This information has been commissioned by the Goulburn Murray Valley Area Wide Management Fruit Fly Program and is funded by the Victorian Government. Use of this material in its complete and original format, acknowledging its source, is permitted, however unauthorised alterations to the text or content is not permitted.
Fruit fly activity
Queensland fruit fly (Qfly) activity, as measured by the numbers of fruit fly trapped per trap on a grid of over 300 traps across the Goulburn Murray Valley (GMV) region, has been steadily increasing since September 2022. The pace of increased activity has stepped up considerably across the region since mid-January 2023. Based on Qfly activity over the past 5 years it is likely that activity will continue to increase through March before flattening out during April and decreasing in May.
NOTE: Fruit fly traps have limited efficacy in measuring Qfly activity throughout the year as fruit fly are not attracted to traps when it’s too cold, too hot, too windy or too wet. Care must be taken in relying too much on trap capture rates. Growers are encouraged to check their crops, whether domestic or commercial, visually – for evidence of fruit fly infestation – in addition to their traps. Traps are perfect for showing where and when Qfly populations are present and where and when they are expanding.
Much of the observed increased activity up to the end of February 2023 existed largely in urban locations offering a variety of host fruits throughout the spring and summer. Now, however, through March and April, Qfly will move out of urban areas, through peri-urban locations and into rural areas (Table 1). Additionally in rural areas, fruit fly populations that just bubble along without being detected will expand rapidly if uncontrolled, in response to the presence and attraction of large volumes of ripening and ripe fruiting crops. Peak Qfly activity occurs in rural locations in late March and throughout April. It is likely to do the same this year.
Weather outlook
The Bureau of Meteorology (BOM) [http://www.bom.gov.au/climate/outlooks – accessed 10 March 2023] suggests the current La Niña weather system will end during autumn 2023 to be replaced by neutral conditions.
As a result, rainfall is likely to decrease to below median levels through March and April and further into winter. These conditions are not favourable to fruit fly survival and proliferation. However, this is countered by the forecast higher than average maximum and minimum daily temperatures for March and April. This is very favourable to Qfly especially those that are at the egg, larva or pupa stage in infested fruit up to mid-April and any surviving adults after that. These will overwinter as adults but will not be captured in fruit fly traps because of low temperatures. They will be the progenitors of the next season of infestations during spring 2023.
Autumn action
Qfly are currently building up in numbers, especially in rural areas where commercial volumes of fruit are ripening or ripe. It is essential to control these flies in commercial orchards, backyard plantings close to orchards, house yards of commercial orchards and feral, abandoned and street trees that produce fruit.
It is essential to reduce fruit fly survival from March into April by ensuring traps are checked and fruit are monitored for infestation. Ensure fruit fly are controlled by netting, crop removal (from both the tree and the ground), and destruction (solarisation, burning, freezing, slashed and spread, etc), whole plant removal (before fruit are ripe), baiting and, if approved, pesticide application.
Autumn control strategies against Qfly apply to managers/ owners of commercial orchards, home gardens and government-owned land.
Goulburn Murray Valley Area Wide Management Fruit Fly Program
For assistance in managing fruit fly, contact the Project Coordinator at the Goulburn Murray Valley Fruit Fly Office by phoning (03) 5871 9222 or email gmvfruitfly@moira.vic.gov.au
This report was produced and supplied by Janren Consulting Pty Ltd for the purpose of the Goulburn Murray Valley Fruit Fly Program. The Goulburn Murray Valley Fruit Fly Area Wide Management Program is supported by the Victorian Government.