The worst may be over for the nation's potato chip makers, but low-quality spuds still threaten to take the big crunch out of their products.

Heavy rains and bad weather from Florida to Virginia reduced the spring potato yield by 11 percent from last year and 24 percent from 1985's bumper crop, according to the Department of Agriculture.

As a result, potato prices doubled and chip makers have been forced to use smaller potatoes, yielding smaller chips.

"The chip people got caught short, as they quite often do," said William Patterson, USDA economist. "Chipping potatoes are scarce now and the supply situation is not going to be fully relieved until the fall crop."

About 15 percent of the nation's annual potato yield is used for making chips.

Robert Marracino -- president of Detroit-based Cross and Peters Co., which makes potato chips and other snack foods under the brand name Better Made -- says this is the worst year his company has seen in its 55-year history.

"What we're getting is smaller potatoes. And for us, quality means size as well as potato quality," Marracino said.

At the height of the shortage in May and June, potato chip leader Frito Lay Inc. of Dallas had to ship potatoes from California and other West Coast areas to its chip-making plants in the Northeast, said company spokesman Charles Suscavage.

"The shortage lasted several weeks ... but as of now we're not having any problem whatsoever," Suscavage said.

Frito Lay, which has 51 percent of the chip market, buys from about 400 growers in the United States. Suscavage said he wasn't aware of quality problems.

Last week, potato prices were hovering around $14 per 100 pounds, down from $20 just two weeks earlier but still higher than in normal years when that amount sells for less than $10, according to the USDA.

Cabana Foods Inc. of Detroit has had to buy nearly half its potatoes on the open market because growers couldn't fill its contracts, said Robert Qualls, company vice president.

"They're smaller in size, the variety is not as good and the fiber is not there," Qualls said. "If we can pull through this soon we would be able to adjust."

Most Michigan chip makers haven't raised prices or changed their products' weight to stay competitive with bigger producers. "We're sitting here biting the bullet," Marracino said.

Potato chip makers use large, round white potatoes, which have to be specially grown and stored at just the right temperature -- too warm and they rot, too cool and their starches turn to sugar and turn black when cooked.

A smaller size leaves the perception that the bags, which are sold by weight, are only half full, chip producers say.

Eighty percent of chips produced in Michigan come from home-grown potatoes. Manufacturers rely on Michigan-grown storage supplies from the previous year's harvest to carry them until spring when the Florida harvest begins. But this year, storage supplies were down because of record-setting rainfall in 1986 that wiped out half of Michigan's potato crop.

Rains cut Florida's yield in half and bad weather and freezing temperatures slowed plant growth in North Carolina and Virginia, leaving local chip producers with prematurely harvested spuds that were small and expensive.