In a study of sugar maple sap collection through a vacuum-pumped plastic tubing system, yields were compared between tapholes in which paraformaldehyde pellets were used and tapholes without pellets, Use of the pellets did not increase yield.
Smith, H. Clay; Gibbs, Carter B. 1970. Paraformaldehyde pellet not necessary in vacuum-pumped maple sap system. Research Note NE-118. Upper Darby, PA: U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station. 4p.