Mich. Comp. Laws § 286.402
Whenever the director receives a petition in a form prescribed by him, signed by 10 or more grape growers in the same or contiguous townships in this state, alleging that the use of 2,4-D (2,4-Dichlorolphenoxyacetic acid), 2,4-5-T (2,4-5-Trichlorophenoxyacetic acid) or MCP (2 Methyl, 4 Chlorophenoxyacetic acid) in proximity to grape vineyards or crops of grapes described in the petition has proved harmful to the development of grapevines or the grape crop in the affected area in the same or any prior year and asking that the use of such chemical substances be prohibited or restricted within the affected area, the director shall ascertain whether at least 10 of the signers of the petition are grape growers and owners of grape vineyards within the affected area. In counting the required number of petitioners, joint tenants or tenants by the entireties shall be counted as 1 signer.
MCL 286.402