Green peach aphid update

While populations of green peach aphid have been reported recently, their activity and the risk of virus transmission has decreased with the onset of winter.

Green peach aphid nymphs and adults (Source: cesar).

 

We continue to receive reports of green peach aphid (Myzus persicae, GPA) in canola from the Victorian Mallee, Wimmera and North East, and the NSW Riverina. While most of these have been low to moderate populations, there has been some concern about potential beet western yellows virus (BWYV, syn. Turnip yellow virus) symptoms in a number of crops hosting GPA. Suspect samples have been sent away for laboratory testing, and we will keep you posted if we hear of any positive results. Remember that BWYV symptoms can resemble nutrient deficiencies, herbicide damage and physiological stress.

Canola is most susceptible to BWYV up to the rosette stage, when infection can lead to high yield losses. Yield consequences decrease with infection of BWYV at later stages of crop development, however canola can remain susceptible to yield losses until approximately the mid-podding stage. Infection after this stage typically results in minimal yield loss but oil quality can still be affected. BWYV can be transmitted by relatively few aphids feeding on plants, and symptoms may not present themselves for up to five weeks post infection. For more information on BWYV and GPA click here.

GPA activity and the risk of virus transmission decline with the increasingly cold conditions. Insecticides should only be applied when absolutely necessary. There are several insecticides registered against GPA. However, many populations have developed resistance to a range of chemical groups. In Australia, GPA are resistant to synthetic pyrethroids, carbamates (e.g. pirimicarb) and organophosphates. Recent research by cesar and CSIRO has also identified low levels of resistance to neonicotinoids (e.g. imidacloprid) in some populations.

To reduce the risk of insecticide resistance, rotate insecticides from different chemical groups, avoid the use of broad-spectrum insecticides, and apply appropriate insecticides only after careful monitoring and correct identification of species. Growers and advisors are encouraged to download, and follow, the GPA Resistance Management Strategy to minimise the further development of resistance.

 

Field reports

Lincoln Harris – Elders (Riverina, NSW)

Barry Haskins – Ag Grow Agronomy and Research Pty Ltd (Riverina, NSW)

Erin Johns – AGRIvision consultants (Wimmera, VIC)

Bruce Larcombe – Larcombe Agronomy (North East, VIC)

Kurt Linbeck – NSW DPI (Riverina, NSW)

John Mckenzie – Landmark (North East, VIC)

Rick Rundell-Gordon – Grounded Agronomy (Mallee, VIC)

Greg Sefton – Sefton Agronomics (Riverina, NSW)