Tree Care
events occur at a certain number of growing degree days. Lilacs bloom between 80
and 110 GDD, spruce spider mites hatch
at 162 GDD, and the northern catalpas
first bloom at 675 GDD.Whether you are
in southern Illinois, or northern Michigan, you can track growing degree days to
predict the occurrence of almost any natural event. So what do we do with this
info?
Using phenology
There are several different ways to put
phenology to work for you. First, as there
are many events that occur at roughly the
same number of growing degree days, you
can use the occurrence of one, more conspicuous event, to predict the occurrence
of something less obvious. For example,
the emergence of emerald ash borer
(EAB) adults goes unnoticed by pretty
much everyone. They are small, they fly,
and they leave the tree they exited from shortly after they come out.
So how can we easily know when new EAB infestations may be
possible? If we look at their GDD info for their emergence dates,
we find they come out at about 550 GDD. Checking a list of other
EAB emerges when black locust flowers.
GDD events, we see the black locust
(Robinia pseudoacacia) begin to flower at
548 GDD, so we can surmise that if we
see black locust trees in bloom, EAB
adults are out and looking for new ash
trees to infest.
The other way green industry professionals are utilizing phenology is as a tool
to assist with marketing their plant health
care services. If there is a science of predicting the appearance of certain events,
we can use that info to coincide our messages to customers precisely at the moment
they are seeing the problem. For example, we know that customers
call tree care companies when Japanese beetles start destroying their
landscapes. We also know that Japanese beetles begin to emerge and
attack plant at 970 GDD. If we are paying attention to the GDD accumulation throughout the season, we can send our "We Treat Japanese Beetles!" mailers to our customers timed just as the first adult
beetles are beginning to munch their roses.
Phenology is an ancient practice that can help us do better tree
care today. While there are advanced tools like satellites and NIR
sensors involved, much of the science is centered on simply paying
attention to the world around us. Begin by making your own observations of natural events in your area to start seeing what happens
when. Later, you can make your own whimsical sayings to pass along
to your grandchildren.
LI
Brandon M. Gallagher Watson is director of communications at Rainbow
Treecare Scientific Advancements, and is an ISA Certified Arborist (#MN4086A).
Resources
Online
• Urban Tree Phenology Project: http://www.budburst.org/
urbantree/
• OSU's Phenology Calendar: http://oardc.osu.edu/gdd/
• National Phenology Network: https://www.usanpn.org/
Apps
• Growing Degree Days (free app that gives you your current GDD
number): https://itunes.apple.com/us/app/growing-degree-days/id38
6655475?mt=8
• PhenoMap (free app that allows you to record your own
phenological observations): https://itunes.apple.com/us/app/phenomap
/id339019580?mt=8
14 Landscape and Irrigation November/December 2013
www.landscapeirrigation.com
