BLAINE — Dramatically higher prices for gasoline and diesel fuel needed in huge quantities for the fall potato harvest will take their toll in higher production costs.

On potato farms, petroleum products go into trucks and tractors, spray chemicals, top killer and polyethylene bags. Some growers reportedly still use a diesel mixture to kill potato vines at harvest time.

“I don’t think there’s any doubt that higher motor fuel prices will increase production costs,” said Andrew Yaeger of H. Smith Packing Corp. in Blaine, one of Maine’s largest potato dealers and shippers. “We’re keeping an eye on the situation. We don’t know how levels of crude oil are going to hold.”

Yaeger and other growers and potato market analysts were reluctant to say how much higher fuel prices would slice into break-even returns expected from the 1990 fall crop.

“Production costs as of now will be increased to a point,” said Wayne Smith of the Maine Potato Price Stabilization office in Caribou. “I personally don’t believe higher costs would be that significant. It’s too early to speculate.”

On the eve of the potato harvest in Maine, Yaeger said the production cost for the 1990 crop could “notch up” another 50 cents to $1 per barrel. Economists in recent years have pegged Maine’s potato production cost at $9 to $10 for a 165-pound barrel.

“That would include everything that is higher,” said Yaeger, “not only motor fuel. You don’t replace machinery at the price you used to. Machinery has become so expensive in the last two or three years. An added 50 cents or $1 placed onto the old production cost would have to include not only higher truck and tractor fuel, but higher machinery costs.”

The nation’s potato producers who harvest through the fall obtained record prices in the last marketing year, largely because of a second summer of drought in 1989 in the Red River Valley of Minnesota and North Dakota.