Northern growers and agronomists will be able to better manage the economic cost of controlling midge in sorghum crops this season with the help of a new online threshold calculator, developed by the Department of Agriculture Fisheries and Forestry (DAFF) entomology team.
Midge on a plant (photo courtesy of Ken Laws)
The calculator helps determine the economics of applying an insecticide, taking into account the midge resistance (MR) rating of the variety, row spacing, number of midge in the field as determined by the grower or consultant, crop value, cost of control and residual life of the chosen insecticide.The Grains Research and Development Corporation (GRDC) recently released the Sorghum Midge Spray Calculator factsheet outlining how growers can utilise the new tool to make more informed and precise spray decisions based on individual growing parameters.
DAFF research scientist Tracey Shatte operates the GRDC-supported Sorghum Midge Tested Scheme at Hermitage Research Facility, Warwick, and said the online calculator would ultimately help growers maximise crop profitability by strategically managing insecticide control costs and protecting yield.
“By better planning and reducing insecticide applications, growers can save money and also spare beneficial insects, which can improve outcomes in the whole cropping system,” Ms Shatte said.
Sorghum midge (Stenodiplosis sorghicola) is one of the most damaging of all grain sorghum pests and has been estimated to cost the Australian industry $10-$15 million a year in residual losses and uncontrolled damage.
One of the most important genetic developments in grain sorghum in the past 30 years has been the introduction of midge resistance into hybrids and since 1993 the Sorghum Midge Tested Scheme has enabled growers to select sorghum hybrids with official MR ratings.
However Ms Shatte warned that MR ratings did not guarantee immunity from midge damage, particularly when midge populations were high.
“A hybrid with an MR rating of 5 could lose over 20pc of its yield under high midge pressure so it’s important that the MR rating is used as a tool for managing crops rather than a guarantee of preventing midge damage,” she said.
“As the sorghum season approaches, it’s extremely important that growers are aware of the management tools available to them as sorghum midge populations can build up from early spring because of their ability to breed in Johnson grass.
“In warm and humid conditions, a new generation of midge is produced in 2-3 weeks. So if a sorghum crop flowers during late-summer, midge populations can already be at potentially devastating levels for the crops.”
The calculator can also be used off-line, so growers can take advantage of its flexibility and use it in the paddock on mobile devices.
The Sorghum Midge Spray Calculator factsheet can be downloaded at www.grdc.com.au/GRDC-FS-SorghumMidgeCalculator
The Economic Threshold Calculator is available at DAFF’s blog The Beat Sheet http://thebeatsheet.com.au/sampling-2/
Tracey Shatte, Research Scientist, DAFF
07 4660 3628
Sarah Jeffrey, Senior Consultant, Cox Inall Communications
07 4993 7135, 0418 152859
GRDC Project Code