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					BLOSSOM-END ROT                                                                                                                                                                                            Page 1

                     MANAGING BLOSSOM-END ROT                                                                                                                                                   Publication

                      IN TOMATOES AND PEPPERS                                                                                                                                                    Number
                                                                                                                                                                                                   (March 2010)
AUTHOR: Cindy Fake, Horticulture and Small Farms Advisor, Nevada & Placer Counties

B    lossom-end rot can cause
     significant crop losses in
tomatoes and peppers, especially
                                                                     BER in Tomatoes
                                                                     Susceptibility to blossom-end
                                                                                                                                                                             In terms of management,
                                                                                                                                                                             blossom-end rot is primarily
                                                                                                                                                                             a water issue. It is most severe
                                                                     rot varies among tomato
early in the season. Eggplants                                                                                                                                               following drought stress or wide
                                                                     varieties. Fast growing cultivars
may also be affected and                                                                                                                                                     fluctuations in soil moisture.
                                                                     with extensive foliage and
occasionally watermelons.                                            determinate cultivars, which set                                                                        BER is usually an early season
Symptoms                                                             all their fruit in a short period,                                                                      problem, and the first fruits are
                                                                     are frequently affected. Pear or                                                                        most severely affected. As a
                                                                     Roma tomato cultivars seem to                                                                           result, it can have significant
rot (BER) is a
                                                                     be among the most susceptible,                                                                          economic
                                                                     followed by some beefsteak and                                                                          impacts,
disorder which
                                                                     salad types. Cherry tomatoes are                                                                        as early
causes a dark,
                                                                     rarely affected.                                                                                        fruits
sunken area on the lower
(blossom) end of tomato,                                             Peppers are generally not as
pepper, and eggplant fruits. On                                      susceptible to BER as
peppers, it may also occur on                                        tomatoes, but larger, thick
the sides of the fruit, near the                                     walled varieties may be affected.
blossom-end. The discoloration                                       The disorder is not very                                                                                A number of events factor into
is usually tan, brown, or black                                      common in eggplant.                                                                                     early season blossom-end rot.
and should not be confused with                                                                                                                                              These include rapid plant
                                                                     Causes of BER
sunscald, which causes a whitish                                                                                                                                             growth, development of a large
or translucent discoloration.                                        Blossom end rot starts when the                                                                         leaf area with a high
                                                                     demand for calcium in the                                                                               transpiration rate, rapid fruit
Secondary pathogens may infect                                       expanding fruit exceeds the                                                                             enlargement, and temporary
the BER-affected area, causing                                       supply. However, it is not a case                                                                       water stresses as the weather
overall fruit rot. In dry foothill                                   of a simple calcium deficiency,                                                                         fluctuates.
summers, the area becomes dry                                        but is much more complex.
and leathery and is rarely                                                                                                                                                   Fruits in the rapid expansion
                                                                     Adding calcium to the soil rarely
infected by pathogens, leaving                                                                                                                                               phase (⅓ to ½ of full size) are
                                                                     alleviates the problem. BER
the rest of the fruit intact.                                                                                                                                                very susceptible to water stress.
                                                                     involves a low level of calcium
However, blossom-end rot is                                                                                                                                                  Even a temporary water stress
                                                                     in the fruit, but often the supply
unsightly and reduces the                                                                                                                                                    in this period can induce
                                                                     may be more than adequate in
marketability of the fruit.                                                                                                                                                  blossom-end rot because water
                                                                     the plant or soil.
                                                                                                                                                                             preferentially goes to the leaves,

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BLOSSOM-END ROT                                                                                     Page 2

reducing calcium delivery to the      the developing fruit also declines, Often, BER incidence will decline
developing fruit. High levels of      contributing to the onset of        as the season progresses, which
calcium are needed for cell           BER.                                may lead growers to believe that
growth and strong cell walls, so                                          applications of calcium have been
                                      Calcium-related plant disorders
when a rapidly expanding fruit is                                         effective. However, a reduction
                                      can also result from restricted
deficient, tissues break down,                                            in BER is more likely due to
                                      transpiration. Restricted
leaving the dry, sunken lesions       transpiration can occur when soil slowing of vegetative growth,
characteristic of blossom-end rot.                                        changes in weather, or better
                                      moisture is inadequate so the
                                                                          irrigation scheduling.
Calcium and Transpiration             plant shuts its stomata and
                                      ceases to move water. Since         Soil applications of calcium are
Calcium is a critical player in
                                      calcium moves with the              generally not very effective
blossom-end rot, but is only one
                                      transpiration stream, its           because BER is seldom induced
of several factors (Taylor et al.
                                      movement also stops.                by soil calcium deficiency. UC
2004). Calcium is dissolved in the
                                      Transpiration can also be           researchers have shown that
soil solution, taken up by plant
                                      restricted in cool or cloudy        most California soils contain
roots, and then moves through
                                      weather because the atmospheric     adequate plant-available calcium
the xylem from the roots to the
                                      demand for moisture is low.         and that commonly used soil
                                      Thus, early plantings of            tests systematically
Calcium only
                                      tomatoes, especially those          underestimate calcium in the soil
moves with
                                      planted into cold soil, are often   solution. The most common test
water in the
                                      subject to blossom-end rot.         for soil calcium, an ammonium
xylem, it
                                                                          acetate extraction, actually
does not                              The Role of Other Nutrients
                                                                          provides almost no information
move in the                           A calcium deficiency in the fruit about calcium availability to the
phloem.                               may also result from other          plant. A saturated paste
Under conditions of high              factors. Excess nitrogen            extraction is a better test, but it
evaporative demand, i.e. low          stimulates vegetative growth,       still underestimates calcium in
relative humidity and high            increasing the leaf area and thus the soil solution by a factor of 5
temperature, water moves              the amount of transpiration from (Hartz et al. 2007.).
rapidly to the leaves, where most     leaves. Potassium (K),
transpiration occurs. The calcium     magnesium (Mg) and ammonium Foliar applications of calcium are
                                                                          also unlikely to affect blossom-
is carried along with the water, so   -nitrogen (NH4-N) all compete
most calcium absorbed by the          with calcium for uptake into the end rot incidence. In the plant,
plant ends up in the leaves. Fruit    plant, so high concentrations of calcium only moves with water in
                                                                          the xylem. It has no ability to
do not transpire as much as           those nutrients may reduce the
                                                                          move through the phloem from
leaves; therefore less calcium        amount of calcium available in
                                                                          leaves to fruit, thus it cannot
reaches the fruit, which can cause    the fruit.
                                                                          move from the application site to
a localized calcium deficiency.       Because of the perception that      the fruit where it is needed.
The transpiration rate of the         BER is an overall calcium
fruit is further reduced after the    deficiency, many growers add
waxy cuticle develops, when the       calcium to the soil or apply foliar
fruit is about ½-¾” in diameter.      calcium. This rarely has an
With decreased transpiration, the     impact on the disorder, but does
amount of calcium moving into         add to the cost of production.

BLOSSOM-END ROT                                                                                     Page 3

Managing Blossom-end Rot               temperatures and                     References
                                       evaporation, thus moderating
Blossom-end rot can be                                                      Bell Pepper Production in
                                       soil moisture fluctuations.
prevented with good soil                                                       California. 2008. Tim
management and careful               5. Avoid cultivating close to             Hartz, et al. UC ANR
monitoring of soil moisture so as       plants so as to prevent feeder         Publication #7217. http://
to limit stress.                        root damage that may restrict
                                        water flow during hot periods.         docs/7217.pdf
                                                                            Blossom-end rot: A calcium
                                     6. Calibrate nitrogen                     deficiency. 2004. Taylor,
                                        applications to actual plant           M.D. and S.J. Locascio. J.
                                        use. Avoid over-fertilizing as         Plant Nutr. 27(1):123-139.
                                        rapid plant growth induced
                                        by high N can contribute to         Blossom-end rot and
                                        BER. Tomatoes use a                    Calcium Nutrition of
                                        maximum of about 200                   Pepper and Tomato. 2009.
Strategies to Reduce                    pounds of nitrogen per acre.           J. Mayfield and W. Kelley.
Blossom-end Rot                         Depending on soil, and                 The University of Georgia
                                        environmental conditions,              Cooperative Extension.
1. Cover crop or incorporate                                         
                                        less may be appropriate.
   compost to increase soil                                                    caespubs/pubcd/C938/
   organic matter and diminish       7. Use nitrate forms of nitrogen          C938.html
   soil moisture fluctuations,          rather than ammonium.
   especially in decomposed                                                 Blossom-end rot incidence of
                                        Excess ammonium in soils               tomato as affected by
   granite soils.                       reduces calcium uptake and             irrigation quantity,
                                        may exacerbate blossom-end             calcium source, and
2. Use tensiometers or matrix
                                        rot.                                   reduced potassium. 2004.
   blocks to monitor soil
   moisture. Do not allow soil to                                              Taylor, M.D., Locascio, S.J.,
                                     8. Unless soil tests clearly
   completely dry out when                                                     and M.R. Alligood.
                                        indicate calcium deficiency in
   tomato fruit are expanding                                                  Hortscience 39(5):1110-
                                        your soil, soil applications of
   rapidly. Schedule irrigations                                               1115.
                                        calcium will probably not
   to maintain moist, but not           reduce the problem. If you          Blossom End Rot of Tomato.
   wet, soil conditions. For            have a high magnesium soil             Vegetable Crop Fact Sheet
   determinate cultivars, once          (and a pH below 6.5), liming           735. 1979. A. Sherf and T.
   the fruit are more than half of      may be useful to increase the          Woods. Cooperative
   full size, some water stress         ratio of calcium ions to other         Extension, New York State,
   can be tolerated and will            competitive ions in the soil.          Cornell University. http://
   improve flavor.                                                             vegetablemdonline.ppath.cor
                                     9. Foliar applications of calcium
3. Reduce plant stress by               are of little value as calcium is      Tomato_BlossRt.htm
   irrigating before periods of         poorly absorbed by leaves
   high heat.                           and does not move easily in         Blossom end rot of tomato.
                                        the plant.                             2000. Hansen, M.A.
4. Use organic mulch along                                                     Publication 450-703W.
   plant rows to reduce soil                                                   Virginia Cooperative

BLOSSOM-END ROT                                                                   Page 4

   Extension Plant Disease             mag/farming_no_easy_fixes/
   Factsheets. http://              Soil Calcium Status Unrelated to             Tipburn of Romaine Lettuce.
   703/450-703.html                     2007. Hartz ,Timothy K. et
Blossom-End Rot of Tomato,              al. HortScience 42 (7):1681-
   Pepper, and Eggplant.                1684.
   Factsheet HYG-3117-96. S.
   Miller, R. Rowe, & R. Riedel.
   The Ohio State University
   Extension. http:/ohioline.osu.
Blossom-End Rot of Tomato,
   Pepper, and Watermelon.
   2000. Charles W Averre and
   P. B. Shoemaker. North
   Carolina Cooperative
   Extension Service. http://

Blossom End Rot of Tomatoes
   and Other Vegetables.
   2002. Martin A. Draper,
   Rhoda Burrows, and Steven
   Munk. South Dakota
   Extension Fact Sheet 909.
Effects of environment on the
   uptake and distribution of
   calcium in tomato and on the
   incidence of blossom-end rot,
   pp. 583-588. 1993. Adams, P.
   and L.C. Ho. IN: M.A.C.
   Fragoso and M.L. van
   Beusichem (eds.)
   Optimization of plant
   nutrition. Kluwer Academic
   Publishers, Netherlands.
No easy fixes seen for vegetable
   calcium disorders. 2006. Dan
   Bryant. Western Farm Press.


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