Everything you need to know about regaining control
In addition to rotational ploughing, stale seedbeds, delayed drilling and spring cropping, a large number of cultural practices are now being widely used to control grassweeds, according to the 2016 National Grassweed Study.
The average winter wheat herbicide spend recorded in the latest Monsanto study of almost 400 farms with over 150,000 ha of arable cropping is currently £89/ha, with a third spending over £100/ha and more than one in every 10 over £125/ha (Figure 1).
For the most effective long-term black-grass control, growers and their advisers need to apply the most effective control tools in five main areas - cultivations, sowing date, crop competition, herbicides and seeding prevention, recommends Dr Stephen Moss. “And they need to keep up their efforts for at least five years.
The increasing difficulties being caused by grassweeds are clearly reflected in the changes recorded in both chemical and cultural control practices by extensive grower studies conducted by Monsanto over the years.
Herbicide resistance is clearly the most important factor behind the increasing grassweed problems identified in a state-of-the-nation study of grassweed problems undertaken with almost 400 UK growers by Monsanto.
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.
Brome and Italian ryegrass infestations have been growing notably faster than black-grass in recent years, reveals a state-of-the-nation grassweed study. Wild oats are only slightly less problematic than they used to be. And couch remains an issue across a surprising area.
Seeds of both Wild Oat species tend to have longer dormancy, and be slightly more persistent in the soil, than Black-grass, Italian Rye-grass and Bromes
Wild Oats were the major weeds of arable crops in the late 1970’s largely due to a move to more intensive arable cropping and the lack of effective herbicides.
Why does identification of species matter?
In the UK, there are two main species which frequently occur as weeds of arable crops.
Italian Rye-grass is an annual grass-weed propagated solely by seeds and, if uncontrolled, weed populations can increase rapidly.
Problems in controlling Italian Rye-grass tend to be more restricted to specific areas compared with the more widespread problems with Black-grass
Italian Rye-grass is about twice as competitive as black-grass on an individual plant basis and five rye-grass plants/m2 typically causes a yield loss of 5% in cereals
Italian Rye-grass can be distinguished from perennial rye-grass by two characteristics
Couch grasses owe their success to their ability to spread by means of horizontal stems growing through the soil (rhizomes) or across the surface (stolons).
In a survey published in 1910, Couch was reported to be the most problematic weed of arable crops in the UK, just ahead of charlock
Dense infestations of Couch may produce several hundred heads/m2 reducing cereal yields by 25% or more
Herbicide resistance has not been detected so far in any UK Brome species although two populations of Sterile Brome showing higher levels of tolerance to glyphosate have been found in Leicestershire and Oxfordshire.
Black-grass is a medium to large annual grass-weed which is increasingly common on arable land. It is propagated solely by seeds and, if uncontrolled, weed populations can increase by >10 fold/year.
Black-grass occurs throughout much of Western Europe and is an increasing problem in eastern and northern Europe too.
Black-grass can seriously reduce arable crop yields through competition for nutrients, especially nitrogen. Effects on crop yield vary greatly due to the relative competitiveness of crop and weed - a competitive crop can effectively suppress black-grass.
Well planned management methods to regain control of Black-grass; integrating chemical and cultural controls.
Common couch is characterised by having creeping, white underground stems (rhizomes), shoots with small auricles and a short ligule at the base of the leaf blade.
In the UK, there are five main species of brome which frequently occur as weeds of arable crops
In the UK, there are five main species of perennial grass weeds of arable crops that are commonly known as couch or twitch
Two species of rye-grass commonly occur in the UK: Italian rye-grass (Lolium multiflorum) and perennial rye-grass (Lolium perenne).
Why does identification of species matter?
Bromes are some of the most competitive grass-weed species with similar competitive abilities to wild-oats and Italian rye-grass
Brome species emerged as a problem in the late 1970s and early 1980s with a shift towards more autumn cropping and non-inversion tillage.
Bromes are annual grass-weed propagated solely by seeds and, if uncontrolled, weed populations can increase rapidly
Wild-oats are one of the most competitive of the common grass-weed species with similar competitive abilities to Italian rye-grass and sterile brome
