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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
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.

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.

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 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 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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