September Citrus News ’25

Protecting Our Orchards – Citrus NZ Biosecurity Resources

Orchard biosecurity is vital for protecting your property against new and exotic pests, diseases and weeds, while also reducing the impact of those already present in New Zealand.

This month we’re highlighting a range of Citrus NZ resources available to help you strengthen biosecurity on your orchard. These can be downloaded from the members portal on the Citrus NZ website, or hard copies can be requested by emailing . Key resources available:

Factsheets for Asian citrus psyllid (ACP), Huanglongbing (HLB) and citrus canker
Learn about these exotic pests and diseases that have impacted citrus production worldwide.

Citrus Orchard Biosecurity Poster
A practical overview of steps you can take on your orchard to reduce biosecurity risks — from recognising risks and knowing your crop, to good hygiene practices, quality inputs, and accurate record keeping.

Citrus Orchard Management Calendar
Now updated with guidance on when and how to scout for ACP.

ACP Monitoring Guide
Step-by-step instructions on monitoring for ACP, including what to look for, where to look, and why monitoring is essential.

ACP & HLB Biosecurity Response Guide
An outline of what happens in a biosecurity response, what MPI’s Response Team does, and what it means for your orchard if you’re in a response zone.

 Spotlight on Xylella fastidiosa

Xylella fastidiosa is one of the world’s most serious plant diseases and a significant threat to the citrus industry. This invasive bacterium causes citrus variegated chlorosis, blocking water movement in plants and leading to leaf scorch, chlorosis, dieback, reduced fruit size, and lower yields.

With the ability to infect more than 600 plant species, including native, horticultural and ornamental plants, its impact overseas has been devastating — severely affecting grapes, olives, stonefruit, and citrus.

Citrus NZ is working with MPI and other GIA partners (NZ Wine, Summerfruit NZ and NZ Plant Producers Inc) to mitigate the risk, by building and raising awareness of the of this disease.  An awareness campaign is about to launch to raise understanding of this disease and its potential impact.

Learn more about Xylella fastidiosa and the diseases it can cause in citrus, grapes and stonefruit on the MPI website.

Market Access – Meyer Lemons to Korea

There has been recent progress with gaining access for Meyer lemons to Korea. Korean authorities are currently analysing the pest risks associated with importing Meyer lemons and requested further information on some pests. Citrus NZ has now provided this, which will help Korea complete its Pest Risk Analysis.

We are hopeful that this stage will be completed quickly, after which we can work with MPI to determine how any pests of concern may be managed.

In parallel, Citrus NZ is commissioning a market analysis report to better understand the commercial opportunities for Meyer lemons in Korea. We will consult with growers on the findings and next steps before progressing further.

Navel supermarket monitoring for the 2025 season completed

The 2025 season of monitoring NZ navel orange maturity across the three main supermarket Distribution Centres has just wrapped up. This 10-week programme ran from 30 June to 1 September, with weekly sampling conducted by QC staff at each Distribution Centre.

Each sample consisted of 16 fruit, which were tested for Brix and acid. Over the course of the programme, a total of 44 samples were collected, comprising 704 individual oranges.

An analysis of the data will be completed shortly, and a final report on the programme will be prepared and made available through Citrus NZ.

We’d like to extend our thanks to the QC teams from Woolworths and Foodstuffs, and to everyone who contributed to supporting this year’s programme.

Getting Nutrition Right for Strong Growth and Fruit Set

September and October mark the beginning of the new spring flush on our citrus crops. Citrus are highly efficient at taking in foliar nutrition, making September the ideal time to begin your foliar nutrition programme for the season. Wait until there is sufficient new flush to provide a decent surface area for uptake. While new growth has started, it will likely be another couple of weeks before there is enough leaf area for effective application.

Bud formation has already been set in the tree, so the focus of early foliar products should be on encouraging growth and promoting fruit set. Calcium is especially important at this stage, as it builds strong cell walls, supports flower development, and helps establish fast-growing fruitlets. Magnesium is also critical in spring, preventing chlorosis (yellowing) and supporting chlorophyll production. The most effective and economical way to deliver these is through Calcium or Magnesium Nitrate at a standard rate of 1.25 kg per 100 litres (25 kg per 2,000 litre tank). These products also provide nitrogen to support rapid tree growth.

To this base, add your micronutrients. If leaf testing has shown deficiencies (e.g. Zinc), target them with specific products. Otherwise, use a balanced multi-element mix available from most retailers to maintain and enhance micronutrient levels at this important stage.

If possible, applications can be further enhanced with seaweeds, elicitors, or products designed to support flowering and fruit set. These can help reduce stress caused by waterlogging, drought, heat, or cold, all of which can contribute to fruit drop. Supporting trees through this period of stress can improve fruit set outcomes.

Remember, foliar nutrition alone cannot meet all the nutritional needs of your trees or future crop. The majority of nitrogen must come from ground applications. Once soil temperatures reach 12–15°C, fertiliser can be applied to the soil. Before this point, trees remain relatively dormant and are less effective at taking up nutrients from the ground.

For more detail, see the recently added Citrus NZ Growing Citrus in New Zealand Guide on our website and in our guide.