John Marshall, CSD E & D agronomist - Dalby, examines the impact of Roundup Ready® Cotton since its introduction to the cotton industry in 2000.

What has the uptake of Roundup cotton been like since its introduction?

The Roundup Ready® technology was introduced through CSD varieties in the 2000-2001 season – 6 years ago and during the intervening period, there has been a dramatic increase in the uptake of the technology, there being a few different reasons for this. Quite obviously, a lot more varieties have become available, particularly in the Bollgard stack group, and some very high performing ones amongst them.

Growers have good varietal choice in the technology. As well, there has been a pretty dramatic change in attitude by growers to things like chipping, other practices have come in and things like the availability of new herbicides for control of volunteers have all made a big difference in the use of the technology.

There has been a number of management changes that have occurred with the use of Roundup Ready cotton. Can you go through some of the key ones?

When you think back six years ago and consider practices which most growers were using then, you realize how many changes there have been. Things like planting cotton into shoulder cereal stubble, which offers a lot of advantages from a resource sustainability point of view. The expanded use of narrow row cotton – 15 inch cotton. The Roundup Ready technology, in conjunction with modifications of picking fronts has made that much more feasible. Another is the reduction in use of residual herbicides.

There is obviously a lot of advantages in that change, in situations when early season runoff occurs, and in obtaining a better plant establishment. This reduction is spread across pre-plant herbicides and in bands at planting. Correspondingly there has been a reduction in early cultivation and we know early cultivation has certainly been tied in with the increase in diseases like Fusarium. So that’s just touching on a number of the key management changes that have occurred with the uptake of the Roundup Ready technology.

Roundup Ready is obviously an excellent tool for growers to use. Where does the technology fit in as a part of an integrated weed management package?

It is another valuable tool that has come along and I guess the important thing is for growers not to over use it but realize that it is just one component of a package. So practices like a light chipping has still got a role because there is still nothing better than chipping for picking up escapes and that’s what resistance management with weeds is all about. It’s to pick up those ones that get away.

On the same vein, there is still a need there for opportunity cultivation in some instances, and the other thing is growers need to be looking at the herbicide groups they are using and make definitive decisions about rotating between those groups. It might seem a very narrow point of view but the thing about herbicide resistance more so than with insecticide resistance is that the individual with the problem will feel most of the impact for some time. It is important to use all the tools available in the package to prevent the situation developing.

Just focussing now on this season’s Roundup Ready crops, many of these are now approaching a critical time. Can you give us a few comments on that?

Out there this year, there is a lot of Roundup Ready cotton, whether it be in the stack varieties or as straight Roundup Ready, possibly in excess of 70% of the industry. There are a lot of fields that are moving into the stage where growers are looking at the first over the top application. It’s an important part of the technology and its very crucial that growers, when they are putting that application on, think about the product their using and the conditions they are applying it under. Cotton growers have used glyphosate for pre-plant control for years and there has never been a lot of concern about drift or damage to neighbouring fields or neighbouring crops on other properties. But with the Roundup Ready herbicide and over the top application, a lot of things have changed.

There is a much greater spread of planting times through most valleys now. It is a very concentrated product growers are using for the over the top application and it’s being applied, particularly on bare fallow fields where there is not much stubble and its very smooth, onto something that is not a very catching surface. It’s important that when it is being put on, the applicator is thinking about where it is going to end up - simple things like using smoke or visable indicators right through the operation are critical to help ensure the product stays on-farm.

After the closing of the over the top window, growers can use Roundup Ready herbicide through shielded sprayers for application. This is another important management practice with the Roundup Ready technology. What are some of the important issues when using Roundup Ready herbicide through shielded sprayers?

When we look at use of the Roundup Ready package, growers tend to use either one or two over the top and then conversely one or two applications in crop. There can be a tendency for growers to be a little bit indifferent to the damage that can be done during a shielded operation. The thing to remember is that the product offers only vegetative tolerance to Roundup herbicide. Once the flowers are initiated even in the formative stage there can be damage to pollen – this has consequences for both late over the top applications and untidy applications through shielded sprayers. So it is important that the product be kept off the foliage after the 4 true leaf stage and thus prevent it moving into floral parts.

Just simple basic things like using as big droplets as is possible, going steady and keeping the speed in that eight to twelve kilometres range, setting the shields up well so that will reduce the amount of leakage and basically just thinking about the job that is being done and not rushing it. Do it when conditions are ideal for the product to end up where it is aimed for and that’s not on the cotton plant but on the weeds below it.

Looking to the future, what are going to be some of the issues with Roundup Ready Flex® and what differences will that make to the current Roundup Ready technology?

If everything goes well for Monsanto with registration, the industry will start to see the new product the Roundup Ready Flex in small areas for next season. The standout advantage of the new product is the fact that it can be applied over the top of the crop for an extended period after the four true leaf stage. So it’s a safener as far as the early stage weed control goes, and it means that a much more efficient job can be done with later weed control and all the advantages that come with the Roundup Ready technology such as opportunity cropping and narrow row cropping. They all just widen out. It makes the product that much more sustainable and a key part of the whole cotton system.

Many growers have got a taste of the opportunities offered with the Roundup Ready technology - this is just going to widen with the new product.

The CSD team in collaboration with a number of Cotton CRC Researchers have put together some information similar to what you are talking about today. Can you give us a bit of a rundown on how industry people can get hold of that?

We thought it was very timely to pull together a lot of the trial work, observations and grower experiences with Roundup Ready technology that have occurred over the last six years, considering the large proportion of cotton farms that now have some Roundup Ready.

What we have tried to do within this publication is pull a lot of these findings together, and present them as reminders and suggestions to users of the technology as a way of getting the best value from the product for the whole industry.

Further Information:
Robert Eveleigh, John Marshall,  Craig McDonald, David Kelly or James Quinn