Canola attack spurs resistance campaign
In Australia, the green peach aphid (GPA) primarily attacks canola by sucking sap from leaves and flower buds. When populations are large, the crop’s entire foliage may be covered, resulting in retarded growth. GPA can transmit more than 100 plant viruses, such as beet western yellows virus (BWYV) and cucumber mosaic virus (CMV).
This season, a high incidence of BWYV, causing severe crop damage, occurred in canola crops in large areas of South Australia and Victoria. Unusually high infections were also found in parts of New South Wales.
This follows widespread infestations of GPA, the principal vector of BWYV, in canola crops during autumn and early winter.
Despite the known increase in insecticide resistance among GPA populations, the use of chemicals to target GPA continues to increase.
Recent resistance mapping led by cesar has found that GPA populations across Australia have resistance to multiple insecticide groups. Resistance to carbamates (for example, pirimicarb) and pyrethroids is now widespread. Moderate levels of resistance to organophosphates have also been observed. In response, the National Insecticide Resistance Management (NIRM) working group of the Grains Pest Advisory Committee has developed the first resistance management strategy for GPA in grains. This strategy aims to conserve the effectiveness of the limited insecticide options for this pest. To do this we need to minimise the selection pressure for resistance to the same insecticide group across consecutive GPA generations. As with other pest (and weed) resistance management strategies, the rotation of different groups of chemicals is critical.
Regional differences in resistance across Australia have required regionally relevant strategies. For example, pirimicarb is not recommended for GPA control in canola crops in Western Australia, Queensland and South Australia due to the widespread levels of resistance to this chemical in these states.
In addition to chemical rotation, the success of this strategy will depend on the use of economic thresholds and implementation of monitoring programs for pest (and beneficial insect) populations before making spray decisions.
Canola and pulse growers across Australia are encouraged to become familiar with, and follow, the recommendations of the new resistance management strategy.
The South Australian Grain Industry Trust (SAGIT) has provided $40,000 in emergency funding to support research into beet western yellows virus. The virus is transported by green peach aphids, which have thrived in recent warm and humid weather.
It is estimated that at least 7000 hectares of canola crops have been affected by the virus in South Australia’s lower and mid-north regions and the state’s Mallee. There have also been instances of the virus reported in crops in Victoria and southern New South Wales.
SAGIT chair Jim Heaslip says the trust provided the funding because it considered the virus an emergency situation for the canola industry in SA.
“The state has about 285,000 hectares of canola and we produce about 440,000 tonnes of canola a year. So a significant outbreak like this is going to have a significant economic impact on a lot of SA growers,” Mr Heaslip says.
Dr Paul Umina
03 9349 4723
For related GRDC resources visit the Ground Cover Direct segment in this issue of Ground Cover.
This strategy has the endorsement of CropLife Australia. It can be downloaded at: http://ipmguidelinesforgrains.com.au/ipm-information/resistance-management-strategies
GRDC Project Code UM00048, CES00001
Region National, North, South, West