PestFacts south-eastern The evolution of resistance to neonicotinoids further limits the options for control of green peach aphid and underlines the need for sound management strategies to ensure long-term access to available chemistries.
Resistance to neonicotinoid insecticides has for the first time been confirmed in Australian populations of green peach aphid (Myzus persicae).
This discovery means that green peach aphid is known to have resistance to four different chemical groups – synthetic pyrethroids (e.g. alpha-cypermethrin), organophosphates (e.g. dimethoate), carbamates (e.g. pirimicarb) and now, neonicotinoids.
Neonicotinoids, such as imidacloprid, are applied as seed treatments in the grains industry and have become common place in canola pest management across Australia.
About green peach aphid
Green peach aphid has a wide host range, including oilseeds, lupins, pulse crops and some broadleaf pastures.
Non-crop hosts include capeweed, marshmallow, wild radish, wild turnip, Lincoln weed and other cruciferous weeds.
Green peach aphid is an important vector of a number of plant viruses including turnip yellows virus (TuYV)(syn. beet western yellows virus), cauliflower mosaic virus (CaMV), turnip mosaic virus (TuMV) and cucumber mosaic virus (CMV), all of which damage canola.
Insecticide resistance and green peach aphid
Resistance to neonicotinoids has been detected in a handful of green peach aphid populations across Australia.
This work has been led by cesar researchers Dr Siobhan de Little and Dr Paul Umina, in collaboration with CSIRO. cesar has been conducting research into insecticide resistance for the last decade.
In the last 2 years, green peach aphid has been collected from horticultural and grain crops across Australia, with resistance detected in several populations from Queensland, South Australia and Western Australia.
Currently, green peach aphid populations within Australia have target-site resistance to pyrethroids and carbamates, where a genetic mutation in the aphid causes a high level of resistance to these chemicals. As a result, these insecticides are completely ineffective, even when applied at the full field rates.
The mechanism underlying neonicotinoid resistance has been identified as metabolic; the aphids are able to detoxify the insecticide somewhat, resulting in low to moderate levels of resistance.
So, what does this mean for canola seed treatments registered against aphids?
Gaucho®, Cruiser® Opti and Poncho® Plus all contain neonicotinoid insecticides.
Although difficult to predict, these seed treatments should still offer protection to canola seedlings from resistant populations of green peach aphid due to the low levels of resistance in Australia.
However, the length of protection offered by seed treatments may be reduced. Research will be needed to explore this further.
Our advice
The presence of resistance to neonicotinoids demonstrates current management practices, such as regular application of chemicals from the same IRAC mode of action group, are not sustainable.
If management practices remain the same, it is likely that imidacloprid and other neonicotinoids will become ineffective due to ongoing resistance evolution and spread.
There is a second mechanism conferring neonicotinoid resistance in green peach aphid, which leads to a very high level of resistance, and complete field failures. To date, this mechanism, which is found overseas, has not been detected in Australia.
To reduce the risk of resistance to any insecticide group, it is important to rotate insecticides with different modes of action, avoid the use of broad-spectrum insecticides, and apply appropriate insecticides only after careful monitoring and correct identification of species.
Transform®, a sulfoxaflor foliar insecticide, remains an effective means to control green peach aphid in canola crops, and should be used judiciously.
Growers and advisors are encouraged to download, and follow, the Green Peach Aphid Resistance Management Strategy to minimise the further development of insecticide resistance.
Cover image: Photo by Julia Severi, Cesar Australia
