A greater number of farmers are seeing volunteer beans in following cereal crops, which if left untreated can shield other weeds from future herbicide applications.
Advising farmers in Norfolk, Andrew Melton of Frontier Agriculture has seen more volunteer beans this year than in the past.
He blames it on a combination of the widespread adoption of min-tillage encouraging their emergence with the greater area of beans being grown as the result of the three-crop rule.
“They can be seen in large clumps in the field, emerging very quickly following a few days of warm weather. They are very competitive early on in the wheat’s life, as you can imagine, and they must be removed early.”
Therefore, if you have volunteer beans in your winter wheat, they are the key driver when it comes to selecting the right herbicide to use, says Mr Melton.
It is a similar situation in the South West with his colleague Russell Dean, who looks after farmers in Dorset, Somerset and Wiltshire.
“Beans can have pods low to the ground that the harvester can miss and so dense patches of beans arise in the following cereal crop. Then you need to get rid of volunteer beans, especially if wheat is drilled early,” says Mr Dean.
“These volunteers can be competitive themselves, but because of their growth habit, they can shield grassweeds treatments, which is a serious problem,” he says.
Loss of approval
While volunteer beans are not a new problem, this year growers cannot use the mecoprop-p and diflufenican-containing herbicide Pixie, as the approval for autumn use of mecoprop-p no longer stands, explains Mr Melton.
Therefore, he used Cyclops (bromoxynil + diflufenican) against volunteer beans in wheat for the first time last autumn and says it did a good job, although he needs to learn more learn how best to use it.
“Lessons learned from last year were that it should be applied early and it doesn’t kill weeds in the same way as Pixie. You don’t see the familiar hormone twisting of the volunteers, but just an initial colour change or blotching of the weed.
“It is a learning curve as it is a different herbicide with different mode of action, but I intend to use more and to use it earlier than I did last year,” he says.
In addition, the diflufenican means that it also controls a number of difficult weeds such as pansy and speedwells.
“As a non-ALS inhibitor, it opens the door to a broader choice of following herbicides,” he says.