BGTF Podcast: End of season black-grass control

Read the transcript of the podcast below.

Podcast 8

Dr. Blackgrass:

Welcome to Dr. Blackgrass On Air for May, 2016. Over the next six months, we'll bring you a monthly podcast to talk about some of the main issues for black-grass control and grass-weed control at that stage of the cropping season. At the moment, one of the main things is that black-grass has now appeared above the wheat canopy. You may have seen it from your tractor cab, going crop walking, driving along an A road, or even just looking at Twitter. Clearly, when black-grass appears like this, particularly in high populations, it requires a response. In the first part of today's program, I'm going to speak to Gordon Anderson-Taylor of Bayer, about the steps growers can take to deal with the problem in the coming weeks and months. In the second part of the show, we're going to hear from one of Bayer's leading resistance specialists, Dr Roland Beffa, who is based at their laboratories in Frankfurt, Germany. He is going to tell us about resistance testing, and about how some of the work he is doing offers hope for controlling resistant populations in the future. First of all, let's hear from Gordon. I caught up with him at Bayer's Chishill Weed Screen earlier this month. Some farmers will be starting to see black-grass heads appearing above their crop, about this time of year. What can you say to them? What kind of things should they be doing immediately, and in the long term?

Gordon:

May really is a time when you can see the black-grass appear in with the crop. The first thing is just think exactly what you did that season, and is there anything that you would have changed? Clearly, you can see the results of all your efforts last time. The next thing to think about, of course, is looking forward, do we need to prevent seed shed? If you've not already sprayed out some very heavily infested areas of black-grass, it could be the last opportunity now, to treat those black-grass plants with Roundup or glyphosate, and eliminate the seed shed for the next season. It seems a bit of a shame, after you've gone through the entire season, but it will help you for the next cropping year. Of course, not quite in May, but identify the patches that you're going to take black-grass seed samples from. Those would normally be taken more in July, before the seeds are shed, but when the seed is mature. The advantage of taking a black-grass seed sample is that you can actually identify the form of resistance in that patch, and potentially, across the entire field. The reason for that, of course, is it then indicates perhaps, a most appropriate chemistry that you should be using for your black-grass control next season. The only caution I would say is if you take seed for a seed test, that certainly could take six to eight weeks at least, to be able to get a result, which often is past the time of application of pre-emergence herbicides, but it's still well worth doing, because black-grass control is a long term effort, and to know the resistance status of your population, where the black-grass is, is key to actually developing a reasonable strategy.

Dr. Blackgrass:

If people are seeing more heads above the crop than they would like, what changes can they make for next year? Should there be any radical changes in rotation or chemistry, or that kind of thing?

Gordon:

Again, just looking backwards, first of all, at the chemistry you used in the previous season, and think, "Was I perhaps a little bit over-cautious with my applications? Should I be stacking my pre-ems a little bit higher, to get improved control of the pre-emergence timing? Or was my false emergence product put on too late, possibly in the spring, rather than in the autumn?" You can look at the chemical program first, but after that, if your chemical program was reasonable, it was applied in good conditions the previous season, it's still not being effective, then clearly you've got to look at the cultural aspects. Integration of the chemical and cultural is the absolute requirement, in order to obtain control in many situations. Essentially, what you need to look at first of all, are probably the easier options of looking at things like delaying your drilling date by two to three weeks. That will have a dramatic impact on the amount of black-grass that comes up in the crop. Possibly drilling in a more competitive crop, looking at your seed rates, all these are relatively easy options. If you can't tackle it that way, then you may be looking at more dramatic change – actually changing your cropping pattern, and the ultimate change is moving into a spring crop, which again, if you can control black-grass in the spring crop, you've then got opportunities for stale seedbeds, obviously. You've got periods during the winter, where you may be able to control black-grass that emerges. Then drilling in the spring, when black-grass germinates less - you're less likely to actually suffer from significant populations in the following season.

Dr. Blackgrass:

Gordon, to finish off, what would you say to farmers who have seen a lot of black-grass on their farm this May, and they're really beginning to question how they're going to control black-grass in the future? Gordon: I understand that totally. The situation can be overwhelming, but it's important not to get overwhelmed by it. First of all, know what your problem is. Identify where it is. Identify its resistance status. Then at least you know what you're trying to tackle. After that, look at the options that are open to you. Whether that be delayed drilling or spring cropping, or modifying your chemical program, or indeed, things like cover crops, moving to spring cropping. There's a lot of options out there. See what fits into your farming system, decide exactly the program to adopt, and follow it through. It's not a short term strategy. There are instances where people have overcome difficult black-grass problems. It's not an impossible situation. It's just something that needs tackling over a period of two or three years. But certainly, it is achievable to get your population down to acceptable levels, which not only obviously means your profitability will increase, your yields will increase, but also the farm will look a lot better. It's not the end of the world.

Dr. Blackgrass:

Thanks a lot, Gordon. One of the main things Gordon talked about was getting a resistance test done. If you have a difficult population of black-grass, and have never had a test, or not had one recently, it is definitely worth considering. The first step is to speak to your agronomist or local member of the Bayer technical team. You can discuss your black-grass problem with them, and they will help you identify which resistance tests you need. In addition to Bayer's tests, there are other tests commercially available. For people who do have their resistance test done by Bayer, all the samples are sent off to Frankfurt in Germany for analysis. In Germany, a team of scientists led by Roland Beffa, look at these samples and analyse what level of resistance they have. I spoke to Roland earlier this month, when I visited the facility. Roland, could you give me a quick outline of what happens to samples of seed and of plants that are sent from the UK, to the labs here in Germany?

Roland:

The seeds we receive are first analysed in the greenhouse for resistance to different herbicides, or different sequence of treatment, or mixtures, and the resistant population, we can also take plants and analyse later on in the laboratory, as we do for the plant samples, we receive directly from the field. These plants will be analysed for two types of resistance. First type is target site resistance, where we analyse by genetic analysis the mutations which occur in these plants. Also, the plants will be measured for metabolic resistance. These plants will be treated with radioactive herbicides, and then the analysis we will do, related to the capacity of the plant to metabolize or detoxify the herbicides. The target site, we analyse mainly ALS and ACCase mutations, because they are relevant for UK and for metabolic resistance. At the moment, we analyse mainly ALS inhibitors, different inhibitors, and on demand, we can also analyse ACCase inhibitors.

Dr. Blackgrass:

At the moment, we send samples to Germany to test. Will there ever be a time when we can test things in the field, or at least very local laboratories?

Roland:

This is our dream, especially for metabolic resistance. I will say for target site, we can develop today, certain methods which we can foresee testing directly in the field. Maybe in a timeframe of two to three years from now. For metabolic resistance, it's much more difficult. We need first to understand, what are the genes which are involved in detoxification of the compounds? There is a lot of research to do, still, and probably we cannot do that at the field level for the next five years. Nevertheless, our goal is, try to decrease the time for response for our analysis in the laboratory. At the moment, it's a timeframe of two to three weeks. By improving our methods, we try each year, to come to less and less time for answer.

Dr. Blackgrass:

Could I ask you just a little bit more about the metabolic resistance? You're testing that it can metabolize ALS inhibitors, but does this mean it can also metabolize other chemical groups, other actives, more effectively, as well? Really, is there cross resistance?

Roland:

Yes. Metabolic resistance is not related to the mode of action. It's related to the chemical structure. This means that the population which has metabolic resistance to ALS inhibitor, can also show metabolic resistance to ACCase inhibitors or other chemical classes which have some other mode of actions. We have the example already, of populations from the fields which have broad metabolic resistance, and which are resistant to even new chemistries.

Dr. Blackgrass:

It's possible that even if a new mode of action is discovered, there will already be a very well-developed capacity for resistance in existing populations.

Roland:

This might be possible for existing resistant populations. Fortunately, it will not be, from my point of view, a high number of populations. But you will be able to find it. Dr. Blackgrass: OK, so UK farmers send their samples in. They get their results back and identify certain levels of resistance in the target site and the EMR. What should they do with this information?

Roland:

Our colleagues who are in contact with the farmers will use this data to refine the recommendations for further treatments. For example, we know that not each target site has the same weight of resistance. We know that we can find metabolic resistance to one given compound of a chemical class, but not the other, for example. This helps us to define which herbicides are best to overcome this resistance.

Dr. Blackgrass:

Finally, can you use the learnings you have about mechanisms of resistance, to identify new actives to use, and new compounds?

Roland:

Yes. This is also one of the outcomes of our studies. We try to really characterize very well reference resistant populations, and these reference resistant populations are introduced in our screening.

Dr. Blackgrass:

So screening is when you're testing compounds at the beginning, to see if they have any beneficial effects for weed control?

Roland:

Yes. And of course, the compounds which are not cross-resistant to these reference resistant lines are a very good candidate to develop new herbicides.

Dr. Blackgrass:

Thanks a lot, Roland. There’s some real points for optimism there. Particularly that there might be a fast test for target site resistance and even metabolic resistance in the not-too-distant future. But as we're dealing with fast-evolving weeds, there were also points for concern, particularly that the metabolic resistance can be to multiple compounds, not just one. That's all for Dr. Black-grass On Air in May. We'll be back in June with a roundup of what we found out at Cereals. I hope you can listen to us then. Goodbye.

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