BGTF Podcast: Dealing with black-grass resistance

Read the transcript of the podcast below.

Dr. Black Grass: Hello, and welcome to the second episode of Dr. Blackgrass on air. In this show, we'll hear from one farm and one Bayer trials site that have dealt with some really tricky resistant black-grass. This follows on from last week where we heard form Paul Neve and Gordon Anderson-Taylor about the science behind resistance. Earlier this month, I visited Bayer's Crop Open Day at Long Sutton, in South Lincolnshire, a part of the country with some quite difficult black-grass. I spoke to one farmer about what he's doing on his farm. He's based near the Boston area, and he prefers to remain anonymous, but he is happy to tell us about the situation that he's dealing with. I started by asking him how the resistance problem built up.

Farmer: We grow oilseed rape, we grow cereals. We've been encouraging black grass just from that cultural point of view for many years. Also, the herbicides that we used thirty, forty years ago, the IPUs and chlortoluron, they had a level of activity against black-grass, but it wasn't 100%. Effectively, we've been selected for resistance with herbicides on the farm. As of all our neighbors, as have most of the cultural industry, and thirty, forty years later, we've got resistant populations of black-grass, which are very difficult to deal with with herbicides.  

Dr. Black Grass: When did you notice the tipping point on your farm, that conventional techniques were not working?

Farmer: I would say it's come, in the last four or five years, it's become much more significant. We've had two or three really bad years. 2013, a lot of black-grass. I would say the last four or five years have really been a bit of a game changer in the amount of black-grass that we've seen and the resistance to the herbicides that we've used. 

Dr. Black Grass: I'm sure that story is fairly familiar to many farms. I then went on to ask him about how he's dealing with the problem.

Farmer: I suppose really focus on both cultural aspects and the ag-chem aspects of getting in amongst the black-grass, both reducing the populations in the longer term and targeting much more specifically, the fields that we know to be difficult fields for black-grass with correct timing, correct application of ag-chem.

Dr. Black Grass: Which ag-chems are you still using if you've got a big resistance?

Farmer: Liberator's a fairly significant chemical, and Avadex is very significant, plus various mixes with that. DFF, flufenacet, a load of things I can't just think of off the top of my head, but pretty much the whole spectrum. Active ingredients have been loaded on at various times in various places.

Dr. Black Grass: You're finding that these days you're applying quite significant pre-em stacks or sequences?

Farmer: We're actually decided that we can't go on applying as much stuff that's not sustainable. We're trying to use better techniques, better timings, and cultural control is much more significant. The economics of production mean that there's a limit to the ag-chem budget. Cultural control is the only way forward in long-term to reduce the general black-grass population on the farm.   

Dr. Black Grass: Okay, so what kinds of things are you doing?

Farmer: We're trying to increase stale seed-beds, trying to encourage black-grass to germinate and get it killed before withdrawing any of the crops. We have delayed drilling, which can be problematic on Hevalon Farm. We're also using more spring cropping, which again is an extension of getting stale seed-beds, getting the black-grass to germinate in a non-crop situation, and getting it killed off before we get round to Spring to drill anything.  

Dr. Black Grass: It's well accepted that stale seed-beds and delayed drilling are a crucial part of the solution, but this farmer has found that achieving a good stale seed-bed is easier said than done.

Farmer:When you go to some of the technical meetings, the people who give the presentation seem to think a stale seed-bed is a done deal, you just leave it a little while and the black-grass germinates. We find that often the black-grass has got high dormancy. On Hevalon Farm, we’ve often not got enough moisture for it to get away after harvest. We're doing two or three cultivations to try and encourage this stuff to germinate. We often find that by the time it does germinate, we're getting later in to the Autumn, and we'll often find that a stale seed-bed is actually a relatively small amount of the total seed bank in the soil. So, it can be problematic. However, if you do get a good germination of black-grass in the right situation, not too late in the year, and you get it killed off, it can be very significant to controlling black-grass in that crop in that particular year.

Dr. Black Grass:Have you experimented with different ways of promoting germination?

Farmer: Yes, we have, actually. We have very shallow cultivations, deeper cultivations, a number of passes. Also things like rolling after cultivating, which again is problematic, because if it turns right after that, you often find that the land has lost its structure and you can't get it drilled. We've done lots of things. Sometimes things that are counter-intuitive, such as rolling on Hevalon Farm late in the Autumn, in a stale seed-bed situation. We've tried lots of things. Try to adopt a sort of horses for courses approach, so that we know which fields we can target with more soil damaging techniques and which fields to avoid doing that. It's a very complex situation, there's no one solution fits all.

Dr. Black Grass: Thanks a lot. There are clearly some reasons for optimism and taking a range of approaches definitely has some benefits, but sometimes with so many different options out there, with cultivations and products, it can be difficult to know what will work well on any particular farm. To help with this, Matt Garnett and Darren Adkins of Bayer, decided to do some large-scale trials at a farm near Navenby in Lincolnshire. The farm had some highly resistant black-grass so it was an ideal place to test out the performance of a whole range of products. Matt told me more about this at Long Sutton. Matt, can you tell us a little bit about why you set up the trial?

Matt: Particularly, one of the reasons for setting up the trial is so that local farmers, local agronomists, have somewhere to look at that can compare different chemistry working in a particularly difficult situation. On this farm, we really did compare a wide range of pre-emergence applications and then over sprayed with post-emergence applications at different timings throughout the season. In particular this year, one of the best treatments that's worked is a flurtamone treatment, so it's flufenacet, DFF and a flurtamone with addition of a prosulfocarb pre-emergence, that's worked very well, and this is the third year consecutively it has worked well. To reduce numbers further, later on in the season, so we're looking in to early November timing, we've actually gone back in with Atlantis plus .3 of Liberator, that will then reduce numbers further, and that's our cleanest plot on the site.

Dr. Black Grass: Matt, you mentioned that you've been working on this site for three years. Can you tell us what the site was like three years ago?

Matt: Yes. It's on the same farm, but we use different fields, particularly because there's a serious black-grass problem. We really want to try and push the chemistry as much as possible, so we're very much similar to a commercial situation that farmers and agronomists will see out in the commercial world. We then apply a pre-emergence, so we're trying to stretch and push the pre-emergence chemistry as much as possible.

Dr. Black Grass: Okay, and what kind of black-grass populations were on this farm? 

Matt: On the farm, it's confirmed triple R resistant to Atlantis, and to fops and dims chemistry. Also, it's single R resistance to pendimethalin. Pendimethalin is still working quite well on this farm. The other chemistry, such as  prosulfocarb, and flufenacet. It's still susceptible to that type chemistry.

Dr. Black Grass: What kind of black-grass head count per square meter were we looking at?

Matt:  In the untreated this year we're looking between five hundred and six hundred heads per square meter.

Dr. Black Grass: Okay, that's quite significant. With your chemical control programs, what kind of dent we're you making in those numbers?

Matt:For example, our best treatment, which was a Vigon or Movon situation, so that's a flufenacet, DFF, and flurtamone mix. Plus the prosulfocarb, that was reducing the numbers from five hundred to six hundred heads per meters squared, down to twenty heads per meter squared just from applying that pre-em, and a well-timed pre-em.

Dr. Black Grass: Okay, and presumably, once it's down to twenty heads per square meter, you can then use a post-em product.

Matt: Yes, so now we've reduced those numbers to a much more manageable level, we can then come back in at a post-em situation and then top up the flufenacet levels, and using Atlantis to reduce the numbers even further. For example, we've gone in with Vigon or Movon, plus Defy, then followed up six weeks later with Atlantis plus .3 of Liberator. That has then reduced the heads even further to five heads per meter squared.

Dr. Black Grass: You said you'd brought about one hundred and fifty farmers and agronomists round the site, what have their thoughts been?

Matt: Their thoughts have been very positive to actually see that we can actually dosomething with chemistry and it's all to do with the quality of application and timings. For farmers and agronomists to see a range of pre-emergence chemistry and post-emergence chemistry at different timings, all in one spot, it's been very useful for people to see that all together, and have a tour around site.

Dr. Black Grass: Are you planning to do the same this autumn, going into next season?

Matt: Yes, we're planning to repeat this process and the trial next year, also coming to this autumn, so yeah, we'll keep this visual aid going.  

Dr. Black Grass: If anyone is interested in finding out more about the Navenby site, or going along for a visit, you can find out how to contact Matt or Darren on the Bayer CropScience website.   You may remember that Matt mentioned Movon and Vigon as products that performed very well against black-grass.  For those of you who aren’t aware they are pre-formulated products that are equivalent to a Liberator plus Bacara tank-mix.

Dr. Black Grass: Now for a quick roundup of harvest news.  I’m sure that everyone’s well aware of the delays in harvest because of the heavy rain over the last week, but in spite of the rain a fair amount of winter barley has already been bought in particularly in more southern areas and many people have already made a start on oilseed rape as well so far reports on yields and quality are reasonable but not exceptional but with so much still to come in we won’t have a good idea of the national picture for some time yet.  People are now waiting for a drier and hopefully warmer spell so that the wheat finishes maturing and is ready for harvest.  If you have any comments and thoughts about today’s show or about what’s happening on your farm then please tweet us at DrBlackgrass.  That’s it for episode 2 in next weeks show we will be looking at using black-grass maps and that’s available on the 5th August we hope you can join us then, goodbye


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