This weed I encountered as a problem in 2020 so this year I was ready for it.
It’s a daisy, well sort of; it belongs to the Family Asteraceae and is commonly known as Bachelor’s Button.
It can be either an annual or biennial growing to 800 mm tall so it is easily visible from the road when its sticks its flower heads above the crop of wheat or barley. Also noteworthy is the fact that the blue, white or pink flowers are long lasting so the neighbours are bound to see it!
Some would consider it a “Beneficial” since it is supplied in those wonderful wild flower mixtures you can purchase at great cost or like some you can consider it a detrimental weed of crops, roadsides and other disused areas.
When you find it I would not bother with thresholds since like most pernicious weeds once established you will find it difficult to control!
Just so that you know what it is – it’s the national flower of Estonia and eradication strategies include spraying it with Glyphosate, however this has the disadvantage of kill surrounding vegetation in this case Winter wheat.