A recent study in regional Victoria has brought to light the impact of blackberries on Queensland fruit fly numbers.
The research highlights a further detrimental impact that blackberries can have on fruit production and the environment, with the study finding evidence that the pest insect used the blackberry fruit as a harbour for reproduction.
Australia Biological director Robin Adair conducted the central Victoria survey during the 2023 season and found a correlation between the number of larvae and adults emerging from blackberry fruit and the number of adult fruit flies trapped on the same stand of blackberries.
The study’s report said there was now a ‘compelling incentive’ to reduce blackberry infestations.
Up to two cycles of fruit fly can occur during the blackberry fruiting season (January to March).
More fruit flies were found in sample sites closer to suburbs and fruit growing regions than in remote locations.
Dr Adair told Country News he was surprised to find Queensland fruit fly so ‘extensively’ established on blackberries in Victoria.
“The need for action is clear: we need to push harder for blackberry control,” Dr Adair said.
“Particularly in and around towns to help with the Queensland fruit fly control program as well as protecting our environment and recreational assets from this terrible weed.”
The Victorian Blackberry Taskforce (VBT) assisted Dr Adair with the work and provided grant money for the project.
VBT chair Lyn Coulston said the results affect both growers and gardeners.
“(The results) are another engagement tool to say ‘here’s another reason to control blackberry’,” Mrs Coulston said.
“You don’t want to leave harbour for them.”
As part of the study, Eco-lure insect pheromone traps were hung between one and two metres from the ground within the plant’s canopy.
The traps are able to attract adult fruit flies from 400 metres away.
From the 35 locations where fruit fly were trapped, the highest numbers were recorded at the Seymour, Chiltern, Euroa and Shepparton sites.
Dr Adair’s report said that the polyphagous behaviour of the insect meant that it could alternate between different fruits.
Seventy per cent of sites where adults fruit flies were trapped also had either adult or juvenile fruit fly emerge from blackberry fruit.
The number of insects was not related to the density of the blackberry infestation.