Bug briefing | 4 - 24 August

 

Bug Briefing is an overview of some 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.

 

Armyworm

Native species of armyworm have been detected in several paddocks around Marnoo and St. Arnaud in North Central Victoria. It was noted that the armyworm detected were a range of sizes indicating that the populations arose from multiple moth flights. In one paddock, the armyworm were patchily distributed and in some areas in very high numbers. Dark forms of the larvae were also spotted crossing a gravel road en masse. This ‘marching’ behaviour occurs when armyworm become very stressed when their food supply has been depleted or they are overcrowded.

Near Elmore, very high numbers were detected in a wheat paddock under the wheat stubble. Chewing symptoms on leaves were evident.

 

A native species of armyworm in high numbers in a pasture paddock. Image: Rob Fox

 

Brown pasture looper

Large brown pasture looper larvae were found causing significant feeding damage to a canola crop north of Albury in the Murry region of NSW.

Very high numbers of brown pasture looper larvae were also found in pasture paddocks near Ararat in the Victorian Wimmera and also near Marnoo in North Central Victoria, where they were spotted eating capeweed and Erodium.

The larvae have also been spotted in cereals where they aren’t expected to be problematic (they prefer broadleaf species).

Very high number of brown pasture looper larvae were found eating the broadleaf weed component of a pasture. Image: Rob Fox

 

Pasture day moth

Near Echuca in the North Central Victoria, large pasture day moth larvae were spotted excavating vertical tunnels in the soil (they would have eventually crawled down and pupated).

Video: James Challis

 

Russian wheat aphid

Very low levels of Russian wheat aphid were detected west of Hopetoun in the Victorian Mallee. In the same region closer to Ouyen and Manangatang, the aphids have also been reported in several cereal paddocks with the biggest numbers in crops that had not received a seed treatment, although aphids had now also started to appear in those that had been treated.

 

Beneficials: hoverflies and lacewings

With early flowering of canola, very high numbers of beneficial hoverflies have been spotted during paddock inspections.

In a paddock of barley, brown lacewing larvae were spotted hunting around curled leaves caused by Russian wheat aphid.

 

Acknowledgements

Thanks to the following for providing field observations: Rob Fox (Fox and Miles), Tom Batters (Agrivision), Greg Toomey (Nutrien Ag), Sheree Hamson (Elders), Andrew James (Dogshun Medlin), Claudia Higgens (Western Ag), James Challis (Nutrien Ag), Bruce Larcombe (Larcombe Agronomy), Hayden Lunn (@lmkmills1), Greg Dearman, Andrew McMahen (Nutrien Ag).

 

Header illustration: Elia Pirtle, cesar