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GROWERS URGED TO TAKE A PROACTIVE APPROACH TO WEED RESISTANCE MANAGEMENT
Date added: 21/07/08 |
Growers and advisors should map out areas of fields where black-grass control has been less than adequate this year and start analyzing the reasons why, says ProCam’s Technical Director, Dr. David Ellerton.
If weed resistance is suspected or confirmed through a test, then changes need to be made in future weed control strategies. Dr Ellerton points out that certain groups of chemistry pose a higher risk to resistance than others, namely the ALS inhibitors such as Atlantis and Lexus and the ACCase inhibitors such as Triumph, Topik and Axial.
“Already there are 133 confirmed cases of resistance to Atlantis in 21 counties, with 8 of these being target site and showing absolute resistance. There is confirmed target site resistance to ACCase inhibiting herbicides, too. It is important to realise that once resistance has developed, it doesn’t go away. So it is in within growers control to minimise its further development.
But Dr. Ellerton points out that this has become more challenging as more active ingredients are lost.
“For example the IPU which has been a mainstay product for meadow-grass and broad-leaved weed control as well as doing a reasonable holding job on black-grass is being withdrawn due to its presence in water. Growers can use it until the end of June next year, 2009, but there is probably not sufficient material available to satisfy all growers needs this autumn.”
A second mainstay herbicide trifluralin failed to get Annex 1 listing in Europe and all products containing this active must be sold by distribution by the 20th September 2008, with its use and storage by growers ceasing at the end of March 2009. The loss of these two actives will leave large gaps in the market place, Dr. Ellerton says.
“Chlorotoluron (Lentipur) can be a replacement for IPU in some instances. It gives better rye-grass and wild-oats control, is more persistent and, most importantly, it is less prone to leaching. But it has key varietal restrictions in wheat with Cordiale, Battalion, Duxford, Humber, JB Diego and Xi19 all being exempt from treatment. It is also probably weaker on black-grass.
“Pendimethalin (Stomp and in Crystal) can also, in some situations, substitute for trifluralin. Pendimethalin has a broader weed spectrum and is stronger on cleavers, speedwell, cranes-bill, red dead nettle and fumitory as well as wild-oats, black-grass and annual meadow-grass.
“It is also unaffected by target site resistance and less affected by enhanced metabolism resistance. It has a wider window of use up to Growth Stage 30. Its downsides are the maximum dose rate and the drilling depth,” he says.
According to Dr Ellerton, growers should be planning to use mixtures or sequences of herbicides with different modes of action in order to reduce resistance risks. But they should also be actively using cultural control, such as delayed drilling, more spring cropping and ploughing, in order to reduce weed populations prior to herbicide applications.
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