Ecolabs, a MN based food inspection and sanitation firm, shares are up 16c to $50.88 and sees notable activity as the May $50/$45 put spread which traded 19,000 times at 75c in what looks like an opening purchase. This would create far and away the largest positions as no other strike, put or call, in any month has open interest greater than 500 contracts. This is potentially tied to stock ad could be positioning ahead of the April 26th earnings report.