Poor conditions, plenty of good results?

Plenty of North Queensland avocado growers did a good job of producing quality avocados this year despite an exceptional wet season which disrupted spray programs and delayed picking (Figure 1). The bulk of North Queensland packers (12 packers) sampled in AV22011 retail quality monitoring this year achieved average fruit acceptability above the industry standard of >90% of fruit with less than <10% internal defects. The average acceptability of all 98 retail quality samples from these 12 packers was 96%.  Of the 3 packers that achieved an average fruit acceptability below 90%, the average of their 29 retail quality samples reported was 88% acceptable.

Figure 1. How internal defect levels differed in 2024 between North Queensland packers whose samples averaged above or below the industry standard (90% of fruit with <10% internal defects).

You wonder how this is possible when actual rainfall exceeded the long term mean from November 2023 to April 2024, ranging from a 40% to almost 500% extra (Figure 2). The number of wet days per month also exceeded the long term mean from December 2023 to April 2024 (Figure 3). In February 2024 there were 7 “dry” days and only two were consecutive. In reality there was probably only one or two spraying opportunities in each of January, February and March.

Figure 2. Walkamin actual and mean monthly rain (Nov. 2023 – May 2024).

Figure 3. Walkamin actual and mean monthly wet days (Nov. 2023 – May 2024)

Although the season is behind them now, their lessons are certainly applicable to other districts. In talking with a couple of North Queensland growers recently, 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.

The systemic fungicides, Switch® and Score® (Permit 94009) were particularly useful when applied after periods of extended rainy weather when coverage with protectant fungicides (e.g. copper) was difficult to maintain.

Remember that a high proportion of Colletotrichum (cause of anthracnose) in Queensland is resistant to strobilurin fungicides. Samples of Colletotrichum from a range of orchards were tested by Liz Dann and her team to discover that 60% from north Queensland, 65% from central Queensland and 65% from southeast Queensland were resistant.

For the simple method to test if your Colletotrichum is resistant and to discover the latest recommendations for orchard fungicide usage click HERE for Liz’s article on the BPR.

For further information on AV22011 monitoring results and quality management resources, click HERE or contact John Agnew from the Queensland Department of Agriculture and Fisheries (john.agnew@daf.qld.gov.au) or Anne Larard (idm@avocado.org.au) from Avocados Australia.

This article appears as part of the 4 October 2024 issue of Guacamole, AAL’s enewsletter.

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