SALEM, Ore. — Oregon lawmakers will consider creating a sales tax for marijuana in place of fees applied to growers, the method approved by voters in last year’s ballot measure legalizing the drug.

The idea is contained in a lengthy bill that is up for discussion Wednesday before a joint House-Senate committee tasked with implementing Oregon’s legal marijuana program.

Proponents of a sales tax say it might be a better way to keep retail pot prices competitive with untaxed black-market prices. They say they’d like to collect roughly the same amount in taxes as they would get from the original method.

Measure 91, the initiative legalizing the drug, calls for a tax on growers of $35 per ounce for flowers, $10 per ounce for leaves and $5 per immature plant. The Oregon Liquor Control Commission, which is responsible for regulating recreational marijuana, estimates it will raise $18.4 million in the two-year budget period that begins July 1.

A potential sales tax rate has not been disclosed. Because the fee would be a percentage of the sale price, the cost to the consumer — and the state’s revenue — would fluctuate with the price of the product.

Many lawmakers have consistently expressed concern about setting a tax rate that doesn’t drive prices so high that consumers avoid retail stores and purchase marijuana from the black market instead.

Under Measure 91, possession of marijuana becomes legal beginning July 1, subject to quantity limits.