An Arizona copper mining conglomerate has been routinely and legally destroying hundreds of giant saguaro cactus plants, even though the plants could be salvaged and sold for prices up to $18 a foot.

Asarco Inc., formerly the American Smelting and Refining Co., obtained special-use permits to acquire and destroy the saguaro and other desert plants from the state's Land Department and the Arizona Commission of Agriculture and Horticulture. A permit was needed because the saguaro is protected by the state's Native Plants Law.

The saguaro can grow to a height of 50 feet and live as long as 150 years. With their corrugated trunks and candelabra arms, they are a distinctive sight in the Tucson and Phoenix areas. More than 63,000 acres of desert near Tucson was set aside in 1933 as the Saguaro National Monument, but conservationists say the increasing urban sprawl and pollution are threatening the cactus' existence.

State legislators and outraged conservationists have demanded to know why no attempt was made to move the cacti before they were bulldozed or buried under refuse at Asarco's Mission Mine Unit, 15 miles south of Tucson.

Asarco officials say they sought the cacti destruction permit, which essentially "sells" them the saguaro plants for $1 a foot, because their mining operation runs around the clock and "it's impossible to stop to remove the saguaros." Salvage operations would be costly and even hazardous, they add.

But state Rep. Juanita Harelson, chairman of the House Environmental Affairs Committee, said saguaro prices are high enough to make it worthwhile for landscapers to come and dig them up.

Those in the landscaping business agree.

Jerry O'Neill, owner of Tucson's Desert Products Nursery, said retail saguaro prices average between $10 to $18 a foot.

He also disagreed with company arguments that the saguaros were difficult to move. "We just shipped two of them to a museum in Tulsa, Okla.," O'Neill said.