Black-grass may be the country’s Number One grassweed problem, but the winter cereals area affected by both brome and Italian ryegrass has grown to a markedly greater extent over the past sixteen years. Wild oats are only slightly less problematic than they were at the turn of the century. And couch remains an issue across a surprisingly wide area.
These are the findings of a state-of-the-nation study of grassweed problems undertaken by Monsanto. Almost 400 growers from 50 counties of Great Britain, together responsible for over 150,000 ha of arable cropping, took part in the study, paralleling similar work in 2000.
No one will be surprised to learn that black-grass problems have grown substantially in this time, to affect just under half the winter cereals area compared with around a third in 2000.
Brome and Italian ryegrass continue to affect relatively smaller proportions of the national winter cereals area – an average 19% and 14%, respectively. However, both these problems have grown more substantially than black-grass over the years – the areas affected increasing by 72% and 55% respectively against 35% for the biggest national weed threat (Figure).
While wild oats are less widespread than they were in 2000, they still present a particular threat for many growers. At the same time, couch problems certainly haven’t disappeared.
The fact that nearly three quarters of growers report increasing problems with black-grass, almost 40% with bromes, just under 20% with Italian ryegrass and wild oats and 4% with couch in recent years underlines the threat posed by grassweeds. Worryingly, nearly a quarter of growers are seeing an increase in both black-grass and brome, just over 10% an increase in both black-grass and Italian ryegrass and around 5% an increase in problems with all three weeds.
Black-grass continues to be noticeably more problematic in eastern and central England than in the west, north and south of the country. Even so, it is now a problem on an average of between 23% and 41% of the winter cereals area in these less affected regions, with well over half of the growers in each reporting increased problems in recent years.
In contrast, brome is clearly most problematic in southern England and least so in the east, where ryegrass is also less concerning. The scale of both wild oat and couch problems is remarkably consistent across the country.
As expected, black-grass and brome problems are markedly more widespread where winter cereals are established with reduced tillage than plough-based systems. Interestingly, though, this does not appear to be the case with Italian ryegrass.