Green lacewings if mealybug is a problem.
• Continue to monitor fruit fly levels particularly as we head towards colour break.
• Monitor for Kelly’s citrus thrips weekly until calyx closure (around March) and Greenhouse thrips weekly on fruit to be harvested late (January – March). Take action if 5% or more fruit is infested with Kelly’s citrus thrips, 10% or more for Greenhouse thrips.

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

Seasonal outlook

From March to May there is an equal chance for a wetter or drier season for most of WA. In the Carnarvon region there is a 35% chance of exceeding the median rainfall. The outlook for daytime and nighttime temperatures for March to May is a 60-80% chance of warmer days and night for most of WA.

If you’re interested in general wind data or wind forecasts for timing spraying, checkout the seven-day forecasts for wind speed on the Bureau of Meteorology website.

Crop status and management

All varieties are in the cell expansion stage of fruit growth. Keep an eye out for colour break and record when this occurs. Colour break is when the rind changes from dark to light green. This occurs as early as mid-March for some varieties. It is an indicator for management practices (see Rind quality below).

The key management goal during the cell expansion stage is to maximize fruit size. Moderate temperatures (20 – 30°C) during January and February, optimum fruit loads and correct irrigation scheduling favors good fruit growth during this stage.

Read more:

• Fruit size management guide: Part 1
• Fruit size management guide: Part 2

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