Rattail fescue is a grass weed that previously was not considered problematic, but increasing prevalence in Europe is causing concern. In the United states and Australia, major problems have been experienced with rattail fescue , where it has caused significant grain yield losses. In Denmark, the first rattail fescue was discovered in the late 1990s in red fescue fields, and a recent survey of grass weeds in grass seed crops revealed that the weed species has become common in some regions of Denmark. In recent years, rattail  fescue has also been reported more frequently in winter cereals, and often at densities of several hundred plants per square meter.

“This is a relatively new weed species, which in the beginning was very local and only appeared in some specific crops, such as red fescue. But it has become much more common and reported as a problem on many areas over time and in many crops too, in particular winter cereals and grass seed crops,” says Professor Per Kudsk from the Department of Agroecology at Aarhus University in Flakkebjerg.

He has been the supervisor of the Ph.D. Muhammad Javaid Akhter, and together with a number of other colleagues, they have published three articles and have a fourth on the way about the problem of rattail fescue in Europe with a special focus on Denmark.

“In grass seed crops, rattail is particularly problematic, not just because it causes lower yields, but also because it is very difficult to separate from the seeds of grass seed crops, especially in red fescue. This means that you may have situations where there is so much rattail fescue in a red fescue field, and that you have to give up harvesting the red fescue seeds. In winter cereal, it is more a question that rattail fescue  has potential to cause large yield losses if it is allowed to infest,” says Ph.D. Muhammad Javaid Akhter from the Department of Agroecology. 

Four publications on rattail fescue

To gather knowledge about rattail fescue, the first step for the researchers was to make a review in which they gathered all the knowledge that already existed about the weed species. In addition, they have written three more articles that go even deeper into the phenology of rattail fescue, its potential of causing yield losses in winter cereals, and last but not least, an article examining the effects of various control methods. 

“Rattail fescue has been known in Australia for many years, but here you have some completely different cultivation systems than the ones in Europe and Danmark.It is also common in the northwestern United States, but apart from this there is not much knowledge about rattail fescue,” says Muhammad Javaid Akhter. 

The publications were few, especially from Europe, which is why the researchers themselves began researching the rattail fescue to get to know it better.

"We have looked at its biology because seen from an agricultural point of view, rattail fescue has strong weedy characteristics.­­­­­ It is not very sensitive to any of the most common herbicides used to control grass weeds," says Per Kudsk .

Therefore, the researchers compared the growth and phenology of rattail fescue with three other weed species in Denmark, to find out how rattail fescue differ from them. The three weed species are:

1. Ryegrass
2. Black-grass
3. Loose silkybent grass

“We have looked at growth and phenology, that is, when does the plant reach different stages of development, when does it produce seeds etc. And in comparison, with the other three weed species, we could see that it is phenologically similar to ryegrass,” says Per Kudsk. 

Rattail fescue is a competitive weed species

In addition, the researchers have investigated the significance of the presence of rattail fescue for the grain yield. Large experiments have been conducted over two years in Flakkebjerg, where rattail fescue has been infested at various densities   in plots with winter wheat, after which the researchers have been able to look at the grain yield loss.

“We saw a clear connection between the densities  of rattail fescue and the winter wheat grain yield. And even though the experiments were made in 2017/18 and 2018/19, which were two very different years from a purely climatic point of view, the experiments show that rattail fescue is a competitive weed species that can cause up to 40% yield losses,” says Muhammad Javaid Akhter.

Rattail fescue can be controlled

In the fourth article in the series of articles on rattail fescue, the researchers looked to combat this weed species. The article has been submitted but has not yet been published. The researchers point to one thing that has meant a lot in relation to the problems that have arisen with rattail fescue, reduced tillage, which has gained more and more ground in European and also Danish agriculture.

"There is no doubt that if you choose to plough, you would have far fewer problems with rattail fescue. But there are a lot of farms, were they practice reduced tillage, and therefore we have a lot of focus on how and whether you can control this weed species in plough-free systems,” says Per Kudsk.

Integrated strategies combining cultural engineering initiatives such as multiple spring crops, late sowing of winter seeds and competitive varieties with chemical control are the way forward, whether on properties with or without plowing necessary to maintain the yields of winter seeds and seed grass in the future.

"We have looked specifically at what may be the reason why glyphosate is not very effective on rattail fescue. Our studies showed that the most likely cause is a greater activity of the enzyme against which glyphosate acts. Rattail fescue is difficult to combat chemically, which is why it is so important to gain a better understanding of its biology, and that is what we have been trying to achieve. And we believe that our results are important in relation to the above mentioned integrated strategies that can be used in the future to control of rattail fescue,” says Per Kudsk.