Testing times for herbicide-resistant weeds
Author: Sharon Watt | Date: 20 May 2016
Grain growers and their advisers are being encouraged to consider testing the herbicide resistance status of weeds growing on farms in the southern cropping region to help inform their weed management strategies.
Screening weeds for resistance provides valuable information on the effectiveness of herbicides on target weeds, potentially preventing the wasteful use of ineffective herbicides and reducing the spread of herbicide resistance.
Grains Research and Development Corporation (GRDC) Southern Regional Panel member Kate Wilson says testing can be conducted either by using test strips in the paddock or by sending plants or seeds to a commercial testing service.
Ms Wilson, an agronomic consultant based at Hopetoun in Victoria’s southern Mallee, says that while paddock tests can provide useful information, they can sometimes be difficult to interpret due to the variability of paddock conditions.
“Commercial testing – of either weed seed or live plants – provides a reliable reading and services are able to test different herbicides at different rates,” Ms Wilson said.
Testing of live weed seedlings through the Weed Resistance Quick-Test can be undertaken at this time of the year.
Any paddock where herbicide resistance is suspected as the cause of a spray failure can be tested.
“Priority should be given to testing weeds in high risk paddocks where there is a long history of herbicide use and herbicide survivors have been allowed to set seed,” Ms Wilson said.
For each herbicide to be tested through Quick-Test, the service requires about 50 plants if they are small with few tillers, or 20 larger later-stage tillering plants.
Plants can be sampled either before a herbicide application or after herbicides have been applied and weeds aren’t killed.
Quick-Test is offered through Plant Science Consulting. The test takes about four weeks to complete.
Ms Wilson said herbicide resistance was a significant and costly issue for grain growers in the southern region and the broader grains industry.
“Weeds which survive herbicide application produce viable seed which can later germinate, resulting in another generation of herbicide-resistant weeds.
“This is why it is so important to employ an integrated weed management strategy comprising a double knock of herbicides, mixing and rotating chemicals, using competitive crops, stopping seed set, and harvest weed seed control.”
Information on herbicide resistance and weed management is also available at www.weedsmart.org.au.
Kate Wilson, GRDC Southern Panel
ContactSharon Watt, Porter Novelli