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Managing Blossom End Rot in Peppers

Petrus Langenhoven, Ph.D.Horticulture and Hydroponics Crops Specialist

Illiana Vegetable Growers Symposium, Schererville IN, January 8, 2019

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Sunscald Blossom End Rot (BER)

Source: http://www.omafra.gov.on.ca/IPM/english/peppers/diseases-and-disorders/sun-scald.html

Source: http://www.omafra.gov.on.ca/IPM/english/peppers/diseases-and-disorders/blossom-end-rot.html

Blossom End Rot – A Physiological Disorder

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• Role of calcium (Ca2+) as an essential plan nutrient• Contributing to cell wall structure and strength• Important regulator of membrane structure and function

• Symptoms of Ca2+ deficiency• Symptoms usually occur early during fruit growth and development, starting as water-soaked

tissue in the blossom end region, which becomes brown, with necrotic areas at later stages• This results in dark brown and depressed lesions on the fruit surface• Fruit tissue close to the BER symptoms tends to loose green color faster than the rest of the

pepper

• Plant tissue that accumulates less Ca2+ is more susceptible to Ca2+ deficiency disorders than tissue with higher levels of Ca2+

• Ca2+ deficiency disorder symptoms in pepper are quite similar to those of tomato fruit

Blossom End Rot and Fruit Growth

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Days After AnthesisSource: F. Benoit & N. Ceustermans, 2002

BER affects fruit in early stages of development– 10 to 15 days after fruit set

Bell Pepper Fruit Growth

Blossom End Rot – When and Why?

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• BER occurs mainly during hot weather conditions

• Rate of Ca2+ supply to the fruit is lower than the rate of fruit growth

(insufficient Ca2+ is moved into actively growing cells during fruit development)

• Results in collapse of certain tissues in the fruit

• Limitation in soil Ca2+ is seldom the primary problem

• Control by soil or foliar Ca2+ application is minimally effective

Blossom End Rot – Factors that Favor BER Development

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Factors that favor BER are related to limited Ca2+ uptake and transport to the fruit• Low functional Ca levels

• Can occur during periods of fast growth• Summer/ light / high total N• N-source ratio/ too high or too low temperature and RH

• Poor Ca (water) uptake• Water stress• High salinity/root tips/ lack of O2

• Impact of other cations

• Insufficient water movement • Negative root pressure or tension due to excessive transpiration / Fluctuations (fruit/leaves)

Summary of factors affecting the uptake and distribution of Ca2+ in tomato, and the rate of fruit growth

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Adapted from: Adams P. and L.C. Ho. 1993. Effects of environment on the uptake and distribution of calcium in tomato and on the incidence of blossom-end rot. Plant and Soil 154: 127-132

Water + nutrients transport (Xylem)

Source: https://cnx.org/contents/GFy_h8cu@10.8:5aq8b3HZ@5/Transport-of-Water-and-Solutes-in-Plants

Mechanisms Regulating Calcium Deficiency Disorders – Total Tissue Ca2+ Content, Ca2+ Uptake

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• Ca2+ movement into the leaf or fruit is determined first by Ca2+

availability to the plant and root Ca2+ uptake activity• Most of the root Ca2+ uptake is believed to take place passively through

the apoplast at the root tip and lateral root growth regions where the Casparian band is not present

• Therefore, root growth enhances Ca2+ uptake by increasing the number of root tips and lateral roots

• Ca2+ moves only in the xylem to the leaves and fruit• Phloem favors the supply of K+ and to a lesser extent Mg2+ and Ca2+

• Ca2+ movement into the fruit decreases as the season progresses and phloem mobile elements such as Mg, K, P, and N increase along with the translocation of photosynthates

• Soil nutrient composition also influences root Ca2+ uptake (discussed later)

Mechanisms Regulating Calcium Deficiency Disorders – Total Tissue Ca2+ Content, Ca2+ Movement in Plant

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• After Ca2+ is taken up by the roots, it moves in the xylem vessels toward the leaves and fruit by mass flow in response to the water potential gradient generated by leaf and fruit transpiration and growth

• Mature leaves have higher transpiration rates than young leaves and fruit, which explain their higher Ca2+ accumulation

• Accordingly, low RH increases Ca2+ uptake into mature high-transpiring leaves, but reduce in low-transpiring fruit

• In addition, mature leaves receive water exclusively from the xylem, whereas young leaves and fruit receive water from both xylem and phloem vessels

• Considering that Ca2+ moves in the plant only through the xylem, water uptake from the phloem further decreases the capacity to uptake Ca2+ through the xylem sap into young leaves and fruit

Mechanisms Regulating Calcium Deficiency Disorders – Total Tissue Ca2+ Content, Plant Water Stress

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• Plant water stress has been widely reported to increase Ca2+ deficiency disorder development in both low-transpiring leaves and fruit

• Water stress, triggered by low water availability or high salinity conditions, reduce the water potential gradient between roots and low-transpiring leaves and fruit, consequently decreasing Ca2+ uptake and increasing tissue susceptibility to Ca2+ deficiency disorders

• This effect is further enhanced by Ca2+ immobility through the phloem, ensuring that the high levels of Ca2+ accumulated in older leaves are not redistributed to low-transpiring Ca2+ deficient tissues

Mechanisms Regulating Calcium Deficiency Disorders – Soil Nutrient Composition

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• Soil nutrient composition influences root Ca2+ uptake• Besides the total amount of nitrogen (N), the form of N and N source ratio

that is used can influence fruit quality• Ammonium (NH4

+) is antagonistic to Ca2+ uptake by roots• Excessive total N levels might increase fruit susceptibility to Ca2+ deficiency

disorders• High N fertilizer doses lead to substantial vegetative growth. Since Ca2+

moves with water in the transpiration stream, greater leaf area will shunt more water and Ca2+ to the leaves rather than fruit, reducing the Ca2+ content in the fruit

• N fertilization also increase fruit size

Mechanisms Regulating Calcium Deficiency Disorders – Soil Nutrient Composition, continue…

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• High salinity can reduce the accumulation of Ca2+ in the fruit, more than that of K+

• High K+, Mg2+, Na+ and NH4+ concentrations directly and indirectly depress Ca2+

uptake• NH4

+ becomes extremely harmful at high root zone temperatures, lowering Ca2+

uptake. Above 77°F, root respiration and NH4+ metabolism together consume

carbohydrates faster than is supplied from the leaves

• H2PO4- improve Ca2+ uptake (stimulate new root growth)

• NO3- stimulates Ca2+ uptake

• Al3+ depresses Ca2+ uptake

Daily Nutrient Uptake Curves for Pepper (kg/ha)

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Example:Nutrient requirement curves (kg/ha/day) for pepper cv. Maor

Soil type: SandPlant Density: 40,000 plants/acreExpected yield: 60,000 lb/acre

Source: https://www.haifa-group.com/pepper-fertilizer

1 kg/ha = 0.9 lb/acre

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Urea and soil pH

Conversions between nitrogen forms and effect on root-zone pH

15Source: Neil Mattson. 2009. Nitrogen: All forms are not equal

Effect of N source on soil pH

16Source: Zazoski, 1994

Check the label:

Potential Acidity or Basicity of fertilizer Sources

17Source: Neil Mattson. 2009. Nitrogen: All forms are not equal

18Source: https://www.ipipotash.org/udocs/eifc_no29-rf2.pdf

Source:https://www.ipipotash.org/udocs/10_Bar-

Tal_et_al_Effects_of_Fertigation_Regime_on_Blossom_End_Rot_p130-145.pdf

Nutrient solution temperatureand percentage NO3

-/NH4+

effect on percent K in thetomato plants. a. shoot; b. root

Effect of the mineral N form on K and Ca uptake by pepper plant

Effect of NO3-/NH4

+ concentration ratio on BER occurrence in tomato

Phosphorus availability affected by pH

19Source: https://www.pioneer.com/home/site/us/agronomy/phosphorus-behavior-in-soil/

K and Ca content, and K/Ca-ratio in pepper leaves related to root zone temperature

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K/Ca ratio

ROOT-ZONE TEMPERATURE (°C)

Ca

K

K/Ca

Source: Gosselin & Trudel, 1986. Root-zone temperature effects on pepper. HortScience 111(2): 220-224

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Nutrient Uptake by Bell Pepper Crop producing 50,000 lb of fruit per acre

N P2O5 K2Olbs per acre

Total plant content 200 – 260 40 – 60 240 - 320Fruit content 80 - 110 20 - 30 120 - 180

Michigan State University, Extension Bulletin E2934. Nutrient recommendation for Vegetable Crops in Michigan. http://msue.anr.msu.edu/resources/nutrient_recommendations_for_vegetable_crops_in_michigan_e2934

Plastic Film Mulches: Effect on Crop Microenvironment

22Source: Juan Carlos Dıaz-Perez. 2010. HORTSCIENCE 45(8):1196–1204

Mean root zone temperature 14 to 21 days after transplanting (DAT)

Work performed at the University of Georgia

Dry weight and stem diameter of bell pepper plants 28 DAT

23Source: Juan Carlos Dıaz-Perez. 2010. HORTSCIENCE 45(8):1196–1204

Fruit Yield of Bell Pepper Plants

24Source: Juan Carlos Dıaz-Perez. 2010. HORTSCIENCE 45(8):1196–1204

Preventative Strategies

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• Choose well adapted varieties and varieties resistant to BER• Long fruit (ie. banana and cayenne peppers)• Fruit load

• Maintain soil pH around 6.5 as shown by soil test• Do not assume that BER is sure evidence that the soil lacks calcium• Other conditions that interfere with Ca2+ uptake can cause Ca2+ to be demanded in higher

quantities than the plant can physically supply• P availability

• Use a NO3--N source (50-90%) rather than one that releases nitrogen in the NH4

+ form• Excess NH4

+ reduce Ca2+ uptake, increase BER• Also make sure that the plants are not overfertilized especially when the fruit are small• Avoid high NH4

+ levels during early fruit development• Manage soil salinity in the root zone

Preventative Strategies

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• Maintain even soil moisture• Mulches conserve moisture and moderate soil moisture extremes• Even with mulches, weekly irrigation will be necessary if there is no rain• Fluctuations in soil moisture often leads to an increase in BER• Irrigate before periods of high heat

• Mulches can increase the early season soil temperature and prevent extensive leaching of nutrients

• Make sure crop is planted in an area with good drainage• Excess water causes roots to smother, leading to reduced calcium uptake

• Healthy active roots• Do not hoe too deeply or too close to the plant

• Deep hoeing can damage roots and thereby reduce calcium uptake• Minimize damage to the roots by controlling soilborne insects and diseases

THANK YOUQuestions?

Contact details:

Dr. Petrus LangenhovenHorticulture and Hydroponics Crop Specialist

Department of Horticulture and Landscape Architecture

Purdue UniversityTel. no. 765-496-7955

Email: plangenh@purdue.edu27