The 2020 maple sap harvest and maple syrup processing season is underway in southern areas of Ontario.  Many producers in southern areas have their sugar bushes fully tapped and are busy processing new syrup, while others are still working on completing tapping their trees.  The first sap harvest and boil occurred in the earliest southwestern areas (London-Chatham-Sarnia) the first week of February.  Mid-season southern areas had their first sap run and boil occurring the third and fourth weeks of February.  From weather forecasts, numerous sap runs will occur in the coming days across southern regions.

For sap flow conditions, watch for consecutive days of thawing daytime temperatures with freezing night time temperatures, ideally +5 ⁰C day and -5 ⁰C night.  Trees that are deeply frozen require several days to thaw before sap flows.  Low atmospheric pressure during the thaw period often produces a faster flow of sap, but not always a higher yield.

Maple syrup producers can continuously evaluate the health of their sugar bush as the harvest season progresses and throughout the year.  As most producers already know, the health of the sugar bush should always have top priority when management and sap harvest decisions are made.  In most regions soil moisture levels and snow cover have been good during the current winter and maple trees are in a healthy condition for the 2020 syrup season, where various environmental or nutritional stresses have not been a factor.

There are a few recent 2019 environmental stress events to consider,

• In northern and eastern areas of Ontario, many sugar bushes experienced moderate to severe defoliation caused by Forest Tent Caterpillar.  Severely defoliated sugar bushes may produce lower sap sugar concentration during the 2020 sap harvest.  Healthy maple trees usually recover after enduring one or two years of defoliation outbreaks during subsequent growing seasons, if they are not already under stress due to other factors.  Multiple stressors can kill the trees.
• Increased activity and defoliation caused by Gypsy moth larvae was reported in many areas during summer of 2019.  Overwintering eggs of Gypsy moth are reported to be abundant in broad areas of southern Ontario, which will hatch during May 2020.  Producers can monitor larvae activity and defoliation in late June and July this coming summer.
• In low areas and imperfectly drained sites, sugar bushes that experienced flooding or excessive soil moisture during late spring and into early summer (2019) due to frequent prolonged rain may still be recovering from root injury where drainage was not adequate.  Sugar maples are more sensitive to root injury than soft maples to excessive soil moisture if it occurs during the growing season.  Adding a drainage ditch in a few key areas can help improve soil aeration for roots by removing excess water from sensitive root zones during prolonged rain.

Tapping tips

Sustainable tapping

Growing new sapwood (annual growth rings) at an average rate or greater, and preserving existing conductive sapwood for future syrup production is the objective of managing a healthy sugar bush.  Every time a tap hole is drilled, a quantity of healthy sapwood is permanently removed from providing sap in the future, called a stain column or non-conducting sapwood.

By following the tapping guidelines and staying current on Good Sugar Bush Management skills, syrup production should be possible each year and for future generations of producers.

Long-term research on the relationships between tapping a tree, the growth response of maple trees to sap harvest and the accumulation of non-conductive sapwood at various tapping intensity has provided conservative and sustainable tapping guidelines for the industry.  Add climate change as another factor and this long-term research will become increasingly important in the near future.

When deciding where to locate a tap hole, try to select an area on the trunk where no previous taps have been drilled to avoid drilling into non-conductive wood.  Or locate an area where new sapwood has accumulated to two or more inches over previous tap holes and non-conductive wood.  This can be very difficult when the person tapping can’t see into the trunk, or where no systematic tapping pattern has been followed over the years.

Researchers have devised a method of determining whether sustainable tapping practices are occurring.  Look at the colour of the wood shavings on the tapping bit counting ten tap holes.  If 9 or more out of every 10 tap holes drilled have creamy white wood shavings and only 1 shows dark brown wood shavings, this is a good indicator that sustainable tapping practices are being followed and the trees are healthy.

Reference: Dr. Abby van den Berg, Proctor Maple Research Centre, University of Vermont

If fewer than 9 tap holes out of 10 holes show creamy white wood shavings, this indicates that tapping practices are not sustainable.  The trees may not be growing enough new sapwood each spring and summer to replace the sapwood that is being removed by tapping. There may be problems with soil nutrition, drainage or pest activity.  Excessive tapping may have occurred in the past.

Made available by the North American Maple Syrup Council, maple producers from all provinces and states can now search online for maple related information from a large bank of scientific knowledge.  Visit http://mapleresearch.org .  Anyone who is interested in learning how they can participate or contribute to the international maple research effort can contact the NAMSC.