Evaluation of Stress Detection Glasses
Bob Monk, Project Leader
in your plants before it's too late". This is the type of statement
used to market plant stress detection glasses. Do they work? How well do they
work? Do they have applications in Forestry?
Stress detection glasses.
The glasses are available through
several commercial outlets. The glasses are marketed to producers of crops.
They are advertised to spot, from a distance, stressed turf or field crops
due to insect, disease or moisture stress. They would be an "early warning
system" that can be used by field work crews. More recently they have
been offered in forestry supply catalogues.
The glasses are designed to block
the color green and enhance other colors. They would possibly amplify changes
(reductions) of green in the plant foliage brought about by a change in the
chlorophyll when the plant is under stress. The glasses could feasibly make
it possible to detect color changes in green that would not be visible to
the unaided eye. This would have application for determining when vegetation
is under stress and providing advanced warning so that action can be taken
to relieve that stress by watering, fertilizing, removing insects or disease,
whatever is causing the stress. It may also provide application during designation
of trees to be removed for salvage because of fire, disease or insect attack.
It may be possible with the glasses to determine, at an earlier stage, when
a tree is starting to fade. This could be very useful in the spring or early
summer when trees start to come under moisture stress and fading of crown
Normal view of tree showing
live and dead foliage.
View of same tree through stress
detection glasses. Dead/dying
foliage shows bright red.
The glasses were tested at the
San Dimas Technology and Development Center. The purpose of the testing was
to determine if plant stress could be detected with the glasses before it
could be detected with the unaided eye.
The value of the stress detection
glasses appears to be in the way they amplify a person's color perceptions.
Determining what the observations mean will take some experience by comparisons
with known plant stresses. Comparing different types of vegetation may be
difficult. Changes in vegetation that is naturally a yellowish color may be
difficult to detect. The glasses amplify color changes but give no indication
of what is causing the change. As an example, natural color changes in leaves
at the beginning of fall are significantly enhanced but the plant is probably
Some users find the glasses somewhat
disorienting or upsetting. Others seem to have no problems, at least using
them for short periods of time. The ability of the eye to detect plant stress
problems seems to increase with experience. A novice may not notice minute
changes that the seasoned veteran may think are obvious.
The glasses do appear to have utility
for forestry work. Some experience with the glasses appears to help when evaluating
what one sees. They may not provide magic answers as to whether vegetation
is about to die but they do amplify a person's perceptions. They are
a relatively inexpensive, small, and lightweight tool. They can easily be
carried to the field and can aid in quickly picking out vegetation changes.