The Rutherglen bug has been an increasingly frequent and problematic pest for grain growers in Queensland and NSW during the past 10 years, but recently observed behaviours are causing further concerns.
Queensland Department of Agriculture and Fisheries senior entomologist Dr Melina Miles said during the past four years agronomists had observed that large numbers of the bug, which breeds in canola, have caused damage to establishing summer crops.
This type of damage is in addition to the significant yield losses that can be attributed to the adult bugs in sorghum and sunflowers during grain fill.
‘‘Our observation of this damage in seedling summer crops is relatively new,’’ Dr Miles said.
‘‘To date very little research has been focused on the phenomenon of RGB movement from canola stubble to damage an establishing summer crop.
‘‘DAF entomologists have done some preliminary work, which has provided some insight, but there needs to be further research in this area,’’ Dr Miles said.
Rutherglen bug nymphs at all developmental stages, and adults, typically move en masse from canola stubble as it dries down in October-November, with the movement occurring in all directions.
Dr Miles said it appeared to be an exodus rather than direct movement towards summer crops.
‘‘In southern Australia, the same movement occurs and is of little consequence as there are no summer crops,’’ she said.
The absence of effective, long residual products that can be applied to bare earth between canola stubble and summer crops is a major constraint in having a simple management option.
‘‘The three key approaches we are researching this year include preventing the build-up of RGB, effective barriers to the movement from stubble to summer crop and reducing RGB populations in summer crop,’’ she said.
■For more tips from Dr Miles on how to identify and manage RGB check out this GRDC Know More video at: https://youtube/BnGDHhNmdIE