The latest edition of the Tillage Edge podcast features a discussion involving Teagasc’s Michael Hennessy and ADAS scientist, Dr. Sarah Cook, one of the UK’s foremost authorities on blackgrass control.
Blackgrass is now endemic in many tillage areas right across the UK. In fact, it is now the number-one weed there, according to Cook.
In Ireland, it was first identified six years ago.
Herbicide resistance is the latest challenge now confronting British farmers with many paying up to €60/ha simply to get some level of control over this highly invasive weed species.
“We spend a lot of time coming up with strategies to control it. Herbicide resistance in populations of blackgrass was first identified in 1982.
“And the problem has just become progressively worse over the years. The first resistance-related issues were identified in Essex.
“However, blackgrass is now a real challenge on arable farms throughout many parts of England, Scotland and Wales.”
According to Cook, each blackgrass plant produces 100 seeds. Each new plant will subsequently generate 10 tillers.
The weed is characterised by its ability to produce very large numbers of viable seeds on an annual basis.
Cook continued:
“We have lost a lot of herbicides over the years that would have helped manage a blackgrass infestation.
“We are down now to the last few active chemicals. But we haven’t had a new herbicide in the UK for well over 10 years.”
The loss of the herbicides, referred to by Cook, came about by a combination of resistance-related issues, as well as the removal of a range of agrochemicals by authorities.
A key feature of blackgrass is its reliance on cross pollination. Cook pointed out that such an approach to plant breeding ensures a high degree of genetic variation within a specific population of the weed.
She further explained:
“Any herbicide that does not deliver a total blackgrass kill is simply acting to favour those plants that are inherently resistant to it.
“As a result, their numbers will increase significantly with every year that passes.”
Cook also confirmed that certain blackgrass populations are resistant to a wide range of herbicides.
She commented.
“We test a range of blackgrass populations on an annual basis, of which 61% are resistant to three different herbicides.
“If chemicals are less effective, this leaves the farmer in a position where cultural control methods must take precedence.”