Using The Plant Disorder Diagnostic Key

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Using The Plant Disorder Diagnostic Key

• By Paul A. Thomas, and Bodie V. Pennisi
• Department of Horticulture,
• College Of Agricultural and Environmental Sciences

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High Heat, Low Fertility, High IrrigationHigh
Light LevelsDry Winds
Theres Always More Than One Problem !
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Unopened Buds
Temperature Humidity Light levels Natural
Gas Insecticides Manganese Mites Thrips
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Fully Opened Flowers
Temperature Humidity Light levels Insecticides Nat
ural Gas Botrytis Virus
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Growing Meristem
Boron Calcium Ethylene Natural Gas Cyclamen
mites Thrips
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New / Soft Growth
Trace Elements Nickel Calcium Light
Levels Cyclamen mites Thrips Propane Natural
Gas Herbicides
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Newly Matured Leaves
Temperature Humidity Light levels Potassium Phosph
orus
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Mature/Older Leaves
Temperature Humidity Light levels Spacing Nitrogen
Phosphorus Magnesium Potassium Fluoride
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Whole Plant Disorder
Temperature Humidity Light levels Spacing Nitrogen
Soil pH Sloil EC
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Below Soil Disorder
Temperature Humidity Light Levels Disease Drought
Anoxia Insects
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General Disorders
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Using The Plant Diagnostic Key
A diagnostic key is a tool used to
differentiate between many possible, yet similar
looking symptoms. Diagnostic keys are simple to
use, and can significantly speed up the diagnosis
process. However, no key can replace actual
diagnostic testing. Always test to verify
assumptions before implementing any treatments.
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Using The Diagnostic Key
The diagnostician must first decide how to
describe the problem. Several descriptive
words should be written down prior to reviewing
the many choices provided in the key.
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Using The Diagnostic Key
Cleared Tissue Blackening Dessicated
Wilted Shiny
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There are several categories or approaches to
choose from, depending on the extent of the
problem, or the plant parts that are expressing
symptoms of a disorder.
Problems Involving ENTIRE Crop With or Without
Pattern Problems Involving WHOLE PLANT With
Normal Shape Leaves And Stems. Problems That
Appear To Primarily Involving LEAVES, Secondarily
Flowers Problems Involving FLOWERS Problems
Involving ROOT SYSTEMS
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Under each category, there are several choices
to choose from.
Problems That Appear to Primarily Involve LEAVES
and to a Lesser Extent, Flowers. A. LEAF
SHAPE ABNORMAL, twisted, or physically damaged
stems, internodes normal. AA . LEAF SHAPE
NORMAL, internode length normal, but leaves
off-color, cleared or have spots. AAA LEAF
SHAPE NORMAL, however, stem internodes are very
long or very short. AAAA Leaf shape normal, stem
internodes normal. Stems severed / broken at
soil line. AAAAA. Leaf puckered or with
expanded cells, galls, thickening of epidermis.

The three sub-choices are marked A, AA , and AAA
as they are all related to the category,
however, they denote different possibilities from
which we may decide on the best fit to our
described symptoms. Underneath AA are the next
level of choices.
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These additional choices, marked B, and BB,
allow us to further refine our choices, and
focus in on the problem.
AA . LEAF SHAPE NORMAL, internode length normal,
but leaves off-color, cleared or have
spots. B. Leaf color in a small portion of
the leaf is abnormal. BB. Leaf color over a
majority of the leaf surface is abnormal.
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AA . Leaves appear normal shape, discrete parts
of plant are off-color, cleared or wilted. BB.
Leaf color over a majority of the leaf surface
is abnormal. C. Entire plant pale
green, poor growth with some marginal
Fungicides, Herbicides
yellow at the margins, few blooms, small
flowers. Nutritional Deficiencies (Check
roots for damage.) CC. Entire plant or
most leaves yellow, with central portions
of the leaf strongly affected. Tissue
dies within 3 to 10 days. Herbicides /
Sunscald CCC. Entire plant or most leaves
turn dark black-green, semi Surfactant / Soaps
transparent to light, wilt, then
die within 48 hours. Chlorine, Petroleum
fuels)
Next, we note the best fit sub-category.
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AA . Leaves appear normal shape, discrete parts
of plant are off-color, cleared or wilted.
BB. Leaf color over a majority of the leaf
surface is abnormal. C. Entire plant
pale green, poor growth with some marginal
Fungicides, Herbicides
yellow at the margins, few blooms, small
flowers. Nutritional Deficiencies (Check
roots for damage.) CC. Entire plant or
most leaves yellow, with central portions
of the leaf strongly affected. Tissue
dies within 3 to 10 days. Herbicides /
Sunscald CCC. Entire plant or most leaves
turn dark black-green, semi Surfactant / Soaps
transparent to light, wilt, then
die within 48 hours. Chlorine, Petroleum fuels)

Next, we note the best fit possibilities That
we should look into.
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BB. Leaf color over a majority of the leaf
surface is abnormal. C. Entire plant
pale green, poor growth with some marginal
Fungicides, Herbicides yellow at
the margins, few blooms, small
flowers. Nutritional Deficiencies (Also
Check roots for damage.) CC. Entire
plant or most leaves yellow, with central
portions of the leaf affected.
often dies within 3 to 10 days. Herbicides /
Sunscald CCC. Entire plant or many leaves
turn dark black-green, semi Surfactant / Soaps,
transparent to light, then die
within 48 hours. Oils, Chlorine, Petroleum
Occasionally, the diagnostician is directed to
check additional areas as many plant
problems have more than one cause.
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Nutritional Disorders
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Plant Nutrient Functions, Deficiency and
Toxicity Symptoms
Nutrient Management Self-Study Course
Nutrient Management Self-Study Course
Nutrient Management Self-Study Course
http//www.montana.edu/wwwpb/pubs/mt4449.html9
An Excellent Publication!
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Nitrogen
Entire plant light green or yellow. No necrotic
spotting or striping
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• Phosphorus

Purple or reddish discoloration. Prominent on
undersides. Leaves slightly smaller, darker
green.
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• Potassium

No interveinal chlorosis, Chlorotic areas with
burnt leaf margins, or spottong along leaf
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• Calcium

Young leaves increasingly smaller, bunched,
hooked may turn brown and die back. Buds may or
may not be affected
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• Magnesium

General chlorosis with interveinal
chlorosis Leaves sometimes have red, yellow or
necrotic spots.
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• Sulfur

Young leaves light green. No chlorotic spotting
or striping
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• Boron

New growth twisted, bunched up. Leaves thicker,
rolled or stiffened, brittle. Meristem dies back
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• Nickel

Mouse Ear or dwarf leaves. Some darkening of
the leaf. Crinkled leaves.
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• Iron

Sharp interveinal chlorosis. Leaves full size.
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• Manganese

Interveinal chlorosis. Stunted growth. Necrotic
spots.
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• Molybdenum

Pale, light green leaves Leaves scorched, rolled
or twisted
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• Zinc

Middle leaves with interveinal chlorosis.
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• Copper

Yellow leaves. Tips of leaves withered. Leaf
tips eventually die.
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Chloride
No interveinal chlorosis, Chlorotic and
necrotic lesions with abrupt boundary between
dead and living tissue
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So how do we really know?
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Soil Analysis N as NH4 20 or less (avoid
above 40 ppm N as NO3- 160 - 60
ppm Element Parts per Million P 30 - 5 ppm
- lower is better! K 200 - 40 ppm Ca 160 - 40
ppm Mg 100 - 60 ppm S 75 - 100 ppm Fe 0.3 -
3.0 ppm Mn 0.1 - 3.0 ppm Zn 0.1 - 3.0
ppm Cu 0.1 - 0.3 ppm B 0.05 - 0.5 ppm
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Foliar Analysis Percentage N 2.72 - 6.28 P 0.28
- 0.64 K 1.88 - 3.48 Zn 30 51 Ca 0.93 -
1.13 Parts Per Million Cu 6 16 Mg 0.32 -
0.78 Mn 135 302 Fe 72 277 B 21 49 S 0.22 -
0.50 Mo 0.14 - 0.46 Na 0.01 - 0.156 Al 34 - 136
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Fixing Deficiencies
Post-planting amendments for common
deficiencies Material Rate ( Oz /
100 gal of water) Magnesium sulfate 32 oz.
Every 3 weeks Calcium nitrate 32 oz. Every
3 weeks Iron sulfate 1.0 oz. 1 application
Excess can cause leaf spotting and problems
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Form Of Nitrogen Affects Growth of Roots
20-20-20
NO3
NH4
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High Temperature Effect
100 ppm
90oF
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Thank You !
Nutrient Management Self-Study Course
Nutrient Management Self-Study Course
Nutrient Management Self-Study Course
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Lets Take A Test !
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2,4-D on Salvia

• 3 d after exposure

• 11 d after exposure

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2,4-D on Salvia

• 3 d after exposure

• 11 d after exposure

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2,4-D on Salvia

• 3 d after exposure

• 11 d after exposure

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Excess Ammonia Nitrogen
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Mottle Pansy Syndrome
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Some Examples