Avocado industry capacity building – Western Australia (AV17006)

Over the past six months, the project team has continued monitoring activities for the avocado fruit load management experiment being conducted just outside of Manjimup, WA. Data collection in the fruit load experiment has included the collection of soil and leaf samples, regular counting of retained fruit on the trees and measuring tree volume and other growth parameters. Harvest and application of third thinning treatment were performed in January. Electronic monitoring of the trees via Supplant equipment continues. From the three years of crop load manipulation experiments emerged a behavioral trend showing less variability in fruit retention between years in trees thinned to 1 fruit per fruiting inflorescence and therefore, reduced effects of irregular bearing. After consultation and with full support of the PRG group, a contract variation to verify this trend for additional 10 months has been submitted and accepted.

Support of other research projects includes finalising the Avocado fruit consignment tracking for AV18000. Two additional project to benefit WA Avocados have also been successfully tendered for and subcontracts between QDAF, as leading agency, and DPIRD are under signature: AM21000-Serviced Supply Chain II focused on fruit export and AV21005-Avocado fruit robustness. The support to the WA Agriculture Produce Commission project on understanding the effects of climate on avocado flowering is also ongoing. Extension materials developed during the period from January 2023 to May 2023 include the organization and delivery of an avocado seminar/workshop in Manjimup on May 30 2023. 

A series of talks all related to avocado production, pollination, pests, latest experimental results and future research plans were presented. An abstract has been accepted to be presented as poster at the ISHS International Symposium on Tropical and Subtropical Horticulture in Mediterranean Climate in Palermo, Italy (09 to 12 October 2023). A poster was presented at the 10th World Avocado Congress in New Zealand (3-5th April).

The project team has continued their monitoring activities for the avocado fruit load management experiment being conducted just outside of Manjimup. Data collection in the fruit load experiment has included the collection of soil and leaf samples, collection and counting of dropped fruits, regular counting of retained fruit on the trees and measuring tree volume and other growth parameters. Harvest and application of third thinning treatment were performed on January 15th and 18th respectively.

Electronic monitoring of the trees via Supplant equipment continues. At this stage of the fruit load experiment the treatment thinned to one fruit per inflorescence carries the most fruit with the control carrying the least. While the one fruit per inflorescence treatment has the highest number of fruits the efficiency of the canopy is roughly the same as the three fruit per inflorescence treatment due to reduced tree growth. From the two years of crop load manipulation experiments emerged a behavioural trend showing less variability in fruit retention between years in trees thinned to 1 fruit per fruiting inflorescence and therefore, reduced effects of irregular bearing.

Extension materials developed during the period from May 2022 to January 2023 include the organisation and delivery of an avocado seminar/workshop in Manjimup on June 22nd 2022. A series of talks all related to avocado production, pollination, pests, latest experimental results and future research plans were presented. Over 30 growers and industry operators attended. A poster on the usage of the Rubens fluorometer in avocado non-destructive fruit quality measurements was presented at the IHC2022, the ISHS horticulture world congress, in Angers France in August 2022.

Since the last update, the project team has contributed to capacity building and productivity research in several ways.

• Experiments investigating the removal of fruit from inflorescences early in the season continued. Fruit from previous-season manual thinning was harvested, with new thinning treatments applied. Tree and fruit growth, leaf chlorophyll content and soil and leaf analysis continued to be monitored. Electronic soil, fruit and trunk monitoring was installed.
• The first year of crop load management data indicated that tree growth (volume and new shoot growth length) with 3 fruit left for inflorescence has the least amount of vegetative growth, while at the same time having comparable total fruit numbers on trees, indicating higher carbohydrate distribution toward fruit. Return bloom and bloom with fruit set was also affected with the 1 fruit treatment having the most inflorescences with fruit set, while the control had the least inflorescences with fruit set, despite control having the most inflorescences per tree.
• Additional experiments investigated the presence of fungal inoculum and resulting negative effects on fruit when harvested wet, if left untreated or after undergoing dipping treatment with fungicide. Timing of the dipping treatment after harvest (within 2 hrs, after 24 hrs and after 48 hrs) was assessed, with data still under evaluation.

ACT NOW

Read this article from the project team, Is fruit set related to weather at spring? A retrospective analysis, published in Talking Avocados, Spring 2021, pages 71-74

Developments in capacity building and productivity research for the sector has continued with:

• Results from the desktop review into weather conditions related to avocado fruit set were compiled into an industry report, which will be available soon
• Growers and industry representatives were hosted at the DPIRD station in Manjimup during May 2021, where information about supply chain monitoring and fruit quality evaluation from project Implementing best practice of avocado fruit management and handling practices from farm to ripening (AV18000) was shared. An overview of the facility and the work it performs will be shared with growers as part of a Japanese export workshop, which is planned for June.
• Preliminary consultations were held with select growers about managing the performance of fruit harvested in wet or moist conditions. The growers showed interest in evaluating the timing of fruit dipping after harvest, with an experiment to be implemented in the coming season.
• Experiments to investigate irregular bearing and sustainable crop load management commenced, assessing the hypothesis that by removing fruit from inflorescences early in the season, trees will not waste carbohydrates on fruit that will not mature. The trial also uses new soil, fruit, leaf and trunk monitoring technology, helping growers understand this capability. Early trial results have been promising, indicating some positive response to treatment.

Over the last year, the project team have made progress on the following activities:

• A desktop study into weather conditions that may have affected avocado fruit set during the spring of 2019 was performed to compare weather, temperature and other environmental conditions for three major avocado growing areas. Unfortunately, given the current understanding of avocado flowering and fruit set requirements, it was not possible to pinpoint a reason for the poor fruit set without performing more extensive measurements.
  
  
• Capacity building activities included a series of presentations on phytophthora root rot and six spotted mite that were hosted in December at DPIRD station in Manjimup.
  
  

Investigation into irregular bearing and sustainable crop load management

This project has been extended to allow for an investigation into irregular bearing and sustainable crop load management in avocado. This research will explore the hypothesis that by removing fruit from inflorescences early in the season, trees will not waste carbohydrates on fruit that they will not bring to maturity and would be dropped in stages. This will allow trees to utilise carbohydrates more efficiently and keep more fruit, increasing overall grower profitability. The experimentation also aims to implement and highlight to growers the usage of technology for the monitoring of several aspects of plant physiology and behaviour and to collect the needed data for the evaluation of the experiment.

The research will produce recommendations to growers on sustainable crop load management and on the adoptability and use of current monitoring technology to facilitate decision making toward a more efficient orchard management. The extension will also further develop capabilities for the industry by generating industry and scientific publications. Examples of technology being evaluated include dendrometers, whole tree monitoring with autonomous stations, and leaf chlorophyll meters.

With project activities now in swing, Western Australian growers are encouraged to reach out to research officer Declan McCauley on 08 9777 0184 or at declan.mccauley@dpird.wa.gov.au for any information or queries relating to his work.

As well as communicating best practice in avocado growing in the state, one specific area of research for the project has been identified, with work being conducted into fruitlet drop shortly after flowering, after fruitlets have exceeded a size of 5.5mm. Here, Declan’s work is tying into that of another Hort Innovation Avocado Fund project, Maximising yield and reducing seasonal variation (AV16005).

ACT NOW

Learn more about Declan in this profile piece, run in the Department’s March 2019 e-newsletter.

The project has also been updating resources for avocado growers on the Department’s website, including…

• This overview of avocados in Western Australia 
• Information on avocado industry regulation in Western Australia 
• Flowering, pollination and fruit set in avocados 
• Details on irrigation principles in avocado production.

Declan Macauley has been appointed as the new state-based Research Officer, within the Department of Primary Industries and Regional Development, Western Australia. With the officer role in place, initial project activities will include conducting consultation and a ‘needs analysis’ in conjunction with the Western Australia avocado industry, to help guide the specific work and areas of focus for the project.