MINUTES OF WRAG STEERING GROUP MEETING
TUESDAY 8 MAY 2007, at BAYER, CAMBRIDGE
Members present (8+2): James Clarke (Chairman), Stephen Moss (Secretary), Chris Rundle (PSD), Mark Ballingall (SAC), Gordon Anderson-Taylor (Bayer), Steve Cranwell (DuPont), Jason Tatnell (Syngenta), Clare Bend (Masstock).
By invitation: Anne Thompson (Dow) and Iain Ford (BASF)
WRAG’s web address:
1.Apologies for absence. None.
2.The minutes of the last Steering Group meeting (24 November 2006) were approved. These can be viewed on the WRAG website.
Matters arising.
Anne Thompson said that reforming a European HRAC was being considered, as it was accepted that HRAC had largely a North American focus at present. HRAC has just company representation whereas the EWRS European Herbicide Resistance Working Group is open to any EWRS member.
There were no other matters arising that are not covered on the current agenda.
3.Likely loss of trifluralin and isoproturon
In March 2007 the EU voted for non-inclusion of trifluralin onto Annex I of the Directive and the ACP advised ministers that isoproturon based herbicides should be phased out by June 2009 due to environmental concerns. (Cholorotoluron is not directly affected by the isoproturon decision). In practice this means that both herbicides can only be used for two more seasons (2007/08 and 2008/09). Anne Thompson said that Dow will put in a new submission to try to keep trifluralin available and this is the first time a company has tried to get a new submission through before a herbicide has been finally withdrawn.
Stephen Moss asked how much impact resistance issues had on EU decisions on herbicide availability and Chris Rundle replied that it was increasingly recognised that resistance was a relevant issue in the decision making process. He added that he felt that WRAG’s past input in highlighting the importance of trifluralin in anti-resistance strategies had been useful, but questioned whether WRAG could contribute anything new to the debate to maintain the registration of trifluralin.
It was generally agreed that the loss of both herbicides will have a negative impact on anti-resistance strategies, but that trifluralin was potentially a bigger loss from a resistance management standpoint. Clare Bend stressed that trifluralin was an important herbicide in non-cereal crops, such as oilseed rape and many minor crops, and its loss would have a big impact on growers. James Clarke suggested that the document previously produced by WRAG in support of trifluralin (in October 2005) be updated and sent to Martin Ward, the new Director of Policy at PSD. The committee fully supported this approach.
ACTION: James Clarke to update the previous document. Subsequent to the meeting this was updated, circulated to all committee members and sent to Martin Ward (PSD) on 15 May 2007. A copy of this document is attached to these minutes.
4.Resistance to pendimethalin – is it increasing?
Stephen Moss showed results of a compilation exercise involving the five organisations (ADAS, AICC, GrowScience, OPS, UAP) that undertook resistance testing to pendimethalin using the Rothamsted Rapid Resistance test Petri-dish assay between 2000 and 2005. The % of populations that were rated resistant (RR or RRR) were: 2000 – 32%, 2001 – 24%, 2002 – 39%, 2003 – 64%, 2004 – 41%, 2005 – 79%. Thus there was variation between years but a trend for an increasing proportion of samples to be rated as resistant. Pooling years for 2000-2002 gives 32% of 367 samples showing resistance and for 2003 – 2005, 58% of 421 samples showing resistance. It was stressed that these samples were not randomly collected, but sent in for routine testing with a range of herbicides. However, they were not generally sent in because resistance to pendimethalin was suspected specifically, and thus could be considered semi-random.
Iain Ford showed BASF results for samples collected throughout Europe from trial sites in 2004/05 which showed a lower incidence of resistance to pendimethalin(30% of samples) in pot tests. He suggested that these could be considered random samples. His data was intended to put any increase in resistance to pendimethalin into perspective, as BASF data showed a more rapid increase in ACCase target site resistance over a similar period.
James Clarke said that enhanced metabolism tends to increase quite slowly and different active ingredients are affected to different degrees. Pendimethalin is used in the RRRT as an indicator of EM resistance and it would be expected that the efficacy of many other herbicideswould be also be affected, at least to some degree. Stephen Moss stated that in his view a critical aspect was to what degree resistance to pendimethalin impacted on its performance in the field. It is difficult to directly relate results from a Petri-dish assay to field efficacy, especially with a herbicide that is virtually always used in mixture with other herbicides. There is a lack of information on the efficacy of the pendimethalin component of mixtures. This is being addressed, to a certain degree, within the current Sustainable Arable LINK herbicide resistance and associated research projects.
5.‘Atlantis’ resistance update.
The compilation of results of resistance tests conducted on black-grass samples collected in 2006 by Bayer, Syngenta and Rothamsted were added to the 2005 information and an updated map and press article produced. This was published in Farmers Weekly 12 January 2007 showing that resistance had been found on 81 farms in 19 counties of England. The overall level of control in sampled fields was usually very good, but the presence of resistance in surviving plants is of longer term concern.
There was some debate about what proportion of ‘Atlantis’ resistance was due to ALS target site resistance as compared with enhanced metabolism. This is unclear at present – Gordon Anderson Taylor estimated that about 20% was due to ALS TSR whereas Stephen Moss thought it was probably higher, perhaps 70%. He added that Ron Marshall at Rothamsted is currently looking for ALS target site mutation in additional samples from 2006. However, ALS TSR is more likely to be picked up in the field as it confers a higher degree of resistance but, longer term, enhanced metabolism or other mechanism might be more significant. Jason Tatnell stated that, in his view, the occurrence of ALS TSR alone was likely to be rare, and that enhanced metabolism was likely to also be present in most cases.
Stephen Moss showed the herbicide histories for 10 fields where ‘Atlantis’ resistance in black-grass had been found. These showed that, on average, ALS inhibitors comprised 17% of all active ingredients used during the past 12 years, ACCase inhibitors 19%, substituted ureas 18% and dinitroanilines 25%. Consequently use of ALS inhibitors had not been atypically high. It was suggested that obtaining herbicide histories for a matching set of fields where resistance had not been detected would be useful. A debate followed into the ability to predict where resistance was likely to occur. There was general agreement that this is going to be difficult at an individual field scale, due to the complexity of past herbicide use strategies and the current widespread use of ‘Atlantis’. James Clarke asked if there was any evidence that where pre-emergence herbicides had given very high levels of control, farmers were more likely to avoid use of ‘Atlantis’ post-emergence due to resistance risks. Clare Bend answered that in her experience this was the case on a limited number of farms.
James Clarke said that WRAG should consider suggesting a ‘next-best’ strategy for grass-weed control in the light of likely loss of trifluralin and isoproturon, and probable increase in resistance to ALS-inhibiting herbicides. He suggested revising the WRAG Guidelines, last produced in 2003. It was suggested that these could include information on the best seed sampling strategy for resistance testing and include a resistance risk audit.
ACTION: All members to think about what should be included in any revised Guidelines before the next WRAG Steering Group meeting. (Note: subsequent to the meeting James Clarke and Stephen Moss attended a meeting with HGCA to discuss, with others, the production of anarable weed management guide. It was suggested that the new WRAG Guidelines might be incorporated into this document, but this requires further discussion.)
6.WRAG Steering Group membership – are any changes needed?
At the last meeting the Chairman, James Clarke, proposed that Iain Ford (BASF) and Anne Thompson (Dow) be co-opted onto the WRAG Steering Committee for the duration of the current LINK herbicide resistance project (until 2009). This was supported by all members of the Steering Committee and comments were requested from members. One response was received from Jim Orson (TAG):
“I am not convinced that the LINK project team and WRAG should be merged. Whilst WRAG could be the conduit for KT from the LINK project, I think a smaller team independent of the project team may be able to identify more dispassionately the key messages, rather than the project team that may be anxious to please its funders by 'overcooking' the results. This is not an objection but a view that needs to be expressed in the decision making process.”
The steering committee recognised the sentiment behind these comments, but did not consider that we were merging the LINK project team and WRAG. There are still people represented on just one or other of these bodies and not both. Consequently, the WRAG Steering Committee supported the co-option of Iain Ford (BASF) and Anne Thompson (Dow).
7.WRAG’s participation at the International Plant Protection Congress in Glasgow, October 2007.
Stephen Moss read out an E mail from Phil Russell with regards to a possible Resistance Forum discussion at Glasgow. Only one member was planning to attend the Glasgow Symposium and other members were reluctant to get involved without further clarification of the aims and objectives.
ACTION: Stephen Moss to contact Phil Russell and Ian Denholm to find out the current situation regarding the Resistance Forum.
8.Inclusion of resistance codes/numbers in the UK Pesticide Guide (‘Green Book’).
Dick Whitehead was considering including mode of action codes in the next edition and had asked for WRAG’s, and the other RAGs, views on this. There was unanimous support from the WRAG Steering Committee.
ACTION: Stephen Moss to feed this comment back to Dick Whitehead.
Date of next Steering Group Meetings:
Wednesday (pm) 12 December in Cambridge area (not 5 December at BASF, Cheadle as previously proposed).
The Chairman and the rest of the committee thanked Gordon Anderson-Taylor and Bayer for arranging and providing facilities for this WRAG Steering Group Meeting
Stephen Moss
WRAG Secretary 8 June 2007
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