Whenever any municipality shall appropriate or raise a sum of money and shall pay the same into the State Treasury for the purpose of controlling, within its borders, a forest insect or disease declared a public nuisance pursuant to section 8303, the director shall cause the amount to be expended in the municipality, together with such sum as may be determined by the director from the state appropriation made therefor. If the director finds it to be unnecessary or impracticable to expend the entire amount or any part thereof during the year following the payment to the Treasurer of State, the unexpended proportion shall be reimbursed to the municipality.   [PL 1979, c. 545, §3 (NEW).]