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Excerpts
from Phone Conversation with Extension Horticulturist, January
23rd
Extension
Horticulturist:
Okay, you have described some of the basic production practices
for your cut dicentra crop. But I think I need to hear a little
more detail about the symptoms. Slight yellowing of the foliage
can be caused by a lot of things and it is difficult to diagnosis
the cause without a picture or an actual plant; even then, it
can be tough.
Maria:
Yes; I just want to pick your brain and kind of run through
the list of possibilities.
Extension
Horticulturist:
Sure. Categories of potential problems boil down to nutritional,
environmental, insect or disease, or even a combination of these.
Let’s try to rule-out some of these as causes as the starting
point to get to the bottom of what is really going on.
Maria:
Good plan. Well, the chlorosis is subtle and it isn’t
even showing on all of my plants. Extension
Horticulturist:
Do you see patterns of affected plants, for example, in one
section of the greenhouse or on one bench, or is it pretty
randomly distributed throughout the crop?
Maria:
I would say that it is random…showing on plants here
and there, but no definite pattern.
Extension
Horticulturist:
How do the roots look? To the edges of the pot? White or brownish?
Maria:
You know, I really haven’t checked the root system yet.
Extension
Horticulturist:
Do go ahead and knock several plants out of the pots to check
on the root system. Good roots grow good shoots, so you’ll
want to get in the habit of checking root systems routinely.
What about any insect problems?
Maria:
I have been scouting regularly. I put out yellow sticky
cards and do counts of what I trap on a weekly basis, even
though it can be hard to fit that into my schedule sometimes.
Fungus gnats and shore flies have been a nuisance throughout
the crop, but I’m not seeing anything else that concerns
me at this point. No thrips, whiteflies, aphids. Nothing else.
Extension
Horticulturist:
That’s all good news. Let’s talk a little more
about nutrition, then. You said that you are fertigating with
15-16-17 Peter’s Peat-Lite Special, applying 200 ppm
N…and you added no other pre-plant amendments except
for the dolomitic lime. The symptomology of chlorosis would
be consistent with deficiency of a handful of nutrients, especially
with you catching the problem this early. It’s less
likely a toxicity problem, though that’s a possibility,
as well. It’s really hard to tell when the plants are
just starting to express a problem. Do you know what your
root medium pH and Electrical Conductivity are? That information
would shed quite a bit of light on the situation.
Maria:
I haven’t run those tests on this crop, but I can do
that and get back to you.
Extension
Horticulturist:
Great! EC will give us an idea of how much fertilizer is available
to the plant; if it’s really low, that may indicate
a general nutrient deficiency that may be traced to a fertilizer
injector not working properly or something along those lines.
If the EC is very high, that may indicate salt toxicity that
has burned the roots, and when roots can’t take up nutrients,
the symptoms often manifest themselves as nutrient deficiencies.
Now pH can be a little more complicated. If it’s on
the high side, that could mean that your micronutrient cations
like Fe, Mn, Zn, and Cu are not readily available…and
Fe deficiency often appears as intervienal chlorosis of the
upper leaves. If the pH is on the low side, perhaps Mg or
Ca are beginning to be tied up. Mg deficiency often appears
as intervienal chlorosis of the lower leaves.
Maria:
Do you think that I should do anything at this point…spray
something?
Extension
Horticulturist:
Well, we really don’t have much information to go on,
at this point. We haven’t ruled out nutrition, or disease,
for that matter, as a source of the problem. You would be
fine to continue fertilizing at each watering; because the
symptoms remind me of Ca deficiency as much as anything else,
you could even apply a one-time drench of 100 ppm Ca from
CaCO3 if the pH turns out to be a little low. In
that case, even if Ca deficiency is not related to the problem,
the drench will not hurt the crop. |
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