The History of Paraformaldehyde Use in the Maple Syrup Industry

Like with seeded agricultural crops, maple syrup production, also a plant-based crop, faces the challenges mother nature and the natural environment throw at it.  The challenge has been finding safe and effective methods of overcoming the battle with microorganisms, like bacteria and fungi, that also want to enjoy the sap of a freshly tapped maple tree. Applying pesticides has been a solution in agriculture and food production for eons, and, for better or worse, the maple industry was not spared. Unbeknownst to many, since pesticide use is not allowed today, the previous century was witness to the maple industry working through its own history of finding, embracing, and ultimately abandoning, pesticides in the sugarbush.

In the early 1950s, research began for the development of an antimicrobial application that could be used to slow or eliminate the detrimental effects of microbial growth on sap quality and sap flow at the tap hole of the tree. Researchers at the USDA Northeast Lab, the University of Vermont, Michigan State, and MacDonald College in Ontario all confirmed that the slowing of sap flow, and in some cases stoppage, over the course of the tapping season was in part attributed to the growth of micro-organisms such as yeast and mold at the area of the taphole.  The tap hole was in effect a fresh wound in a tree that emitted sugar rich sap, a welcome environment for microbial growth.

Putnam Robbins demonstrating the insertion of a paraformaldehyde tablet into a tap hole.

Looking for a way to counteract this microbial growth, in 1956 under the direction and funding of C. O. Willits at the USDA’s eastern regional research laboratory, researchers responded with various approaches to tap hole sterilization and improved sanitation. The bulk of the research and development effort was carried out at Michigan State University by forestry professor and maple specialist Putnam Robbins and microbiologist Robert Costilow. Robbins and Costilow experimented with a variety of chemical treatments and methods, eventually settling on trioxymethylene, also known as paraformaldehyde.[1]

Robbins and Costilow found a small pill-like tablet with 250 milligrams of paraformaldehyde embedded in agar to be the simplest and most effect method to administer the chemical at the taphole. Sometimes called PF or PFA pellets, the pellet would be inserted in the fresh drilled tap hole prior to the insertion of the spile, and the agar would slowly dissolve over the course of the season.

Paraformaldehyde tablet going in a freshly drilled tap hole.

Research by Robbins, Costilow and others examined how much PFA residue remained in maple syrup made from PFA treated sap holes.  They found that the overwhelming percent was less than 1 parts per million (ppm) and that 100% of syrup samples tested were less than 2 ppm. Robbins and Costilow began promoting the idea of use of the pellets in 1960 and submitted an application for approval for manufacturing and use to the Food and Drug Administration (FDA). Paraformaldehyde was registered with the EPA as a pesticide with approval to distribute for use as a disinfectant for bacterial plant pathogens and fungal diseases in maple tree tap holes and went into use for the 1962 maple sugaring season. Formal approval for use began when the tolerance levels were published on February 20, 1962 in the Federal Register under 21 CFR 121.1079. At some point oversight shifted to the EPA and it was moved in 1975 to 21 CFR 123.330 for regulation by the EPA. Based on Robbins and Costilow’ s research, tolerance level for PFA in maple syrup chosen by the FDA was set at not to contain in excess of 2 ppm of PFA. The decision to set the tolerance level at 2 ppm was somewhat controversial, since later studies found naturally occurring levels of PFA being higher than 2 ppm in completely untreated trees, and treated trees showing zero ppm.[2]

1967 advertisement from R. M. Lamb company promoting their sale of the Flomor brand paraformaldehyde tablet.

With PFA being approved for use by the maple industry, three manufacturers were registered to produce the pellets, all three of which were prominent sellers of maple equipment and supplies. Lamb Natural Flow, Inc. of Liverpool, NY made Flomor brand pellets, Sugar Bush Supply Company of Mason, MI made Ma-pel brand pellets, and Reynolds Sugar Bush of Aniwa, WI in conjunction with the Vicksburg Chemical Company of Newark, NJ made Sapflo pellets. A bottle of 500 pellets generally sold for $5.00 at that time.

As hoped, application of PFA pellets to fresh tapholes resulted in substantial increases in sap production over the course of the season with a 20% increase on average and as much as 50% increase in some cases. One pellet manufacturer and large-scale producer even went so far as to say the pellet was “probably the most significant profitability tool that has ever been developed for our industry.”[3]

1967 advertisement from Vicksburg Chemical Company and their partner Reynolds Sugarbush promoting the Sapflo brand paraformaldehyde tablet along with Fermaban and Myverol, their other chemical preservatives for maple syrup and maple confections.

Manufacturers and marketers of the PFA tablets heavily promoted their use in conjunction with the shift to plastic tubing. The projected increases in sap production from the use of PFA pellets together with plastic tubing were enormous and potential game changers. As with plastic tubing, the use of a chemical aid was viewed by some as simply modernization with the aid of science and technology. Some may even say, better living through chemistry, as the Dupont advertising slogan went. In fact, as noted above, one of the three manufacturers of the PFA pellet was Bob Lamb, the maker of Lamb Naturalflow, tubing, who became the most influential manufacturer and promoter of plastic tubing in the United States during the 1960s and 1970s.

Advertisement from 1964 for the Ma-pel brand of paraformaldehyde tablets as sold by Bob Huxtable’s Sugar Bush Supplies Company out of Lansing, Michigan.

The pellets were clearly effective in slowing microbial growth and increasing and extending sap flows during the tapping season; however, several researchers and producers recommended against their use due to the adverse effects of the pellets on the short- and long-term health of the trees. In addition, the mere use of the word “formaldehyde” in association with food production was very unpopular with consumers. Combine that with a growing interest by the maple syrup industry in organic production, labelling, and marketing put the use of PFA pellets further out of favor. At the same time, there was strong push-back from some corners within the industry that the pellets were harmless. Not surprisingly support for the use of PFA was especially strong from the large producers and manufacturers of the pellets, most notably from the influential Robert M. Lamb and Reynolds family, with Lynn Reynolds, serving as the President of the International Maple Syrup Institute at the time.[4]

Ultimately, the state of Vermont appears to have been the first government (state, federal, or provincial) to formally ban the use of PFA pellets, reportedly doing so around 1982. It is interesting to note that a number of references make the claim that Vermont led the way with a ban around this time, yet I have been unable to identify and document the regulatory action or Vermont statutes to support this claim and this date. Likewise, I have been unable to find any news reports from that time announcing the action of the State of Vermont. This is not to say that I don’t believe that the State put in a ban of some sort, rather, it is remarkable that it has been so difficult to verify the details and date of that regulatory action.

By the end of the 1980s, two decades of research demonstrating the ill-effects of the pellets on forest health and sugarbush productivity had convinced most producers to discontinue their use. At the federal level in the United States approval for distribution of PF for use in the maple industry was cancelled by the end of 1989, effectively banning its use. In Canada registration for the use of PF expired at the end of 1990, effectively resulting in a ban on its use beginning in 1991.

Banning of the PFA pellet in the United States was specifically carried out in two ways. First through the voluntary cancellation by the registrants of approval to distribute PFA pellets. Approval to distribute had previously been awarded by the EPA to the three companies manufacturing the pellets. In 1986 Reynolds Sugar Bush, Inc. (Sapflo) cancelled their registration, while Lamb Natural Flow, Inc. (Flomor) and Sugar Bush Supply Company (Ma-pel) both cancelled theirs in 1989. In addition, in 1999 the EPA revoked the previously established tolerance level for residues of paraformaldehyde in maple syrup with publication of the revocation as a final rule in the Federal Register.

In Canada the last registered product containing paraformaldehyde for use as an antimicrobial agent in maple syrup expired on December 31, 1990, effectively making its sale, purchase or use illegal after that date. However, a maximum residue limit of 2 ppm of paraformaldehyde in maple syrup remained on the books until a proposed revocation in 2010. From time to time, examples of its continued use have appeared in the news.For example, investigations in Quebec in 2001 discovered continued use of PFA pellets by sugarmakers with evidence of PFA pellets found at 21 of the 50 sugarbushes visited.[5]

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[1] J.M. Sheneman, R. N. Costilow, P.W. Robbins, and J.E. Douglass, “Correlation Between Microbial Populations and Sap Yields From Maple Trees,” Food Research 24 (1958): 152-159.

[2] Putnam W. Robbins, “Improving Quality and Quantity of Maple Sap,” Proceedings of the Fourth Conference on Maple Products, Eastern Research Utilization and Development Division – USDA (1959): 42-46; “New Pellet Can Increase Maple Syrup Yield 50 Pct,” Traverse City Record-Eagle 16 November 1960, 14; R.N. Costilow, P.W. Robbins, R.J. Simmons, C.O. Willits, “The efficiency and practicability of different types of paraformaldehyde pellets for controlling microbial growth in maple tree tapholes,” Michigan Agricultural Experiment Station Quarterly Bulletin 44, no. 3 (1962): 559-79; 40 CFR Part 185.4650.

[3] Lynn Reynolds, “Editorial,” Maple Syrup Digest 1A, no. 1 (1989): 16-17.

[4] A.L. Shigo and F.M. Laing “Some Effects of Paraformaldehyde on Wood Surrounding Tapholes in Sugar Maple Trees,” U.S. Forest Service Research Paper NE-161. (1970); R.S. Walters and A. Shigo, “Paraformaldehyde Treated Tapholes, Effects on Wood,” Maple Syrup Digest (1979) 19 no. 2 (1979): 12–18; M.F. Morselli, “Effects of the Use of Paraformaldehyde Pellets on Sugar Maple Health: A Review,” Maple Syrup Digest 7A, no. 3(1995): 27–30.

[5] “40 CFR parts 180, 185, and 186 – Tolerance Revocations for Certain Pesticides,” Federal Register, Wednesday, April 7, 1999, vol. 64, no. 66, p. 16874-16880; Established Maximum Residue Limit: Paraformaldehyde EMRL2011-05. Health Canada Pest Management Regulatory Agency, March 14, 2011; “Maple-syrup producers sour: Quebec farmers seek federation’s action to curtail use of banned chemical on trees,” The Gazette 18 July 2001.