It was years in coming, but in November, a major buyer of American leaf finally told tobacco growers it will not purchase any tobacco that contains residues of the growth regulator maleic hydrazide (MH).

“In response to customer feedback and new customer requirements, Universal Leaf of North America has made the decision to not allow the use of maleic hydrazide on any tobacco contracted in 2011,” said George Scott, vice-president for leaf of the leaf dealer, in a Nov. 16 letter to the company’s contracting farmers. “We will be performing residue testing on tobacco grown in 2011, and if your tobacco is found to have any MH residue, your contract will be terminated.”

MH controls the growth of suckers in the leaf axils, so that the suckers don’t drain the plant’s resources from leaf growth. Combined with timely removal of the flowers at the top of the plants (called the tops), MH has allowed growers to consistently increase yields.

It’s not like all this was a sudden development: One set or another of tobacco buyers have been threatening to prohibit MH since W.K. “Bill” Collins first took a tobacco agronomist job with the state of North Carolina.

That was in 1956.

“This is a controversy that has been going on almost constantly for 50 years,” said Collins, who is now on the staff of North Carolina State University. “Many buyers around the world have looked at MH and said they didn’t want it in their products. Now one has taken the step.”

“No buyer or anyone else has ever been able to demonstrate any physiological reason to prevent its use. There is no — repeat no — negative health impact for humans from MH,” said Collins. But that hasn’t mattered to buyers, especially foreign ones, who wish to avoid the presence of any systemic chemical in their finished products.

As this story was written, only Universal Leaf had pushed the MH panic button, but if MH-free leaf turns out to be a competitive advantage for anyone, Collins thinks the others will soon have to follow suit.

“The bigger question now is whether companies that make this change will provide adequate compensation to the farmers,” he said.