It's called Elephant Snot - yep, that's the brand name - and Saguaro National Park officials hope to learn by late July whether it's safe as well as effective in removing graffiti from cactuses.
"It's a viscous, goopy product with the texture of snot," and it proved "extremely effective" in removing graffiti from saguaros in tests about three weeks ago, said Brad Shattuck, chief of maintenance for the park.
"I'll be closely monitoring those saguaros until mid- or late July to see if there are any negative effects," Shattuck said. "We want to make darn sure that the cure isn't worse than the original problem."
Eleven saguaros were among 41 objects - including rocks, posts, signs and cactus - that were defaced with graffiti along the Douglas Spring Trail in the park's east district in May.
Paul Austin, chief ranger at the park, said no arrests have been made in the case.
He declined to provide further details other than to say that "the case is still open and investigation is ongoing."
Shattuck applied the commercially produced cleaning product to graffiti on two of the saguaros to test its immediate and long-term effects on the plants.
"It's a super-green product" made of biodegradable components that has been used for cleaning graffiti from brick, concrete, rocks and other materials, Shattuck said.
Made by a company called Graffiti Solutions, Elephant Snot sells for about $70 a gallon.
"I've been using it for six or seven years to clean graffiti from rocks, and it has worked wonderfully," Shattuck said. "Now we're seeing how it will work with saguaros."
While Shattuck's recent testing of the product on two saguaros proved successful at removing all but faint traces of graffiti, he said he won't use it on the other vandalized cactus until learning about longer-term effects.
"Over the next six weeks, we have a couple of concerns," he said. "Will the flesh of the cactus be hurt as a result of the application? And will the process of washing Elephant Snot off the saguaros cause the product to run into the ground and be soaked up by cactus roots?"
Shattuck said he sought to avoid root problems by using pads to soak up product runoff and prevent it from going into the soil.
"I've been closely monitoring the saguaros," he said, "and so far, it looks really good. But we'll continue to reassess to see if there is any negative effect."
Contact reporter Doug Kreutz at firstname.lastname@example.org or at 573-4192. On Twitter: @DouglasKreutz