A joint research project is working with a tiny midge as a biological control for the declared pest skeleton weed in Western Australia.
Skeleton weed is a fast-spreading invasive weed that can cause grain crop yield losses and increase grower costs.
The Department of Primary Industries and Regional Development (DPIRD) and Australia’s national science agency CSIRO are monitoring the establishment of the skeleton weed gall midge, Cystiphora schmidti, in WA’s grainbelt.
DPIRD project officer Kate Detchon said the gall midge had been used in eastern Australia since the 1970s, it only affected skeleton weed and did not attack other plants.
“Using a natural, host-specific enemy like this offers another complementary control method against skeleton weed, which is a vigorous and problematic weed,” she said.
“Biocontrol will not replace chemical methods for eradication but can add to the integrated weed management toolkit.”
The gall midge was released in spring last year into skeleton weed infested sites at Narembeen and Dandaragan.
Ms Detchon said results had been mixed, with heavy grazing and protracted hot conditions impacting the gall midge’s survival at some sites.
“The best performing sites have been at Narembeen, where we are now seeing gall midge numbers that are high enough to have a negative impact on skeleton weed plants,” Ms Detchon said.
“These results are encouraging as we didn’t anticipate seeing signs of impact this soon.
“Heavily affected plants stand out in the field due to masses of dark dead leaves. Some plants are showing impact up to 50 metres from the initial release site.”
CSIRO experimental scientist Michael Davy said the insects were brought to WA, in accordance with relevant biosecurity regulations, to establish a local breeding colony for further releases.
“These beneficial insects are natural weed warriors,” Mr Davy said. “They feed on skeleton weed and will spread to tackle this weed across the landscape.”
Gall midge has a life cycle of several weeks, with adults emerging primarily in spring and summer when skeleton weed is most abundant.
Females lay between 60 to 180 eggs each on leaves and stems of the skeleton weed plant. The larvae hatch and feed within the plant, forming purple and green galls.
When galls are abundant, infested leaves and stems die off, which can stunt the plant’s growth and reduce flowering, seed production and root reserves.
The introduction of any biological control agent is highly regulated to ensure there are no adverse impacts on the environment.
The research is part of the broader Skeleton Weed Program, which is supported through the grower-funded Grains, Seeds and Hay Industry Funding Scheme.
Under the State’s Biosecurity and Agriculture Management Act, skeleton weed is declared as an eradication target for the whole state, except Narembeen and Yilgarn shires where it is under a management declaration.
More information on skeleton weed in WA is available from the DPIRD website.
Print this page
