PestFacts Issue 10, 2018
Native budworm (), Helicoverpa punctigera, larval numbers in canola are increasing on the west coast of the Eyre Peninsula and have caused considerable damage around Pinnaroo in the South Australian Mallee. The moth trapping network detected large flights (> 400 moths) on the 9th October at Mannanarie. Where pulse crops are within a few weeks of desiccation and/or harvest, recent flights are likely to be too late for any resulting larvae to develop to a size that can cause significant damage. Crops remaining green for several days after windrowing are still susceptible to attack from large larvae (4th-5th instar, > 30-40mm in length).
There have been several reports recently of budworm in barely on the Southern York Peninsula (5-10 larvae per sweep average), and cereals on Kangaroo Island. Identity of the species hasn’t yet been confirmed, but are likely to be the cotton bollworm (), Helicoverpa armigera, or possibly the lesser budworm, Heliothis punctifera, as they were observed in cereals.
We are now wrapping up the Helicoverpa trapping program for this year. Many thanks to our volunteer trappers for your effort and participation: Andy Bates, Chris Davey, Adam Hancock, Ben Farmer, Troy Maitland, Sarah Meyer, Nigel Myers, George Pedler, Steve Richmond, and Iain Todd.
Diamondback moth (), Plutella xylostella, larvae activity on canola has been increasing steadily for the past month on the lower Eyre Peninsula. Large numbers of larvae were detected west of Yeelanna and at Karkoo, and have reached treatment threshold guidelines (> 100-200 larvae per 10 sweeps) at Mt Hope and Yeelanna. Canola crops that are due for windrowing are now within the two-week withholding period for applications of Affirm (windrowing is considered harvest).
Cabbage aphid (), Brevicoryne brassicae, numbers are increasing on canola around Mannanarie, and canola has been sprayed around Cummins and Naracoorte. Lower Eyre Peninsula had considerable rainfall (20-40mm) recently, which has lowered aphid numbers. However, large numbers of aphids are still being observed on the upper Eyre Peninsula, including cowpea aphid (), Aphis craccivora, in pasture paddocks. Farmers have detected sheep with symptoms of photo-sensitisation (skin inflammation, wounds and scabbing) feeding in these pastures. Whilst the link is not clear, cowpea aphids were associated with livestock photosensitisation last season (see PestFacts Issue 10, 2017).
A barley crop in the Naracoorte area has significant numbers of oat aphid (), Rhopalosiphum padi, (50-100 aphids per tiller on 100% of tillers). Green peach aphid () (GPA), Myzus persicae, has been observed on the lower leaves of canola plants around Cummins, but this aphid is typically of little concern in spring. However emerging brassicas, GPA has been reported damaging in the South East, particularly around Naracoorte.
It’s been a quiet year for the Russian wheat aphid (RWA), Diuraphis noxia, which may reflect the dry summer and lack of green bridge in early autumn. However, we have recently received multiple reports of minor infestations from Eyre Peninsula, Roseworthy, Loxton and other areas, where some plants in paddocks show symptoms (mainly below thresholds). RWA is on the move with rising temperatures. Very late sown cereals and regrowth after hay-cuts will be sensitive to RWA colonisation so keep an eye open for symptoms. Please report any sightings.
As part of a GRDC RWA project SARDI will be sampling for green bridge populations in the coming weeks across South Australia. If you do see some strange person vacuuming a roadside or a paddock, and inspecting grasses….it’s us!
Cutworm (), Agrotis sp., is damaging emerging sorghum around Cleve. Large numbers of armyworm () were detected on the upper western side of the Eyre Peninsula, with some areas above or near treatment thresholds (1-3 larvae per m2). There has been a recent increase in Etiella (), Etiella behrii, numbers (5-10 per trap) on lentils near Cummins and Yeelanna, where additional treatments were required. In Murbko on the 7th Oct, recently hatched Australian plague locust (not confirmed) were detected moving across the ground, after a light rainfall event. Overall locust populations are low this spring, with only isolated activity.
Sources of all reports: Maarten Van Helden (SARDI), Steve Richmond (Landmark Jamestown), Nigel Myers (Cummins Ag), Adam Hancock (Elders), Lou Flohr (Byrne Ag Landmark), Cherylynn Dreckow (Elders Cleve), Clint McEvoy (Landmark Streaky Bay), Tom McKinnonn (Landmark Naracoorte), James Chard (Growers Suppliers YP), Craig Wissell (Team Wiss Agronomy).