The police, accused by the farmers of doing little to stem the flood of illegal Zimbabweans, seem to have little choice but to co-operate with the operation.
They collect the captives and take them to holding centres ready for deportation.
Among them we found Joas Mande, 61. Like the others, his hands were bound and his eyes reflected the despair of a father who would be returning to his family empty handed.
"I have two sons who want to go to University," he told me. "Now there will be no-one to support them. I have failed."
Most of the Zimbabweans said the situation in their homeland was so bad that they had no choice but to try to sneak into South Africa again.
But the farmers will be looking for them. South Africa is already home to an estimated three million illegal immigrants from Zimbabwe and they say the country has to put its own interests first.