Using The Plant Disorder Diagnostic Key

By Paul A. Thomas, and Bodie V. Pennisi Department of Horticulture,

College Of Agricultural and Environmental Sciences

High Heat, Low Fertility, High IrrigationHigh Light LevelsDry Winds

There’s Always More Than One Problem !

Unopened Buds

TemperatureHumidity

Light levelsNatural GasInsecticidesManganese

MitesThrips

Fully Opened FlowersTemperature

HumidityLight levelsInsecticidesNatural Gas

BotrytisVirus

Growing Meristem

BoronCalciumEthylene

Natural GasCyclamen mites

Thrips

New / Soft Growth

Trace ElementsNickel

CalciumLight Levels

Cyclamen mitesThrips

PropaneNatural GasHerbicides

Newly Matured Leaves

TemperatureHumidity

Light levelsPotassium

Phosphorus

Mature/Older Leaves

TemperatureHumidity

Light levelsSpacingNitrogen

PhosphorusMagnesiumPotassiumFluoride

Whole PlantDisorder

TemperatureHumidity

Light levelsSpacingNitrogenSoil pHSloil EC

Below Soil Disorder

TemperatureHumidity

Light LevelsDiseaseDroughtAnoxiaInsects

General Disorders

Using The Plant Diagnostic Key

A diagnostic key is a tool used to differentiatebetween many possible, yet similar looking symptoms.

Diagnostic keys are simple to use, and can significantlyspeed up the diagnosis process.

However, no key can replace actual diagnostic testing.Always test to verify assumptions before implementingany treatments.

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 choicesprovided in the key.

Using The Diagnostic Key

Cleared Tissue

Blackening

Dessicated

Wilted

Shiny

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

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 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.

Under each category, there are several choices to choose from.

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.

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.

These additional choices, marked B, and BB, allow us to further refine our choices, and focus in on the problem.

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 thebest fit sub-category.

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 thebest fit possibilitiesThat we should look into.

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 diagnosticianis directed to check additionalareas as many plant problemshave more than one cause.

Nutritional Disorders

http://www.montana.edu/wwwpb/pubs/mt4449.html#9

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An Excellent Publication!

Plant Nutrient Functions, Deficiency and

Toxicity Symptoms

Nitrogen

Entire plant light green or yellow.

No necrotic spotting or striping

Phosphorus

Purple or reddishdiscoloration.

Prominent on undersides.

Leaves slightly smaller, darker green.

Potassium

No interveinal chlorosis,

Chlorotic areas with burnt leaf margins, or spottong along leaf

CalciumYoung leaves increasingly smaller, bunched, hooked may turn brown and die back.

Buds may or may not be affected

Magnesium

General chlorosis with interveinal chlorosis

Leaves sometimes have red, yellow or necrotic spots.

Sulfur

Young leaves light green.

No chlorotic spotting or striping

Boron

New growth twisted,

bunched up.

Leaves thicker, rolled

or stiffened, brittle.

Meristem dies back

NickelMouse Ear or dwarf leaves.

Some darkening of the leaf.

Crinkled leaves.

IronSharp interveinal chlorosis.

Leaves full size.

Manganese

Interveinal chlorosis.

Stunted growth.

Necrotic spots.

Molybdenum

Pale, light green

leaves

Leaves scorched,

rolled or twisted

Zinc

Middle leaves

with interveinal

chlorosis.

Copper

Yellow leaves.

Tips of leaves withered.

Leaf tipseventuallydie.

Chloride

No interveinal chlorosis,

Chlorotic and necrotic lesions with abrupt boundary between dead and living tissue

So how do we really know?

Soil AnalysisN 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 ppmCa 160 - 40 ppmMg 100 - 60 ppmS 75 - 100 ppm Fe 0.3 - 3.0 ppmMn 0.1 - 3.0 ppmZn 0.1 - 3.0 ppmCu 0.1 - 0.3 ppmB 0.05 - 0.5 ppm

Foliar AnalysisPercentage

N 2.72 - 6.28P 0.28 - 0.64K 1.88 - 3.48Zn 30 – 51Ca 0.93 - 1.13

Parts Per MillionCu 6 – 16Mg 0.32 - 0.78Mn 135 – 302Fe 72 – 277B 21 – 49S 0.22 - 0.50Mo 0.14 - 0.46Na 0.01 - 0.156Al 34 - 136

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

Form Of NitrogenAffects Growth of Roots

20-20-20NO3 NH4

100 ppm

90oF

High Temperature Effect

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Lets Take A Test !

2,4-D on Salvia

• 3 d after exposure • 11 d after exposure

2,4-D on Salvia

• 3 d after exposure • 11 d after exposure

2,4-D on Salvia

• 3 d after exposure • 11 d after exposure

Excess Ammonia Nitrogen

Mottle Pansy Syndrome

Some Examples