A BURROWING pest responsible for massive crop losses from the Liverpool Plains up to Queensland's Darling Downs is in the sights of the Grains Research and Development Corporation (GRDC).
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Damage from scarab beetles is affecting both summer crops and winter cereals including sorghum, maize, sunflower, mungbean and wheat, and the GRDC is helping to fund research it hopes will find a solution.
While reports of scarab damage have tended to be sporadic and associated with wetter seasons, in certain areas, persistently affected paddocks have suffered up to 80 per cent loss in sorghum crops, prompting on-going research into a variety of potential control methods.
Scarabs feed on roots, impacting on plant growth and ability to tolerate moisture stress, which is visible as slowed crop growth, plant death (often in patches), delayed maturing and lodging.
Scarabs generally have a one to two-year lifecycle which can be longer if growing conditions are unsuitable such as if it is too dry or food sources are inadequate.
This means larvae can be present in fields for 12 months of the year.
Recent in-field trials have focussed on cultivation, comparing the impact of a single offset disc and chisel plough on scarab larvae densities, as well as insecticide treatments at sowing, both in-furrow treatments and seed treatments.
Dr Melina Miles, principal entomologist with the Queensland Department of Agriculture and Fisheries (DAF), said both the disc and chisel plough cultivation trials resulted in a significant reduction in larvae numbers but also resulted in a full disturbance of the soil surface and correspondingly high reductions in soil moisture.
"The impact of cultivation on soil moisture is a major impediment to the potential uptake of cultivation to manage high density infestations," Dr Miles said.
"However it may be possible to be more targeted with cultivation and achieve the same outcome. Examination of the distribution of larvae across the plant row and inter-row shows a concentration of larvae on the plant row in the majority of fields.
Dr Miles said trials assessing the efficacy of in-furrow and seed treatments had also been undertaken given there was little information on the impact of these treatments on the scarab larvae.
She said although preliminary results suggested that insecticide treatments at sowing could potentially provide some crop protection, it was also probable that the insecticides would deter larvae from the zone in which they were active but as roots grew out of the treated zone they could then be damaged by larvae.
Dr Miles encouraged growers and advisors to monitor for scarab larvae during the growing season and if larvae were found, to contact her at DAF Toowoomba on 13 25 23 or melina.miles@daf.qld.gov.au
