Western Australian growers considering whether to control native budworm can be guided by monitoring crops and using a table which calculates the economic threshold for spraying the late-season pest.
Native budworm caterpillars (Helicoverpa punctigera) – which affect grain quality and yield – have recently been found in WA canola and pulse crops, including lupins, in the northern and eastern grainbelt.
Past research supported by the Grains Research and Development Corporation (GRDC) has helped the Department of Agriculture and Food (DAFWA) refine native budworm monitoring and control guidelines.
DAFWA entomologist Svetlana Micic said growers should first sample crops thoroughly for the insects before assessing whether to spray them.
“From the start of flowering, monitor crops for insect pests once a fortnight,” she said.
“If crops are stressed, check them weekly as pests can build up rapidly in warm conditions.”
Ms Micic said sampling should be conducted with a sweep net, and 10 sweeps of the crop should be carried out at five to 10 different locations within the paddock.
“After completing the set of sweeps, counts should be averaged to give an overall estimate of abundance,” she said.
“Growers can then enter these sample figures, along with grain prices and control costs, into formulas provided in a budworm economic threshold table developed by DAFWA.”
The table and other management information is located on the DAFWA website www.agric.wa.gov.au, under Management and economic thresholds for native budworm, which can be found by searching ‘budworm’.
“If control is required, one well-timed spray with a synthetic pyrethroid should provide good control of larvae and prevent reinfestation for up to six weeks,” Ms Micic said.
“However, growers should note that while synthetic pyrethroid insectides are very effective, their broad spectrum activity impacts negatively on beneficial insects.”
Ms Micic said late season hatchings were often too late to cause economic damage, but native budworm larvae could still damage canola after windrowing if many pods were still green.
“Be aware of insecticide withholding periods close to harvest and remember that windrowing is classified as harvest,” she said.
More information and resources about budworm can be found on the Budworm in Western Australia page of this website.
Photo Caption: Growers should first sample crops for native budworm before assessing whether to spray them.
Svetlana Micic, DAFWA
08 9892 8591, 0427 772 051
Natalie Lee, Cox Inall Communications
08 9864 2034, 0427 189 827
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