A former district councillor has called for a rule change to allow for prosecution for effluent spillage on highways and in public places.
Dr Barrie Wills, who was a Central Otago district councillor, says the Otago Regional Council's transport plan should be amended to add a "simple" set of rules to address the issue.
But the regional council says rather than enforcement, the best mechanism for reducing effluent spillage is good practice from farmers and stock truck companies.
Trails of "green gunk" on highways and through local towns over the past several weeks were a result of stock trucks moving dairy cows south from winter grazing in Central Otago, said Wills, who is the principal consultant at Central Environmental Services.
"This concentrated effluent ends up polluting our waterways and creates a slippery, dangerous surface on our highways."