Caterpillars continue to cause concern
Weed web moth and cabbage centre grubs
- Bruce Rock
Technical Officer Salzar Rahman (DPIRD) has found cabbage centre grubs (Hellula sp.) causing damage to his canola trial near Beverley.
Technical Officer Amber Balfour-Cunningham (DPIRD) recently found cabbage centre grub caterpillars on roadside wild radish near Quairading and Kweda while conducting green bridge surveillance.
Research Scientist Christiaan Valentine (DPIRD) has found small cabbage centre grubs (8-15mm long) in wild radish and roadside canola near Highbury, Bruce Rock and east of Wagin whilst surveying for diamondback moth larvae. This indicates that the moths, which are a pest of broadleaved plants such as canola, have been flying in the area and laying eggs on available plants.
Weed web moth and cabbage centre grubs are in the same family (Crambidae) and can look very similar, especially the brown banding down the body of caterpillars. They also both produce webbing amongst the leaf tissue. The most distinguishing characteristic of weed web moth is the dark circles or spots along the body (see image below).
For more information about these pests refer to cesar’s recent PestFacts south-eastern newsletter articles Cabbage centre grubs in establishing canola and forage brassicas and High numbers of web-spinning moth larvae are feeding on broadleaf plants.
Brown pasture looper
Hilary Wittwer (Planfarm) has found a number of caterpillar species in a paddock near Williams which was sprayed out with herbicide to control weeds. One unknown type was black and hairy and unlikely to be a crop pest, while another was the brown pasture looper, a known pest of broadleaved crops such as canola and pulses.
Brown pasture looper caterpillars are slender, grey or brown in colour with black and cream stripes and they move with a characteristic looping motion.
Brown pasture loopers have one generation per year and are likely to starve to death within two weeks if no host plants are available. For more information see DPIRD's Diagnosing brown pasture looper page.
Managing caterpillar pests
If you are considering chemical control for caterpillar pests refer to DPIRD’s 2020 Autumn winter insecticide spray guide.
The PestFax team wants to know what invertebrate insects you are finding in your crops and pastures, whether it is a pest, beneficial or unknown. We even want reports of the usual insects that are seen every season. Please send your reports or identification requests in via the PestFax Reporter app.
For more information on monitoring insects in emerging crops refer to;
- DPIRD’s Monitoring insects and other crop pests page
- GRDC’s Monitoring for insects in canola. Part 1 video
- GRDC’s updated I SPY manual.
Article author: Dusty Severtson (DPIRD Northam) and Cindy Webster (DPIRD Narrogin).