Mo. Rev. Stat. § 263.265
The county commission, township board and special road district of any county declared a Johnson grass extermination area, in addition to any and all taxing powers which it may possess shall be authorized to levy upon all property subject to its authority a tax in an amount not to exceed five cents on each one hundred dollars assessed valuation, for the purpose of paying the expenses of the county weed control board or the agent of the board in making the inspection required under the provisions of section 263.259, and for the expense of controlling and eradicating Johnson grass on county roads and rights-of-way, provided that not more than twenty-five percent of the taxes so levied and collected shall be used for administrative purposes. The cost of control and eradication of Johnson grass on all lands and highways owned or supervised by the state transportation department shall be paid by the transportation department out of funds appropriated for its use.
§ 263.265, RSMo