Join Date: Jun 2017
Location: middle of nowhere
Yep. You need to get them out of the pasture. That's a multi-pronged approach. First, dig them out, bag them up and burn them. This needs to be done every few months for a year or two as new ones will keep sprouting. The bigger issue is pasture management. A healthy pasture will not be overtaken by burs and weeds. Dig out what you don't want. Mow the pasture/weeds every few weeks or as-needed. Fertilize the pasture properly and don't allow it to be overgrazed.
We have a few spots in the shady part of the pastures along the windbreak where burrs, random other weeds, and nettles occasionally crop up due to pasture mismanagement from the previous owners. We mow it regularly, dig out the worst offenders, and spray along the fenceline where we can't mow (we try to eliminate unnecessary spraying). A soil sampling by the county extension showed that some fertilizer was needed in these areas in order to support the grass that will naturally keep the weeds back. The problem is 90% improved. The worst of the areas we fenced off with electrical tape until they are under control, but there is really only one or two problem spots, and they are small. If you allow the horses to get into the burrs, they spread the seeds and then you get more burrs.
Considering your situation, digging out the weeds before the burrs mature is your best bet since the facility owner isn't properly caring for the turnout areas.