Nutrient Deficiencies of Calibrachoa


By John M. Dole, Amy Williams, James L. Gibson, Brian E. Whipker, Paul V. Nelson, Brenda R. Cleveland and F.R. Walls

Fertility monitoring and management for Calibrachoa requires a balancing of the plant's needs. Growers must be aware and manage the root substrate pH, electrical conductivity (EC) and provide adequate, but not excessive, levels of all essential elements.

Nutrient deficiency descriptions are unavailable for most floriculture crops, yet growers must often make quick diagnoses. A research project initiated at North Carolina State University in Raleigh documented deficiency symptoms in vegetatively-propagated Calibrachoa 'Pure White' to assist growers. Using a plant diagnostic lab to identify the source of problems is still the best way to ensure accurate diagnoses, since many nutritional, physiological, insect and disease problems can mimic each other.

Disclainer: Growers should read and follow all label directions. Test the corrective procedure on a small number of plants prior to applying it to the entire crop.

Macronutrients · Micronutrients

Macronutrients
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Description

Possible Causes and Management
Nitrogen (N) (top)
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Initially, nitrogen-deficient plants are smaller and express a light green color when compared to the control.

Low Substrate Nitrogen
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As symptoms progress the plant becomes severely stunted and has an upright architecture.

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Advanced symptoms include smaller uniformly chlorotic young and recently mature leaves and lower leaf yellowing.

Phosphorus (P) (top)
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Phosphorus-deficient plants are pale green in color and initially develop small tan to brown necrotic spots on the young and recently mature leaves.

Low Substrate Phosphorus
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Plants are compact and have less axillary branching. The lower mature leaves are chlorotic and are progressing into necrosis.

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Under advanced symptoms, chlorotic mature leaves exhibit random brown necrotic patches.

Potassium (K) (top)
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Potassium-deficiency is observed as a yellowing of the lower mature leaves, which begins at the leaf tips and progresses to the base.

Low Substrate Potassium
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The upper and lower mature leaves are cupped and curl downward compared to the control.

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As symptoms progress the mid to upper mature leaves of the shoot tip form small brown necrotic patches at the leaf base.

Calcium (Ca) (top)
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Light green interveinal chlorosis of the young to mature leaves is the initial symptom of calcium-deficiency.

Low Substrate Calcium
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Axillary shoot development and leaf expansion is less and the plant appears stunted.

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Leaf comparison of chlorotic calcium-deficient leaves and control leaves: calcium-deficient leaves are smaller and cupped inward compared to the control leaves.

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Chlorotic shoots turn light yellow and the young leaves develop a brown necrosis on the tips. Bud abortion and flower inhibition are common symptoms with calcium deficiency.

Magnesium (Mg) (top)
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Initial magnesium-deficient symptoms show that the young and recently mature leaves are light green and appear slightly enlarged when compared to the control.

Low Substrate Magnesium
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As symptoms progress a distinct chlorosis appears on the recently mature and mature leaves. The margins are light green while the midrib remains a dark green.

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Advanced symptoms show random tan necrotic spots appearing on the chlorotic mature leaves.

Click for Larger Image Chlorotic leaves have a slightly swollen appearance and are curling downward as compared to the control.
Sulfur (S) (top)
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Sulfur deficient plants are small and uniformly chlorotic when compared to the control.

Low Substrate Sulfur
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Shoot elongation is less and the plants are stiff and compact. The young and recently mature leaves are a lime green color when compared to the control.

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Overall leaf size is slightly smaller and chlorotic leaves begin to develop tip necrosis.

Micronutrients (top)
Photograph

Description

Possible Causes and Management
Boron (B) (top)
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Initially, young leaves of boron-deficient plants become deformed and chlorotic.

Low Substrate Boron
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A yellow-green interveinal chlorosis progresses down the shoot affecting the young to the mature leaves.

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At the advanced stage a severe interveinal chlorosis develops and lateral shoots are minute. Recently mature leaves turn to a brown papery necrosis and eventually fall off.

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Boron-deficient shoots are short and rigid with leathery leaves when compared to the control. Flowering is less and bud abortion often occurs.

Copper (Cu) (top)
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The shoot apex of copper-deficient plants remains unfurled and the young leaves fold inwards, giving the shoot tip a tight compact appearance.

Low Substrate Copper
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A close-up of chlorotic shoot tip under advanced symptoms shows extreme leaf folding. The young and recently mature leaves also appear narrower than the control.

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At the advanced stage copper-deficient plants are stunted with little axillary shoot development.

Iron (Fe) (top)
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Symptoms develop rapidly as the young leaves and recently mature leaves turn a light green color.

Low Substrate Iron
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As symptoms progress, the mature leaves remain dark green while the young and recently mature leaves become evidently more chlorotic.

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A yellow-green chlorosis progresses down the plant and the affected leaves begin to fold inward and curve at the base. The youngest leaves have turned brown and necrotic.

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Eventually the young chlorotic leaves turn white then ultimately develop necrosis.

Manganese (Mn) (top)
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Initial manganese-deficiency shows the young leaves with a faint chlorosis. Overall the entire plant is a dull light green.

Low Substrate Manganese
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Recently mature to mature leaves twist and roll under at the margins and are a lighter green color compared to the control.

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A tan-white necrosis affects the leaf margins of the mature leaves and eventually develops over the entire leaf.

Click for Larger Image Necrotic spots appear on the young leaves of the axillary shoot tips.
Click for Larger Image Manganese deficiency is more pronounced in the middle of the shoot as the recently mature leaves shrivels and senesce causing the shoot to appear thin and spindly.
Zinc (Zn) (top)
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Zinc-deficient plants have chlorotic deformed shoot tips.

Low Substrate Zinc
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As symptoms progress, the youngest to recently mature leaves develop patches of brown spots in the middle of the leaves. The necrosis moves from the margin inward. The affected leaves also have a random yellow-green chlorosis, curl downward and fold inward.

Click for Larger Image A comparison of chlorotic and necrotic leaves to the control.

Amy L. Williams, Dharmalingam S. Pitchay and James L. Gibson are graduate research assistants, Paul V. Nelson is professor in floriculture, John Dole is associate professor in floriculture, and Brian E. Whipker is assistant professor in floriculture at North Carolina State University, Department of Horticultural Science, Box 7609, Raleigh, NC 27695-7609. Brenda R. Cleveland is agronomist and F.R. Walls is assistant director, Agronomic Division of North Carolina Department of Agriculture. The authors thank Paul Ecke Ranch, Encinitas, Calif., Tom Abramowski, Rockwell Farms, Rockwell, N.C., and the North Carolina Commercial Flower Growers' for grant support, Paul Ecke Ranch for supplying the vegetative cuttings and Smithers-Oasis for supplying the propagation medium. The images and corrective procedures can be viewed at http://www.ces.ncsu.edu/floriculture.

Disclainer: Growers should read and follow all label directions. Test the corrective procedure on a small number of plants prior to applying it to the entire crop.

© Copyright NC State University, 2002

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