Physiological disorders Physiological or abiotic disorders are distinguished

Physiological disorders • Physiological or abiotic disorders are distinguished from other disorders in that they are not caused by living organisms (viruses, bacteria, fungi insects etc) • but are caused by non-living, abiotic situations and cause a deviation from normal growth. • Most of them are not reversible once they have occurred.

Physiological Tomato Fruit Disorders Blossom-end rot Dimpling Puffiness Gold Fleck Rain check Pox Zippering Catfacing Growth Cracking Graywall Internal white tissue Puffiness Zebra Stripe Sunscald Blotchy or uneven ripening

Blossom-end rot • Blossom-end rot (BER) is caused by a localized Ca deficiency in the developing fruit. It begins with light tan, water-soaked areas that can then enlarge and turn black and leathery in appearance. • It may also occur internally with no visible symptoms on outside of fruit. • 1. 2. 3. 4. 5. 6. Factors can influence BER. low soil Ca high N rates high concentrations of soluble K and Mg in the soil high salinity inadequate soil moisture or excess soil moisture damage to root system by nematodes

Blossom-end rot • 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 can not be translocated to the fruit. • Prevent with proper fertilization and good water management.

Catfacing results in fruit with deep indentations in the blossom end or fruit with significant distortions. Factors can influence Catfacing. 1. Temperatures below 10 o. C that occur 1 -2 weeks prior to flowering and fruit set that result in poor pollination. 2. Jointless varieties are more prone to catfacing than jointed varieties. 3. Heavy pruning in indeterminate varieties, because of reductions in auxins in the plant. 4. Drifts of herbicides such as 2, 4 -D can cause fruit to catface

Catfacing • Varieties should be selected that historically have had little problem with catfacing. • Try to prevent spray drift from undesirable chemicals and in the case of little leaf • Prevent soils from becoming waterlogged.

Growth Cracking Two different forms of cracking occur in tomato fruit: 1. 2. 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. Factors can influence Growth Cracking. 1. Cracking occurs when the internal expansion is faster than the expansion of the epidermis and the epidermis splits. 2. Cracking can occur at all stages of fruit growth 3. Wide fluctuation in air temperature

Growth Cracking • Cracking may be reduced by maintaining good foliage cover • Selecting tolerant varieties • Reducing fluctuations in soil moisture.

Graywall • 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 • It typically develops on green fruit prior to harvest but can develop later. • Fruits affected are typically not marketable due to blotchy appearance as fruit ripens.

Graywall • Cause is not completely understood. • Graywall is more of a problem during cool and short days. • High N may increase the problem and adequate K may reduce the problem.

Internal white tissue is a disorder where the affected fruit rarely shows any external symptoms. However, when ripe fruits are cut, white hard areas are present in the outer walls. Factors: High temperatures during the ripening period seem to trigger the symptoms. Reducing symptoms: Maintaining a sufficient potassium fertilization program (soil exchangeable potassium (K+) level of 130 PPM in sandy loams)

Dimpling • Dimpling is characterized most commonly by a small depression or dimple in the fruit. • The injury is usually caused by female thrips inserting an egg into the fruit just below the cuticle with their ovipositor when the fruit is very small. • Sometimes dimples are caused by small Lepidopteran larvae that feed briefly (one or two bites) on very small fruit or by tarnished plant bug feeding.

Dimpling • Thrips secrete a toxic substance from their salivary glands which kills the cells surrounding the feeding sites. • As the fruit enlarges, healthy tissue will expand while the dead tissue does not, which results in distorted and malformed fruit.

Gold Fleck • Fleck develops as small irregular green spots found randomly on the surface of green fruit which become yellow (gold) as the fruit ripens. • Some tomato workers believe fleck is caused by thrips or other sucking insect feeding, while others believe its cause is genetic or environmental. • There is evidence from NC that insecticide use can greatly reduce flecking, however other work has shown fleck appearing when no thrips or sucking insect was present.

Gold Fleck

Pox • Pox appears as small brown crusty disruptions found on the fruit surface that varies in number from a few to many. • Pox usually shows up on the same fruit as gold fleck but its association with thrips or sucking insect feeding has yet to be determined. • Pox is difficult to work with because it manifests itself only under certain environmental conditions.

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 • Many times the dark green areas will disappear when fruit ripens. Causes: 1. This problem seems to be variety related. 2. A genetic defect that only develops under certain environmental conditions. 3. May be linked to pox and fleck.

Sunscald appears as yellow, sunken, wrinkled, areas usually on the shoulder of the fruit. Causes: 1. Temperature rises above 300 C causes yellow pigments to develop, but not red pigments. 2. When tissue temperatures rises above 400 C the tissue turns a bleached white and dies. 3. Damage takes place when leaves are moved about or when there is foliage loss suddenly exposing the fruit to sunlight for a period of time

Sunscald • Some growers use a sun screen material such as ‘Surround’ to help reduce sunscald.

Puffiness • Puffiness causes fruit to appear somewhat bloated and flatsided or angular. • When fruit are cut, cavities may be present that lack the normal seed gel. • Fruit is less dense and feels very light in relation to its size.

Puffiness Causes: 1. Puffiness is caused by incomplete pollination and seed development and inadequate fertilization. 2. Poor pollination can occur at temperatures that are too low or too high during fruit set. 3. low light or rainy conditions can also cause seed set problems.

Rain check • Rain check appears on tomato fruit as numerous tiny concentric cracks that develop on the shoulder of the fruit. • Cracks feel rough to the touch and affected areas can take on a leathery appearance. • Green fruits are most susceptible.

Rain check Causes: Exact cause is not known. Damage occurs on exposed fruit when a heavy rain occurs after a long dry period. • There are differences among varieties to susceptibility • Good canopy coverage is necessary to avoid rain check.

Zippering • Zippering fruit have lines along the side of the fruit usually from the stem end to the blossom end due to abnormalities in early flower development. • At times a “hole” forms on the side of the fruit along the zipper. Causes: 1. The main cause is still unknown. 2. High humidity or an anther that is attached to the newly forming fruit.

Zippering • The only control is to select varieties that are not prone to zippering.

Blotchy or uneven ripening • Blotchy or uneven ripening/yellow shoulders of tomatoes is characterized by areas of the fruit that fail to ripen or do so after the rest of the fruit is ripe. • White or yellow blotches can also appear on the surface of ripening fruit while the tissue inside remains hard. • The affected area is usually on the upper portion of the fruit.

Blotchy or uneven ripening Causes: 1. More prevalent in cool, wet, often cloudy conditions. 2. Exacerbated by too much or too little water. 3. Soils high in nitrogen and/or low in potassium will increase its severity. 4. Appears more frequently on older cultivars.

Blotchy or uneven ripening Treatments: 1. Studies at UC-Davis demonstrate that for uniform color development more available potassium than is necessary for yield is needed. 2. The incidence of yellow shoulder was lower in fields with a high potassium status of both soil and plant. 3. Foliar applications of potassium, however, were not effective in relieving this disorder. 4. Soils containing greater than 3. 5% organic matter 5. Best soil p. H is between (6. 4 -6. 7)