There are some disorders in vegetable crops where there is no pathogen involved and they are more or less due to the unfavourable environmental conditions like nutrition, water, light, soil etc.
1. Fruit Splitting or Skin Cracking- The cracking around the shoulder of fruits is often associated with fluctuations in temperature and humidity.
2. Blossom end rot -Lesions appear at blossom end of the fruit while it is green. Water soaked spots appear at the point of attachment of the senescent petals. This occurs due to sudden change in the rate of transpiration, especially in reduced moisture. It can be controlled by supply light irrigation regularly, avoid heavy application of nitrgen fertilizers and adding lime to the soil or spray anhydrous calcium chloride.
3. Flower and Fruit Drop (Unfruitfulness) - Due to high temperature and low humidity, low light intensity, short day and high temperature. Give light and frequent irrigation at flowering and fruit set stages. Spray the crop either NAA 50 ppm or Tricontanol 2 ppm at full bloom stage.
4. Misshapen Fruits- This result due to non fertilization of ovule and also due to temperature difference.
5. Sun Scald- Exposed fruits shows blistered water soaked appearance. Rapid desiccation lead to sunken area usually had white or grey colour in green fruits. It can be controlled by transplanting seedling at closer spacing and grow abundant foliage varieties and control defoliating insects
6. Others like- Herbicidal injury, White Spots, Zippering
1. Bitterness- All cucurbits produce a group of chemicals called cucurbitacins, which cause the vegetables to taste bitter, and the higher the concentration of cucurbitacin the more bitter the vegetable will taste. Mild bitterness is fairly common in cucumbers resulting from higher levels of cucurbitacin triggered by environmental stress, like high temperatures, wide temperature swings or too little water. Uneven watering practices (too wet followed by too dry), low soil fertility and low soil pH are also possible stress factors. Over mature or improperly stored cucurbits may also develop a mild bitterness, which is often not severe enough to prevent gardeners from eating them.
2. Blossom-End Rot-Calcium deficiency, moisture imbalance. Symtoms and control measures same as chilli.
3. Brown End, Crooked Fruits or Crooking or Curvature or Misshapen Fruit or Pollination Problems or Low Fruit Set - Signs of incomplete pollination in cucurbits include bottlenecked fruit or fruit with a pinched end, crooked or lopsided fruit, fruit small in size or nub-like; and fruits with prominent lobes or that are triangular in shape. Causes of incomplete pollination may be inadequate pollen transfer by pollinating insects; inadequate pollen sources (pollenizers); or hot, dry weather that reduces pollen viability or that desiccates flower parts during pollination. Hollow cavities in fruit and vacant seed cavities are related to lack of seed formation, again traced back to poor pollination. Fruit tissue separation, such as hollow heart in watermelon, may also be due to inadequate pollination and may be worsened by rapid fluctuation in environmental conditions affecting fruit development.
4. Frost or Low Temperature Injury- Air temperatures at or slightly below freezing (depending on the extent of radiational cooling) can severely damage all cucurbits. Seedling stages may be severely stunted or killed by low, but non freezing temperatures because they are "chilling sensitive" crops. Damage progresses from a water-soaked appearance of affected leaf tissue immediately after exposure, to a grayish-green "scorched" appearance of leaves that eventually turn brown and papery within a day or two. Overhead irrigation applied during the low temperature exposure may provide partial protection against a light frost
5. Fruit Splitting or Cracking- Cracks, scarring and pitting can be caused by mechanical damage when fruits are young. Insects can also cause such injury. Animals, such as wild hogs and raccoons, can cause more substantial damage.
6. Hollow Heart- Hollow cavities in fruit and vacant seed cavities are related to lack of seed formation, again traced back to poor pollination. Fruit tissue separation, such as hollow heart in watermelon, may also be due to inadequate pollination and may be worsened by rapid fluctuation in environmental conditions affecting fruit development.
7. Leaf Silvering - Leaf silvering is an important physiological disorder of summer squash (Cucurbita pepo) . The symptom, in mild cases, is a silvering parallel to the veins in the upper surface of leaves, but in severe cases silvering includes the entire upper leaf surface and the bleaching of stems, petioles, flowers and fruits. Leaf silvering was distinguished from silver mottling, a genetically controlled characteristic, by differences in distribution of silver over the leaf surface, the developmental reversibility of silvering and the bleaching effect of severe silvering on various plant parts. Low soil moisture increased the severity of silvering.
8. Light Belly Colour, Measles- Physiological disorder due to salt toxicity
9. Sun Scald- Excessive or intense direct heat/ solar injury. The lack of foliage to protect the fruit can result in sunburn
1. Root Cracks - It is caused by uneven growing conditions, usually uneven watering, and are sometimes associated with secondary disease problems. Cracks are most common on large roots and on nematode-infested roots. Certain viruses also increase cracking.
2. Chilling. Sweet potatoes exposed to temperatures below 55 degrees may appear normal, but internally, the flesh may be spongy with dark vascular elements and latex does not flow. When chilled sweet potatoes are cooked, the central area of the root may be hard. The effects of chilling injury are cumulative with intermittent exposure to low temperatures. Keep storage temperatures above 55 degrees. In late fall, remove roots immediately after digging.
BRINJAL (EGG PLANT)
1. Blossom-End Rot- same as tomato
2. Fruit Cracking- same as tomato
3. Sun Scald or Sun Burn- same as tomato
4. Ethylene Damage- Ethylene, the simplest of the organic compounds affecting the physiological processes of plants, is a natural product of plant metabolism and is produced by all tissues of higher plants and by some microorganisms. As a plant hormone, ethylene regulates many aspects of growth, development, and senescence and is physiologically active in trace amounts (less than 0.1ppm). It also plays a major role in the abscission of plant organs. Generally, ethylene production rates increase with maturity at harvest, physical injures, disease incidence, increased temperatures up to 30°C, and water stress. On the other hand, ethylene production rates by fresh horticultural crops are reduced by storage at low temperature, and by reduced O2 (less than 8 percent) or ethylene is competitively inhibited by elevated CO2 (above 1 percent) levels around the commodity.
5. Frost or Low Temperature Injury - same as in cucurbits
6. Poor Fruit Set- same as tomato
1. Blossom Drop or Poor Fruit Set- Plants fail to set fruit. Cause: Extremes in temperature and dry conditions may result in poor pollination and cause the flowers to drop from the plant without setting fruit. Blossom drop on tomatoes occurs when night temperatures are below 55 F or above 75 F. Control: Water the plants deeply once a week during dry weather. Fruit set should increase when temperatures moderate. Hormone sprays, such as "Blossom Set", may prevent some blossom drop due to low temperatures. However, the resulting fruit are often misshapen. Hormone sprays do not prevent blossom drop due to high temperatures.
2. 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. Most often the problem occurs at the blossom end of the fruit, but on occasion can occur on the side of the fruit. It may also occur internally with no visible symptoms on outside of 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, excess soil moisture, damage to root system by nematodes, disease, mechanical means or heavy pruning. In greenhouse production not cycling the irrigation system at night can increase BER, since night is an important time of Ca uptake. 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. Prevent with proper fertilization and good water management.
3. Blotchy Ripening or Gray Wall- 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 develop later. Fruits affected are typically not marketable due to blotchy appearance as fruit ripens. Cause is not completely understood. There are variety differences in susceptibility. Graywall is more of a problem during cool and short days. High N may increase the problem and adequate K may reduce the problem.
4. 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 is 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 3 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 been shown to increase catfacing, but this has not been shown to happen in our short-stake varieties. In indeterminate varieties, catfacing 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 Tomato Little Leaf are severely catfaced . There is not much that can be done for control. 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
5. Fruit 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 fluctuations in soil moisture. Cracking may also be reduced by maintaining good foliage cover, since exposed fruit are more susceptible. Wide fluctuation in air temperature can also increase cracking. Cracking is more of a problem in a vine-ripe operations than in a mature-green operation.
6. Internal White Tissue or Yellow Shoulder or Green Shoulder- Fruit affected by this disorder usually show no outward symptoms. When ripe fruits 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 cross-wall and center of fruit. The problem is more of a concern with vine-ripe or u-pick production since fruit picked mature-green and gassed rarely show the problem. High temperatures during the ripening period in the field seem to trigger the symptoms. 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. The problem at times may be so severe that fruits are unmarketable.
7. Misshapen Fruits- Poor fruit setting and misshapen fruits in tomato is due to low temperature.
8. Physiological Leaf Roll, Pox and Flecks or Gold Flecks- Physiological leaf roll occurs when the edges of the leaves roll upward and inward .Sometimes the curling continues until the leaf margins from either side touch or overlap. Some leaves on the plant may not exhibit rolling. Leafroll does not reduce plant growth, yield, or fruit quality. It is believed to result from irregular water supply, and may be intensified following pruning. The symptoms are sometimes temporary, disappearing after a few days, but can persist throughout the growing season. 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, develops as small irregular shaped green spots at random on the surface of immature fruit, which become gold in color as fruit ripens. Number of spots can vary from few to many. Fruits severely affected with pox and fleck is not marketable. Both conditions seem to be genetic in nature, but are difficult to breed out of a variety since the disorders only show up under certain environmental conditions. There seems to be some differences of opinion as to the conditions inducing this problem. There are differences between varieties as to susceptibility to pox and fleck. Gold Fleck, or 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 researchers believe fleck is caused by thrips or other sucking insects, 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 insects were present. Certain varieties show a predisposition to developing fleck, whatever its cause. In my experience with Florida tomato production, fleck has not been associated with thrips feeding even though thrips are present in the field 8 or 9 months of the year. The most common thrips species in Florida tomato fields is Frankliniella bispinosa, Florida flower thrips. In the North F. tritici may be the most common species, found in vegetable fields. The inconsistency in associating fleck with thrips could be due to the difference in the species of thrips most commonly found in the field. One of my goals next year is to take a survey of the thrips species found in and around different vegetable fields throughout Maryland to see what thrips species are present, where they are located and what damage is associated with their presence.
9. Puffiness- When this problem is slight, it may be impossible to detect puffiness until fruit are cut. Severe puffy fruit will appear to be flat-sided or angular in nature. When fruit are cut, open cavities are observed between the seed gel area and the outer wall. Fruits are also very light in relation to size. This problem is caused by any factor that affects fruit set, including inadequate pollination, fertilization, or seed development. Most common causes in Florida are too low or high temperatures during fruit set. Use of "hot set" varieties can reduce the problem, but even these have limitations when night temperatures remain above about 75° F. Other factors such as high N, low light, or rainy conditions can also cause seed set problems.
10. Rain Checks- 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 fruits are most susceptible, followed by breakers and 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. The 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 fewer rain checks.
11. Sunscald or Solar Injury- Sunscald can be broken down into 2 types, sub lethal and lethal. Sub lethal sunscald can be described as a yellow, hard area usually on the shoulder of the fruit. This occurs when tissue temperature rises above about 86° F. The high tissue temperature will not allow the red pigment to develop nor the 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 fruits 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 the problem. Growers at times may use a sun screen material such as Snow or Surround to help reduce sunscald.
12. 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. Usually an anther that is attached to the newly forming fruit causes the zipper scar. Some people feel that a zipper is formed when the "blooms" stick to the fruit and do not shed properly but this may not be a cause. The only control is to select varieties that are not prone to zippering.
13. Herbicide Injury- This malady is caused by misapplication or drift of 2,4-D,MCPP, and other growth regulator herbicides. Tomato plants are highly sensitive to these chemicals throughout the growing season. The first symptom is downward curling of leaves and tips of growing points. Leaves often become narrow and twisted toward the tip, with prominent, light-colored veins. The symptoms are most pronounced on portions of the plant that were actively growing when the exposure occurred. In severe cases, stems and petioles become thick, stiff, and brittle with warty outgrowths. Affected plants usually recover. However, the fruit may become catfaced or develop in a plum shape, and may be hollow and seedless. To avoid herbicide injury, do not spray when wind may carry spray drift toward tomatoes or other sensitive crops. In addition, spray at low pressures, use a coarse-spray nozzle, and apply the spray as close to the ground as possible. Avoid applying other pesticides in sprayers that have previously contained herbicide because traces of herbicide are likely to remain in the sprayer even after thorough rinsing.
14. 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 develops under certain environmental conditions. Zebra stripe may be linked to pox and fleck.
Pods are susceptible to chilling injury, yellowing; shrivel from weight loss, warty pods (nitrogen deficiency).
About Author / Additional Info:
I am scientist working at Indian Agricultural Research Institute, New Delhi. I am working in the field of agriculture.