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Physiological, Nutritional and Other Disorders of Tomato Fruit
The Tomato Magazine
April 2007
By Stephen M. Olson
University of Florida
Blossom-end Rot
Blossom-end rot (BER) is caused by a
localized Ca defi ciency in developing fruit.
It begins with light tan, water-soaked areas
which can then enlarge and turn black and
leathery in appearance. Most often the problem
occurs at the blossom end of the fruit,
but on occasion can occur on the side. It may
also occur internally with no visible symptoms
on outside of the fruit.
Many factors can influence BER. The
following conditions may increase BER:
low soil Ca, high N rates, using ammoniacal
sources of N, high concentrations of soluble
K and Mg in the soil, high salinity, low
humidity, inadequate soil moisture, damage
to root system by nematodes, disease or
mechanical means or heavy pruning.
In greenhouse production, not cycling
the irrigation system at night can increase
BER, since night is an important time for
Ca uptake. In Florida, adequate soil Ca
is considered to be 300 ppm or higher by
the Mehlich-1 index. Foliar applications
of Ca materials have not proven to reduce
BER since very little Ca is taken up by the
fruit and that taken up by the leaves cannot
be translocated to the fruit. Control is
through proper fertilization and good water
management
.
Catface
Catfacing is a generic term used to
describe a tomato fruit that has a gross
deformity and is usually not marketable.
The defect is usually located on the blossom
end of the fruit. The deformity caused by
something (internal or external) that
occurs during the formation of the
flower that results in the fruit not
developing normally.
There is little published information
as to the exact cause, and there
actually may be more than a single
cause. Cool or cold temperatures that
occur about three weeks before bloom
can increase the amount of catfacing.
In general, jointless varieties are more
prone to catfacing than jointed varieties.Heavy pruning in indeterminate
varieties has shown
to increase catfacing,
but this has not shown
to happen in our short-stake
varieties.
In indeterminate varieties,
this is thought to be related
to reduction in auxins in the
plant from removing the
growing points. Drifts of
herbicides such as 2,4-D can
cause fruit to catface. Heavy
thrips feeding on young fruit
can cause a type of catfacing.
Also, fruit on plants that are
mildly affected by
little leaf (see EDIS Publication HS-883 for
more information) are severely catfaced.
There is no known control.
Varieties should be selected that historically
have had little problems for catfacing.
Try to prevent spray drift from undesirable
chemicals and, in the case of little leaf, prevent
soils from becoming waterlogged.
Cracking
Two different forms of cracking occur
in tomato fruit. Radial cracking originates
from the stem end and progresses toward the
blossom end. Concentric cracking occurs in
a ring or rings around the stem scar. It is possible
to have both types on the same fruit.
Cracking occurs when the internal
expansion is faster than the expansion of
the epidermis and the epidermis splits.
Varieties differ greatly in their susceptibility
to cracking. Cracking can occur at all stages
of fruit growth but as fruit matures they
become more susceptible, especially as color
develops.
The more resistant a variety is, the
later in maturity of the fruit cracking may
occur. Control is through selecting tolerant
varieties or by reducing fl uctuations in soil
moisture. Cracking may also be reduced
by maintaining a good foliage cover, since
exposed fruit are more susceptible. Wide f uctuation in air temperature
can also
increase cracking. Cracking is more of a
problem in a vine-ripe versus a mature green
operation.
Graywall (blotchy ripening)
Internally, graywall is characterized by
dark necrotic areas usually in the vascular
tissue of the outer walls. The necrosis is
sometimes present in the cross-walls and
very infrequently in the center pith area of
the fruit. Outward symptoms show up as
grayish appearance caused by partial collapse
of the wall tissue, hence the term graywall.
It typically develops on green fruit prior to
harvest but can show up later. Fruit affected
are typically not marketable due to blotchy
appearance as fruit ripens. Cause is not completely
understood. There are varieties differences
in susceptibility. Graywall is more of a
problem during cool and short days. High N
may increase problems, and adequate K may
reduce the problem.
Internal White Tissue
Fruit affected by this disorder usually
show no outward symptoms. When ripe
fruit are cut, white hard areas, especially in
the vascular region, are present in the outer
walls. Under severe conditions, fruit may
also show white tissue in and cross-wall and
center of the fruit. The problem is more of a
concern with vine-ripe or u-pick producers
since fruit picked mature-green and gassed
rarely show the problem. High temperatures
during the ripening period in the fi eld
seem to trigger the problem. Adequate K
fertilization has shown to reduce but may not
eliminate it. Some varieties are more resistant
to the problem, especially the high-colored
varieties. At times, the problem may be so
severe that the fruit are unmarketable.
Irregular Ripening
Irregular ripening is a fruit ripening
disorder caused by feeding of nymphs of the
Silverleaf whitefl y [Bemisia tabaci B-biotype
(argentifolii)] on the tomato foliage. Green
fruit show no symptoms but as fruit ripens,
color fails to develop uniformly. Color often
develops along locule walls with intermediate
areas remaining green or yellow, producing
a star-burst appearance. With sufficient time,
nearly normal external color develops on
most fruit but internal areas remain hard with
little or no color development. Fruit affected
are unmarketable. Irregular ripening can
occur with as few as four Silverleaf whitefl y
nymphs per terminal leaf. This disorder
can be controlled if nymphs are controlled. Silverleaf whiteflies get
their name from
damage they do to foliage of squash plants.
Pox and Fleck
In most cases when a fruit is affected
both disorders are found together but are
considered separate problems. Pox is
described as small cuticular disruptions
found at random on the fruit surface. The
number can vary from a few to many. Fleck,
also known as Gold Fleck, shows up as small
irregular shaped green spots at random on
the surface of immature fruit which turn to
a gold color as fruit ripens. Number of spots
can vary from few to many. Fruit severely
affected with pox and fl eck is not marketable.
Both conditions seem to be genetic in nature,
but are difficult to breed out of a variety
since the conditions only show up under
certain environmental conditions. There
seems to be some differences of opinion as
to the conditions for the problem to show up.
There are differences between varieties as to
susceptibility to pox and fleck.
Puffiness
When this problem is slight, it may be
impossible to detect puffi ness until fruit are
cut. Severe puffy fruit will appear to be flat
sided or angular in nature. When fruit are
cut, open cavities open cavities re observed
between the seed gel area and the outer wall.
Fruit are also very light in relation to Size.
This problem is caused by any
factor that affects fruit set. This
can be due to inadequate pollination,
fertilization or seed
development. Most common
causes in Florida are too low
or high of temperatures during
fruit set. Use of “hot set” varieties
can reduce the problem but
even these have limitations when
night temperatures get above
about 75°F. Other factors such as high N, low
light or rainy conditions can also cause seed
set problems.
Rain Check
Rain check can be described as tiny
cracks that develop on the shoulder of the
fruit. These cracks can vary from just a few
to almost complete coverage of the shoulder.
The cracks feel rough to the touch and
affected areas can take on a leathery appearance
and not develop proper color as fruit
ripens. Green fruit are most susceptible,
followed by breakers and ripe fruit are not
affected at all. Damage occurs most often on
exposed fruit after a rain. Exact cause is not
known, but appears to be related to exposure
of the fruit to water. Problem is more severe
when heavy rains occur after a long dry
period. There are differences among varieties
to susceptibility to rain check. Also, varieties
with good leaf coverage usually have less
rain check.
Sunscald
Sunscald can be broken down into two
types, sub lethal and lethal. Sub lethal
sunscald can be described as a yellow, hard
area usually on the shoulder of the fruit.
Note fl atten areas on sidewalls of fruit.
This occurs when tissue temperatures
rise above about 86° F. The high tissue
temperatures will not allow the red pigment
to develop nor flesh to soften but allows
the yellow pigments to develop. With lethal
sunscald, the tissue turns white and dies.
Many times the dead tissue will turn black
from fungi that are feeding on the dead
tissue. Lethal sunscald occurs when tissue
temperatures rise above 104° F. Damage
usually occurs when fruit are suddenly
exposed to sunlight. This most frequently
occurs after a harvest or a storm when leaves are moved around and fruit
exposed. Over
pruning can also increase sunscald problems
especially with fruit in the upper part of the
plant. Also good spray programs to ensure
good foliage cover can reduce problems.
Growers at times may use a sun screen
material such as Snow or Surround to help
reduce sunscald.
Tomato Spotted Wilt Fruit Damage
When infection is early in season, fruit
fail to set or are severely deformed and may
have cracks or concentric rings on fruit. If
disease hits later in the season it may be
impossible to see any damage on green fruit,
but after ripening, yellow rings or blotches
may show up rendering the fruit unmarketable.
This is a severe problem when fruit are picked mature green, gassed and shipped out, since the discoloration may not show up until it reaches terminal market and load is rejected because of discolored fruit. The discoloration is only on the surface and center of fruit will ripen normally. Control of fruit problems is through control of virus of vector. Research has shown that control of primary infection is not possible with insecticides but control of secondary infection is possible through good spray schedule and selection of materials that will control thrips. Recent research has shown that primary infection can be reduced with production on highly UV-refl ective (metalized) mulches and use of Actigard in production system. Resistant varieties are available but at times the foliage may not show symptoms but the fruit may, rendering it unmarketable.
Western Flower Thrips Oviposition Damage
This injury is characterized by a small
dimple often with a white halo around the
dimple. The injury is caused by the female
Western Flower
Thrips (Frankliniella
occidintalis) (WFT)
inserting an egg into
the fruit when the fruit
is very small. Many
times the bloom has
not yet shed the corolla
when the injury occurs.
The number of dimples
can vary from a few to
very many. Numerous
dimples can result in the
fruit being reduced in
grade. Damage is mostly
on the surface and does
not go very deep into the
fruit. Dimple does persist
throughout the life of the fruit but halo area
may go away when fruit ripens. Control is
through management of WFT.
Zebra Stripe
Zebra stripe can be characterized as a
series of dark green spots arranged in a line
from the stem end to the bloom end. At
times, it seems the spots coalesce together
and form elongated markings. Many times
the dark green areas will disappear when
fruit ripens. This problem seems to be variety
related. It is probably a genetic defect that
only shows up under certain environmental
conditions. Zebra stripe may be linked to pox
and fleck.
Zippering
Zippering is described as a fruit
having thin scars that extend partially
or fully from the stem scar area to the
blossom end. The longitudinal scar has
small transverse scars along it. At times
there may be open holes in the locules in
addition to the zipper scar. Cause is usually
by an anther that is attached to the newly
forming fruit causing the zipper scar. Some
people feel that a zipper is formed when
the “blooms” stick to the fruit and does
not shed properly but this may not be a
cause. Only control is to select varieties
that are not prone to zippering.
Editor’s note: Stephen M. Olson is a professor
of horticultural sciences at the North Florida
Research and Education Center, Quincy, Fla. He
can be contacted by phone at (850) 875-7144 or
by e-mail at smolson@ufl .edu. Photos courtesy
of Dr. Olson.
© 2007 Columbia
Publishing
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