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Ongoing project

Investigation into citrus blossom bugs in avocados (AV19000)

Key research provider: The Queensland Department of Agriculture and Fisheries

What’s it all about?

Beginning in 2019, this investment is developing an understanding of the biology and ecology of citrus blossom bug and its impact on the Australian avocado industry. Ultimately, this project will produce a guide for growers to help them protect their crops from the insect, monitor for the bug and manage any infestations.

Citrus blossom bug is currently thought to reduce floral production on citrus trees in coastal districts by killing the small flowers shoots – but an increasing number of avocado growers are also reporting poor crops due to this pest. At present very little is known about the lifecycle of the citrus blossom bug, how it is distributed and whether it has any natural enemies. This project will deliver the knowledge on this pest that is needed to ensure that effective management strategies can be developed.

Project activities include, but are not limited to:

  • Conducting a comprehensive literature review of citrus blossom bugs and related pests in avocado and similar industries, including current management methods used for similar pests

  • Field studies to determine the taxonomy and pest status of the pest, such as whether citrus blossom bug damage affects flower set, fruit set and yield

  • Studying the biology and ecology of the pest, including identifying key natural enemies, lifecycle stages, and potential host range

  • Compiling data on the efficacy of current management methods and identifying possible new strategies.

The research team conducted an intervention trial in a commercial orchard during the 2022 avocado flowering period to further evaluate the pest status of citrus blossom bug and study several aspects of its biology and ecology.

Several blocks of avocado were selected for use in the trial which consisted of three different cultivars (Hass, Sharwil and GEM). Approximately half of each block was selected for treatment with a chemical insecticide regimen.

After insecticide applications, the citrus blossom bug populations were monitored weekly in each of the trial blocks until fruit set. Estimates of damage were also recorded throughout the trial and subsequent fruit set rates within the trial blocks were also measured.

Application of the insecticide regimen proved effective for controlling citrus blossom bug populations in all cultivars and significantly reduced the amount of observable feeding damage to avocado flowers. The insecticide application also significantly increased fruit set rates in one of the cultivars used in the trial.

A preliminary report on the biology and ecology of citrus blossom bug has been completed since the team’s last update.

Progress towards the intermediate outcomes – understanding the pest status, biology and ecology of citrus blossom bug (CBB), its industry impact, and identification of future research needs – was made by completing the second season of field collections and conducting a preliminary intervention trial. Collections were made from across Queensland, however they could not be made in NSW due to COVID19 travel restrictions.

Observational studies of CBB biology led to a preliminary description of feeding behaviours in the context of avocado, as well as identification of the eggs and suitable oviposition sites within avocado inflorescence.

Results from a small-scale field trial suggest that Transform® Isoclast® may be a suitable option for managing CBB. Application of the insecticide was shown to decrease the visible signs of mirid feeding damage to inflorescence and improve fruit set in one of the cultivars used in the trial.

Since commencement of the project, research has included a preliminary taxonomic study of first-season field collections from Far North, Central and South-East Queensland. The study confirmed clear differences between male and female citrus blossom bug (CBB). It also showed differences between North Queensland specimens compared with those from Central and South Queensland, with further investigation ongoing.

A preliminary field trial was conducted to evaluate the damage caused by CBB to avocado crops and its pest status. The results were inconclusive, with work also continuing in this area.

Related levy funds

This project is a strategic levy investment in the Hort Innovation Avocado Fund