Hawaii’s corn-dominated seed industry plunged 19 percent in value during the 2017-18 season, according to a preliminary government estimate.

However, shipments of seeds out of the state are projected to be up 67 percent to a record 12.7 million pounds in the season that ends this month, according to a U.S. Department of Agriculture report issued Friday. That’s up from 7.6 million pounds in the prior season. The previous high was 12 million pounds in the 2009-10 season.

Seed producers have had a presence in Hawaii since the 1960s, favoring the climate in part because corn can be planted and raised to maturity three or four times in a year compared with only once on the mainland.

Many local agriculture leaders view the seed business as a good force that has kept workers employed and farmland productive in the wake of sugar cane’s disappearance, though environmentalists and natural-­ food proponents detest the industry because much of the work involves genetic engineering. Such concerns have led to litigation as well as state and county initiatives to restrict or ban work with genetically modified organisms.

Hawaii’s seed industry is made up of five companies: Beck’s, Dow AgroSciences, Monsanto, DowDuPont and Syngenta. Together they operated 10 farms on Oahu, Maui, Molokai and Kauai covering 3,210 acres under cultivation in the most recent season. That is down 22 percent from the previous season, when there were 11 farms covering 4,090 acres.

The USDA is projecting the statewide production value of seeds this season to be $121 million, with seed corn accounting for $115 million, or 95 percent, of the total value. Various other seed crops account for the remaining 5 percent. Other seed crops grown in Hawaii have included soybeans, wheat, sunflowers, rice, rapeseed and sorghum. The final estimate for the production value of seeds in 2016-2017 was $148 million.

The peak value for seeds statewide was $241.6 million in the 2011-2012 season, which was followed by three annual declines driven by a maturing industry and corn price declines.

Since 2006, seeds have been regarded as the biggest crop in the state by production value as compared with traditional food crops, whose values are measured by crop sale value, which typically is more than the cost of production.

Hawaii’s seed crop industry value is calculated by the cost of production because the companies that grow seeds here don’t sell them. Instead, they try to produce plants with desired traits — using genetic modification and traditional breeding techniques — and the seeds of such plants are sent to the mainland for mass reproduction and sale to farmers.

The USDA estimate, which is based on surveys of seed producers with assistance from the state Department of Agriculture, is subject to possible revision.