I know there is not much to see and I guess that is the point.
With beet all the “damage” is done early on.
You can be too late with the nitrogen, too late spotting pest attack and too late to kill those weeds if you don’t get down on you hands and knees early on.
There are 19 pests which attack beet including beetles, mites, caterpillars and those ubiquitous flea beetle we all just hate.
As for weeds. These are most likely charlock rather than oil seed rape and the others, pansy and fumitory