February 2023 - 22

PLANT HEALTH
DESKTOP
Diagnostics
Decoding plant problems for effective management.
BY CARRIE LAPAIRE HARMON
T
here are no silver bullets or magic wands in
plant production or pest management, but we
have a wealth of information at our fingertips and
a catalog of products from which to choose. To get the best
return on our investment of time, effort and money, however,
we need accurate diagnosis for effective management.
Desktop diagnostics is all about looking at the plant and
thinking about what you know and what the plant says to
you. How do you recognize when something is wrong with
your crop? How can you figure out what to do about it?
How much can you do by yourself, and who can you call on
for backup?
WHAT'S THE PROBLEM?
In plant problem management, the first thing we have to
do is notice there is a plant problem. Once we've got that,
we need to describe the problem so we can figure out if
it is likely caused by something we humans are doing, or
something like a bug or fungus.
Then, get a little more specific if
we can so we can pick the right
management tools.
My favorite way to capture
symptoms and signs is this
little $7 magnifier that fits
nearly any phone and has a
light, so you can use it in the
shadehouse, in the truck, or
within the plant canopy. This can
22
FEBRUARY 2023 GPNMAG.COM
help you decide if that white fuzziness you are seeing is
mealybugs or fungal mycelium, which gets you halfway to
a solution - insecticide versus fungicide. Pick the wrong
one at this point and you waste money while the problem
grows unchecked. Pick the right one and you've got a good
chance of managing the plant problem.
SYMPTOMS AND SIGNS
Although these two words are often used interchangeably,
signs are evidence of the thing causing the problem -
fungal mycelium, insects, frass, sooty mold or residues.
Symptoms are the plant's way of telling us something is
wrong - wilting, yellowing, spots or rots. Plants have
a pretty limited vocabulary, though, using the same
symptoms for many different causes.
Symptoms alert us to a problem, but rarely a complete
diagnosis. Kind of like a cough might be caused by
allergies, a bacterial sinus infection, coronavirus or just
a bit too much hot sauce on your lunch. Symptoms like
yellowing or wilting might be caused by drought, flooding,
fungal root rot, bacterial stem rot or larvae chewing things
up inside the stem.
ABIOTIC VERSUS BIOTIC CAUSES
First off, we need to look at the big picture: when did
the problem start, what does it look like across the crop
and how bad is it on individual plants? This requires
you to look across the whole crop as you walk into the
greenhouse and scan for anything that just doesn't look

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February 2023

Table of Contents for the Digital Edition of February 2023

February 2023 - 1
February 2023 - 2
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February 2023 - 4
February 2023 - 5
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