Green peach aphid

* Green peach numbers have continued to remain low in all regions. * A brief update on the progress of the resistance testing is provided.

 

Green peach aphid (GPA - Myzus persicae) is a widely recognised pest of grains and horticultural crops. It came into particular prominence this year as the vector of Beet Western Yellows Virus, which severely impacted many canola crops across south-eastern Australia. To add to concerns, GPA is resistant to many groups of pesticides. Together with CSIRO, cesar is researching the resistance issues in GPA and has recently undertaken extensive resistance testing using DNA-based methods. A brief update on this work follows.

DNA resistance testing is ongoing; to date we have tested 45 populations. Results continue to indicate resistance to the three chemical groups tested: synthetic pyrethroids (e.g. alpha-cypermethrin), organophosphates (e.g. dimethoate) and carbamates (e.g. pirimicarb). You can view updated resistance maps for SA, Victoria and NSW by clicking here.

GPA reports and samples have tapered off dramatically – we have received no new samples since early September. Even then, many samples received in September, particularly from lentils, were the potato aphid (Macrosiphum euphorbiae) rather than GPA. This highlights the difficulty in distinguishing many crop aphids. In the event that GPA do become evident in a crop, we still seek samples for testing. Contact Siobhan de Little (P: 03 9349 4723; E: sdelittle@cesaraustralia.com)

Despite the high resistance levels to organophosphates across all regions, in some cases, growers have successfully used high levels of dimethoate (i.e. 800ml/ha) to control GPA populations. Conversely, a similar rate of dimethoate has been reported to offer little control against a GPA population, again in an area where organophosphate resistance was identified. This further serves to illustrate the complexity of this resistance mechanism, and that test strip spraying and working on a case-by case scenario is currently the most effective way to manage resistance in this chemical group.

Thanks to everyone who spent considerable time and energy collecting aphids and filling in surveys. Through your help, we have built a comprehensive picture of insecticide resistance across south-eastern Australia. This will serve to further aid in the management and control of GPA into the future. Further information about resistance in GPA, including management advice, can be found here.

The resistance testing work is being undertaken by Dr Siobhan de Little and Anthony van Rooyen, cesar.