Bug Briefing: 16 – 29 June 2020

 

 

 

Bug Briefing is an overview of recent invertebrate reports sent to PestFacts south-eastern, providing a snapshot of pest and beneficial activity in broadacre crops and pastures in Victoria and southern NSW.

 

Brown pasture looper

High numbers of tiny loopers were reported grazing on lucerne, clover, canola, and some cereals around Junee, Riverina NSW. We received a sample from the region, and they were identified as young brown pasture looper larvae (which aren’t as distinctive as older, larger larvae).

Older brown pasture looper larvae (6-8 m²) were reported causing concerning feeding damage in a paddock of seedling canola in Bailliang, 30 km north of Geelong.

They were also spotted in a dryland lucerne paddock around Boort, North Central Victoria, mainly in one patch grazing on lucerne plants and capeweed.

 

Armyworm

Low numbers of final instar native armyworm larvae (Mythimna or Persectania sp.) were found in young barley between Forbes and Grenfell, Central West NSW. Native armyworms are also suspected to be behind chewing damage in a young wheat crop near Horsham, Victorian Wimmera. Current populations present won’t be those that pose a ‘headlopping’ risk as they will pupate and likely migrate away from the paddock well before the crop starts to dry off.

Native armyworm larvae have also been noticed near broadleaf crops near Boort, North Central Victoria. Armyworm are not a risk to winter broadleaf crops in the south where armyworm species prefer cereals and grasses. They are likely present because of retained cereal stubble, a known site of armyworm moth egg laying.

 

Pasture day moth

The larvae of the sporadic pasture day moth (Apina callisto) caused minor feeding damage in two patches in a paddock of young wheat around Boort, North Central Victoria.

Further west near Wycheproof larvae were spotted chewing a young wheat crop down to near ground level in some patches.

 

Lucerne flea (and other springtails)

Shot holes and windowing damage were seen in an establishing faba bean crop northwest of St. Arnaud, North Central Victoria. Lucerne flea (Sminthurus viridis) were present in some areas of the paddock and were caught feeding on the underside of leaves.

Nearby around Boort, lucerne flea are also responsible for some windowing damage in a two-leaf stage canola crop.

Remember lucerne flea is really the only springtail of concern in broadacre crops during winter. Other springtails have been spotted in high numbers, but these are very likely to be detritivores and are not a cause for concern.

 

Lucerne flea feeding on the underside of faba bean leaves. Image: Rob Fox

 

Other springtails spotted in crops that are most likely feeding on decaying organic matter. Images: Mark Breust; Heath Griffiths; Daniel Andrews

 

Aphids

Russian wheat aphid (Diuraphis noxia) continues to be sighted in wheat and barley growing regions of south-eastern Australia with reports ranging from just a few plants and localised hot spots, to some cases of moderate and above threshold incidences.

Other aphids have also been spotted in cereal crops, including corn aphid (Rhopalosiphum maidis) in the Trundle region of Central West NSW, and oat aphid (Rhopalosiphum padi) around Newbridge, North Central Victoria.

Cowpea aphid (Aphis craccivora) hot spots have been reported in vetch around Birchip, Victorian Mallee.

A mixed population of turnip aphid (Lipaphis pseudobrassicae) (mostly) and green peach aphid (Myzus persicae) was reported in less than 5% of canola plants in a paddock near Hopetoun, Victorian Mallee.

Voracious beneficial predators such as ladybird beetle and lacewing larvae have also been noticed alongside aphid populations in some cases.

 

Blue oat mites

Blue oat mites (Penthaleus sp.) were reported causing significant silvering and yellowing in young canola around Birchip, Victorian Mallee. The damage was found in very large patches (e.g. 50 m x 20 m).

Similarly, in North Central Victoria near Donald, basketball court size blue oat mite hot spots were found in young canola. Hundreds of mites were spotted near shrivelled up and dying plants.

For assistance with mite identification, see our Crop and Pasture Mite Identification video.

 

‘Worms’

High numbers of pot worms (also known as Enchytraeids) have and continue to be spotted in soils this autumn and winter. These small (5 – 10 mm) translucent wrigglers with no head or legs can be quite abundant in soils, and it can be tempting to point the finger at them if found in the vicinity of crop damage. But pot worms are decomposers, not pests, and are not a cause for concern.

Don’t be concerned about these white worms in your soils, they are pot worms and are not crop pests. Image: cesar

 

Acknowledgments

Thanks to the following for providing field observations: Angus Knight (Riverina Co-op), Rob Fox (Fox and Miles), Rhiannan McPhee (Swan Hill Chemicals), Matt Bissett (Agrivision), Phil Gray (Agnvet), Kelly Angel (Birchip Cropping Group), Sam Schulz (Elders), and Craig Sharam (Elders), Mark Breust (Delta Ag) and Elliot Lade, Justin Whittakers, Kris Dixon, Heath Griffiths, Daniel Andrews and Alistair Ferrier (Nutrien Ag Solutions).

 

Header illustration by Elia Pirtle, cesar