Grabbing the opportunity to apply fungicides

By John Agnew & Shanara Veivers, QDPI

Many NQ packers achieved good fruit quality last season, despite wet weather leading to harvest.

Their success was due to determination to get as many key factors contributing to quality as perfect as possible. That included grabbing any opportunity to apply fungicides, ensuring dispatch temperatures were ideal, and matching supply to orders to minimise time to customer.

This season is also proving to be challenging, with the number of wet days per month generally exceeding the historic mean in North Queensland and Central Queensland (Figure 1).

Above, Figure 1. Walkamin and Childers wet days per month, actual versus historic mean (BOM, 2025).

NQ growers about to harvest can benefit from the following actions:

1. Pre-harvest sampling to determine potential disease load:

Take extra fruit when sampling for dry matter testing and store in trays in a warm, humid place. Assess internally at medium soft ripe stage.

2. Conduct a Roll Test on randomly sampled fruit to determine potential for lenticel damage.
3. Ensure a registered and market-approved post-harvest fungicide is applied, following label instructions.
4. Measure fruit pulp temperature to ensure that it is at the correct temperature (7°C for Shepard, 5°C for Hass) at dispatch. Dispatching at 2 – 3°C above recommended has been recorded in a significant number of consignments in 2024.

Growers in CQ, SQ & CNSW can benefit from maintaining a robust and responsive spray regime as follows:

1. Use BOM Tools to predict rainfall weekly (Figure 2)

Rainfall – Chance of at least 15 mm in 3 days for 15 Feb – 28 Feb – Climate Outlooks

2. Use protectant copper sprays every 28 days from after flowering to harvest but reduce interval to 14 days during wet weather #. (Figure 3)

# Wet weather is defined as at least 3 consecutive days with ≥ 1mm rain.

3. During prolonged wet periods = substitute copper with a systemic/protectant spray such as Score® or Switch®. This will offer a new barrier of protection on the fruit and address any infection started during this wet period. Abide by Permit conditions PERMIT94009 .

Above, Figure 2. BOM Climate Outlook Tools predict the chances of at least 15mm of rain in 3 days for 17-23 February at Tolga: 14% chance of <15mm, 46% chance of >40mm and 24% chance of >99mm.

Above, Figure 3. Childers “Ideal” orchard fungicide applications (orange vertical lines) based on actual rainfall frequency (blue lines) during 24/25 season to date.

For further information on AV22011 quality management resources, contact John Agnew from the Queensland Department of Primary Industries (john.agnew@daf.qld.gov.au) or Anne Larard (idm@avocado.org.au) from Avocados Australia.

This article appears as part of the 17 February 2025 issue of Guacamole.

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