Tomato

Lycopersicum esculentum

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Description

Tomato, Lycopersicum esculentum (syn. Solanum lycopersicum and Lycopersicon lycopersicum) is an herbaceous annual in the family Solanaceae grown for its edible fruit. The plant can be erect with short stems or vine-like with long, spreading stems. The stems are covered in coarse hairs and the leaves are arranged spirally. The tomato plant produces yellow flowers, which can develop into a cyme of 3–12, and usually a round fruit (berry) which is fleshy, smoothed skinned and can be red, pink, purple, brown, orange or yellow in color. The tomato plant can grow 0.7–2 m (2.3–6.6 ft) in height and as an annual, is harvested after only one growing season. Tomato may also be referred to as love apple and originates from South America.

Uses

Tomato fruit can be eaten raw or cooked and is used in many dishes. The fruit may also be processed into juice, soup, ketchup, puree, paste or powder.

Propagation


Requirements
Tomatoes grow very well in warm areas at temperatures between 21 and 24°C (69.8–75.2°F). They require a deep, loamy, well-draining soil with a pH between 5.5 and 6.8. If soil drainage is a problem then tomatoes can be planted in a raised bed. Like all fruiting plants, tomatoes require full sun for most of the day.

Tomato varieties
Determinate (“bush”) tomatoes have been purposefully bred to grow vertically and remain relatively compact. The plant will stop growing once fruit begins developing on the terminal shoot and all the fruits ripen at around the same time. In contrast, indeterminate (“vining”) tomato varieties spread laterally and will continue to grow and produce fruit until frosts begin the the Fall. Indeterminate varieties can produce fruit all season and fruits will develop and ripen at different times. Heirloom tomatoes are generally open-pollinated varieties which have been conserved over many generations due to certain desirable characteristics such as flavor. Hybrid tomatoes are the product of cross-pollination between two parents with desirable characteristics such as high yield, early maturation, improved flavor or resistance to certain diseases.

Sowing seeds
In most cases, tomato seeds should be started indoors 6–8 weeks before last Spring frost. Seeds can be direct seeded in areas with a long growing season. Seeds should be sown in flats or cell trays using a sterile seedling mix. Plant seeds to a depth of 0.6 cm (1/4 in) and water lightly. If cells are being used, plant several seeds in each cell and thin to 1 seedling after germination. Position trays in a bright South facing window or under fluorescent lighting. The optimum soil temperature for germination is 21–32°C (70–90°F). A heat mat can be used to warm the flats if required. Seedlings should emerge within 6-14 days and after the seedlings has developed the first set of true leaves then they can be moved to a larger (3-4 in) pot and moved to a cooler temperature (16–21°C/60–70°F).

Transplanting
Tomato seedlings are ready to be transplanted once they are 15–25 cm (6–10 in) in height and have 3–5 true leaves assuming all danger of frost has passed. Beginning approximately 7-10 days before transplanting, plants should be set outside to harden off (see https://www.plantvillage.com/posts/264). The transplanting site should be prepared by working in a balanced fertilizer according to the guidelines on the product label. Transplants should be spaced 76–123 cm (30–48 in) apart with a between row spacing of 123 cm (48 in). It is common practice to plant tomatoes in trenches on their side (see https://www.plantvillage.com/posts/83...) as tomato stems will sprout roots along their length when buried. Avoid over-fertilizing transplants, particularly with nitrogen, at this stage of growth as it will promote growth of foliage rather than fruits. Water plants lightly at base instead of overhead as wet foliage is more prone to diseases and the buried stem needs time to adapt and sprout roots. It is important that tomato plants receive even watering to prevent the development of blossom end rot, drip or soaker hoses work best and mulching around the plants helps to conserve soil moisture.

Stakes, Cages and Trellises
Staking, caging or trellising tomatoes supports the plants and helps to keep fruit off of the ground as well as increasing air circulation around the foliage which helps to prevent disease. The type of support system used depends on the type of tomatoes being grown. Determinate tomatoes have short or medium length vines and stop growing once fruit develops on the terminal branches. Determinates can be staked or caged but do not adapt to trellises. The position of the fruit means that little heavy pruning is required. In contrast, indeterminate tomatoes grow indefinitely and require a support system to prevent them trailing along the ground. The amount of pruning required depends on the support system being utilized - vines require only light pruning when caged, moderate pruning when staked and heavy pruning when using a trellis.

Diseases

Anthracnose Fungus Colletotrichum coccodes

Symptoms

Fruit symptoms are the most common although stem, leaves and roots can also be infected; disease causes characteristic sunken circular lesions on the fruit; the indentations on may have visible concentric brown and yellow rings; lesion centers turn tan in color as they mature and become dotted with small black fungal fruiting bodies (microsclerotia); lesions can grow very large

Comments

Disease emergence favors warm weather; appears early in the spring

Management

Avoid sprinkler irrigation when fruit is ripening; rotate crops with other non-solanaceous plants

Aphids (Peach aphid, Potato aphid) Insect Myzus persicae
Macrosiphon euphorbiae

Symptoms

Small soft bodied insects on underside of leaves and/or stems of plant; usually green or yellow in color, but may be pink, brown, red or black depending on species and host plant; if aphid infestation is heavy it may cause leaves to yellow and/or be distorted, necrotic spots on leaves and/or stunted shoots; aphids secrete a sticky, sugary substance called honeydew which encourages the growth of sooty mold on the plants.

Comments

Distinguishing features of aphids include the presence of cornicles (tubular structures) which project backwards from the insect's body; aphids will generally not move very quickly when disturbed; aphids may also transmit plant viruses to the plant when they feed.

Management

If aphid population is limited to just a few leaves or shoots then the infestation can be pruned out to provide control; check transplants for aphids before planting; use tolerant varieties if available; reflective mulches such as silver colored plastic can deter aphids from feeding on plants; sturdy plants can be sprayed with a strong jet of water to knock aphids from leaves; insecticides are generally only required to treat aphids if the infestation is very high - plants generally tolerate low and medium level infestation; insecticidal soaps or oils such as neem or canola oil are usually the best method of control; always check the labels of the products for specific usage guidelines prior to use.

Bacterial canker Bacterium Clavibacter michiganensis

Symptoms

Bacterial canker can affect tomato plants of any age, seedlings may be killed quickly once they become infected; initial symptoms of bacterial canker is the unilateral wilting of plants and formation of light colored streaks up and down the outside of the leaf midrib, petiole and stem; streaks on stems may break open to form cankers; mature leaves develop small necrotic spots on the upper leaf surfaces or small raised white spots on the leaves; white spots develop on fruit, usually while they are still green; spots on fruit develop a raised dark center and are known as "bird's eye spots"

Comments

Can cause serious crop losses

Management

Plant only certified seed and transplants; hot water treatment of seed to remove bacteria; rotate crops with non-host plants; turn crops into soil after harvest to promote decomposition

Bacterial speck Bacterium Pseudomonas syringae

Symptoms

Dark specks appear on the leaves, often associated with a yellow halo; foliar symptoms of bacterial speck are very difficult to distinguish from bacterial spot but can be differentiated by symptoms on the fruit; lesions on fruit are much smaller than those caused by bacterial spot; lesions on fruit are raised and scaly.

Comments

Disease emergence favors cool, moist weather.

Management

Do not plant in same area in successive years; use only high quality, disease-free seed and transplants; protective sprays of copper can help to reduce incidence of the disease.

Bacterial spot Bacterium Xanthomonas campestris pv. vesicatoria
Xanthomonas euvesicatoria
Xanthomonas perforans = [Xanthomonas axonopodis (syn. campestris) pv. vesicatoria], Xanthomonas vesicatoria
Xanthomonas gardneri

Symptoms

Bacterial spot lesions starts out as small water-soaked spots; lesions become more numerous and coalesce to form necrotic areas on the leaves giving them a blighted appearance; of leaves drop from the plant severe defoliation can occur leaving the fruit susceptible to sunscald; mature spots have a greasy appearance and may appear transparent when held up to light; centers of lesions dry up and fall out of the leaf; blighted leaves often remain attached to the plant and give it a blighted appearance; fruit infections start as a slightly raised blister; lesions may have a faint halo which eventually disappears; lesions on fruit may have a raised margin and sunken center which gives the fruit a scabby appearance.

Comments

Bacteria survive on crop debris; disease emergence favored by warm temperatures and wet weather; symptoms are very similar to other tomato diseases but only bacterial spot will cause a cut leaf to ooze bacterial exudate; the disease is spread by infected seed, wind-driven rain, diseased transplants, or infested soil; bacteria enter the plant through any natural openings on the leaves or any openings caused by injury to the leaves.

Management

Use only certified seed and healthy transplants; remove all crop debris from planting area; do not use sprinkler irrigation, instead water from base of plant; rotate crops.

Bacterial wilt Bacterium Ralstonia solanacearum

Symptoms

Initial symptoms of the disease is the wilting of a few of the youngest leaves; the disease progresses rapidly in hot weather and the entire plant wilts suddenly and dies; in cooler conditions, wilting is less rapid and plant may produce roots on the stems; vascular tissue shows a brown discoloration and decaying roots; stems cut under water will ooze bacterial exudate and will confirm the symptoms are not caused by Fusarium wilt.

Comments

Bacterial wilt can cause complete destruction of the crop under conditions suitable for the spread of the soil-borne bacterium; disease causes serious losses in tomatoes grown in tropical and subtropical regions.

Management

Cultural practices may help to reduce incidence of the disease, rotate tomato with other, non-susceptible crops; avoid over-watering plants.

Beet armyworm Insect Spodoptera exigua

Symptoms

Singular, or closely grouped circular to irregularly shaped holes in foliage; heavy feeding by young larvae leads to skeletonized leaves; shallow, dry wounds on fruit; egg clusters of 50-150 eggs may be present on the leaves; egg clusters are covered in a whitish scale which gives the cluster a cottony or fuzzy appearance; young larvae are pale green to yellow in color while older larvae are generally darker green with a dark and light line running along the side of their body and a pink or yellow underside.

Comments

Insect can go through 3-5 generations a year.

Management

Organic methods of controlling the beet armyworm include biological control by natural enemies which parasitize the larvae and the application of Bacillus thuringiensis; there are chemicals available for commercial control but many that are available for the home garden do not provide adequate control of the larvae.

Black mold Fungus Alternaria alternata

Symptoms

Disease causes the appearance of black or brown lesions on the surface of ripe fruit; lesions may be tiny flecks or may be large patches of decaying tissue; during periods of humid weather, the lesions may become covered in black, velvety spore masses.

Comments

Disease is found wherever tomatoes are grown; ripe fruit become increasingly susceptible to the fungus the longer they stay on the vine after ripening.

Management

Cultural control methods such as avoiding wetting the foliage when watering and harvesting fruits as soon as they are ripe can help to reduce the incidence of the disease; in areas where disease is a persistent problem, chemical control may be necessary with an appropriate fungicide; fungicide is usually applied 4-6 weeks prior to the first anticipated fruit harvest.

Blossom-end rot Physiological disorder.

Symptoms

Blossom end-rot is caused by a low concentration of calcium in the tomato fruit; symptoms initially appear as light tan, water-soaked areas which can then enlarge and turn black and leathery in appearance; symptoms are most often seen at the blossom end of the fruit, but may also occur on the side of the fruit; blossom-end rot may also occur internally with no visible symptoms on outside of fruit.

Comments

Low calcium may result from competition from other ions in soil e.g. potassium; can also be caused by drought stress; fluctuations in soil moisture or application of excessive amounts of nitrogen fertilizer which promotes rapid vegetative growth; calcium cannot be translocated from the leaves to the fruit; foliar applications of Ca materials have not proven to reduce BER, since very little Ca is taken up by the fruit; in greenhouse production not cycling the irrigation system at night can increase BER, since night is an important period of Ca uptake.

Management

Maintain soil pH at 6.5; lime soil to increase the concentration of calcium in soil and decrease competition with other ions; use mulch to reduce drought stress; avoid ammonium fertilizers as they may increase competition with calcium by increasing ammonium ions in soil, use nitrate instead; avoid over fertilizing.

Buckeye rot (Phytophthora root rot) Fungi Phytophthora spp.

Symptoms

Buck eye rot of tomato initially appears as a brown spot on the fruit which enlarges over the fruit surface and forms concentric rings; the lesions may eventually cover up to half of the fruit and the flesh develops a soft rot underneath the skin; green or red fruits can be affected and disease often develops where fruit is in contact with the soil; white cottony growth may be visible in the centers of affected regions; spots enlarge and form large concentric ring shaped symptoms which are usually brown in color with sunken edges; the Phytophthora pathogen also causes root rot; young plants may exhibit a white cottony growth at crown of the plant and begin to wilt as the damage to the roots progresses; Phytophthora root rot can cause severe destruction of plant roots and cause the plants to wilt completely.

Comments

Prolonged period of warm wet conditions favor disease occurrence; heavy soil saturation also favors disease development in soils where pathogen is present; disease can be spread by splashing water.

Management

Cultural control methods such as mulching around the plants and practicing rotation away from tomato can help to reduce losses from the disease; fungicides applied for the control of late blight also help to control the development of buckeye rot; solarizing or fumigating soil can help to reduce levels of inoculum.

Catface Physiological disorder

Symptoms

Catface usually occurs on the blossom end, tomato fruits are usually misshapen with large holes or corky brown scars close to the blossom end of the fruit; fruits are often flattened and may be kidney shaped; holes on the fruit extend deep inside the fruit.

Comments

The catface deformity is possibly caused by internal or external changes that occurs during the formation of the flower resulting in the abnormal development of the fruit; the exact cause is unknown, there may be several factors in fruit deformation; cold weather is known to be a factor along with extreme fluctuations in temperatures between day and night; hormone based herbicides may also cause catfacing; varieties that produce large tomatoes are more prone to catfacing.

Management

Avoid pruning tomato plants excessively; avoid excessive fertilization with nitrogen which promotes rapid vegetative growth; if growing tomatoes in a glasshouse, provide the plants with heat to prevent temperatures dropping to damaging levels, particularly at night.

Colorado potato beetle Insect Leptinotarsa decemlineata

Symptoms

Feeding damage to foliage; if infestation is severe or if left untreated plants can be completely defoliated; adult insect is a black and yellow striped beetle; larvae are bright red with black heads when they first hatch and change color to pink; larvae have two rows of black spots.

Comments

Adult beetles emerge in spring; female beetles lay eggs in batches of up to two dozen; eggs are orange-yellow and are laid on undersides of leaves; a female can lay 500 or more eggs over a four to five week period.

Management

Control of Colorado potato beetle can be challenging as they have developed high levels of insecticide resistance; adults and larvae should be hand picked from plants and destroyed in soapy water; applications of Bacillus thuringiensis can be effective at controlling larvae but should be applied frequently; some insecticides, including spinosad, are still effective against adult beetles.

Curly top Virus Beet curly top virus (BCTV)

Symptoms

Young plants are usually killed by the virus; older plants are stunted and turn yellow to bronze in color with purple-tinged leaves; leave become thickened and roll upwards; leaf petioles roll downwards; green fruit turns red regardless of its age and becomes dull in color and wrinkled; plants do not recover form the disease and will not flower of produce fruit after infection.

Comments

Virus is transmitted by beet leafhoppers; insects transmit the disease between over 300 species of plant, including beets, tomato, squash, swiss chard, cucumber and melon.

Management

There is no resistance to Beet curly top virus in tomato so control relies on the management of the leafhopper vector; dense stands of tomato may discourage leafhoppers from visiting the plants; chemical spraying programs to protect against beet leafhoppers have been implemented in some areas of the US state of California ; in areas where the virus is a chronic problem, n areas where curly top is chronic, dense plant spacing, shading, row covers, and intercropping have been reported to reduce levels of infection.

Cutworms Insect Various species including:
Agrotis spp.
Peridroma saucia
Nephelodes minians
etc.

Symptoms

Stems of young transplants or seedlings may be severed at soil line; if infection occurs later, irregular holes are eaten into the surface of fruits; larvae causing the damage are usually active at night and hide during the day in the soil at the base of the plants or in plant debris of toppled plant; larvae are 2.5–5.0 cm (1–2 in) in length; larvae may exhibit a variety of patterns and coloration but are usually dirty gray or brown to black with dark spots or lines and will curl up into a characteristic C-shape when disturbed

Comments

Cutworms have a wide host range and attack vegetables including asparagus, bean, cabbage and other crucifers, carrot, celery, corn, lettuce, pea, pepper, potato and tomato

Management

Remove all plant residue from soil after harvest or at least two weeks before planting, this is especially important if the previous crop was another host such as alfalfa, beans or a leguminous cover crop; plastic or foil collars fitted around plant stems to cover the bottom 3 inches above the soil line and extending a couple of inches into the soil can prevent larvae severing plants; hand-pick larvae after dark; spread diatomaceous earth around the base of the plants (this creates a sharp barrier that will cut the insects if they try and crawl over it); apply appropriate insecticides to infested areas of garden or field if not growing organically

Early blight Fungus Alternaria solani

Symptoms

Early blight symptoms start as oval shaped lesions with a yellow chlorotic region across the lesion; concentric leaf lesions may be seen on infected leaves; leaf tissue between veins is destroyed; severe infections can cause leaves to completely collapse; as the disease progresses leaves become severely blighted leading to reduced yield; tomato stems may become infected with the fungus leading to Alternaria stem canker; initial symptoms of of stem canker are the development of dark brown regions on the stem; stem cankers may enlarge to girdle the whole stem resulting in the death of the whole plant; brown streaks can be found in the vascular tissue above and below the canker region; fruit symptoms include small black v-shaped lesions at the shoulders of the fruit (the disease is also known black shoulder); lesions may also appear on the fruit as dark flecks with concentric ring pattern; fruit lesions can seen in the field or may develop during fruit transit to the market; the lesions may have a velvety appearance caused by sporulation of the fungus

Comments

Disease can spread rapidly after plants have set fruit; movement of air-borne spores and contact with infested soil are causes for the spread of the disease

Management

Apply appropriate fungicide at first sign of disease; destroy any volunteer solanaceous plants (tomato, potato, nightshade etc); practice crop rotation

Edema (Oedema) Physiological disorder

Symptoms

Swellings and/or blisters or calluses on leaves caused by rupturing epidermal and inner leaf cells ; deformed foliage which curls; leaf tissue may also tear as the leaf matures; symptoms are often mistaken for disease or insect damage

Comments

Edema occurs when water is absorbed from the soil faster than it can be transpired through the leaves and is caused by soil being warmer than the surrounding air

Management

Tomato plants should always be planted in well draining soil or potting media; avoid overwatering tomato plants, particularly during periods of low light and cool temperatures; if growing tomatoes in a glasshouse then anything that can be done to increase drainage and air circulation will be helpful in preventing edema; reduce humidity in the glasshouse in the morning by venting the house (heat may need to be turned up during this period depending on outdoor temperatures)

Fertilizer burn Excess nitrogen salts

Symptoms

Symptoms may first appear as slowed growth and wilting; leaf tips and margins turn brown; plants have a scorched appearance.

Comments

Fertilizer burn is usually caused by an excess of nitrogen salts in the soil which causes an osmotic stress on the plant tissues. The tissues dry out and die resulting in the characteristic scorched appearance of the leaves.

Management

Apply appropriate dose of fertilizer for the particular soil in which the plants are growing - nutrient requirements can be ascertained with a soil test; if liquid fertilizer was used, symptoms may be reversed by watering the plants heavily to leach some of the salts from the soil.

Flea beetles Insects Epitrix spp.

Symptoms

Small holes or pits in leaves that give the foliage a characteristic “shothole” appearance; young plants and seedlings are particularly susceptible; plant growth may be reduced; if damage is severe the plant may be killed; feeding damage may also occur on the fruit; the pest responsible for the damage is a small (1.5–3.0 mm) dark colored beetle which jumps when disturbed; the beetles are often shiny in appearance.

Comments

Flea beetles may overwinter on nearby weed species, in plant debris or in the soil; insects may go through a second or third generation in one year.

Management

In areas where flea beetles are a problem, floating row covers may have to be used prior to the emergence of the beetles to provide a physical barrier to protect young plants; plant seeds early to allow establishment before the beetles become a problem - mature plants are less susceptible to damage; trap crops may provide a measure of control - cruciferous plants are best; application of a thick layer of mulch may help prevent beetles reaching surface; application on diamotecoeus earth or oils such as neem oil are effective control methods for organic growers; application of insecticides containing carbaryl, spinosad, bifenthrin and permethrin can provide adequate control of beetles for up to a week but will need reapplied.

Fusarium wilt Fungus Fusarium oxysporum

Symptoms

Symptoms of Fusarium wilt may first appear as yellowing and wilting of leaves on one side of the leaf midrib or plant; one-sided symptoms are caused by a blockage in the vascular system supplying the symptomatic side of the plant; as the disease progresses, older leaves become necrotic and the plant begins to wilt; fruit on infected plants is smaller and yield is reduced; damage to leaves makes fruit susceptible to sunscald; stem symptoms may be mistaken for bacterial wilt but a bacterial ooze test will be negative; stem tissue becomes discolored brown

Comments

Disease emergence favors warm, moist soil Fusarium wilt is not a major issue in tomato production, however, the disease can still cause minor losses

Management

Plant resistant varieties; sanitize all equipment regularly; control root knot nematodes; rotate crops away from tomato for several years

Gray mold (Botrytis blight) Fungus Botrytis cinerea

Symptoms

Disease appears on tomato seedlings at or just below the soil line as a fuzzy gray-brown lesion which often girdles the stem, if stem is girdled all parts of the plant above the lesion begin to wilt; infected flowers and calyxes become covered in gray spores; unripe fruit turns light brown or gray in color and rots; green fruit infected by airborne spores develop circular white rings called “ghost spots”.

Comments

Gray mold is usually associated with wounds on plants; can develop in relatively cool conditions.

Management

Liming soil to increase calcium content can help to reduce plant susceptibility to gray mold; application of appropriate fungicide prior to formation of dense canopy.

Hornworms (Tomato hornworm, Tobacco hornworm) Insect Manduca quinquemaculata
Manduca sexta

Symptoms

Feeding damage to leaves or leaves stripped from plant; heavy infestation may result in damage to fruit appearing as large open scars; large green caterpillars may be spotted on plant; caterpillars may reach in excess of 7.5 cm (3 in) in length and possess a spike at the end of their body; most common species have 7 diagonal stripes on sides or 8 v-shaped markings on each side; single eggs may be present on leaves and measure approx 1.3 mm in diameter; eggs are in initially light green in color and turn white prior to hatching.

Comments

Insect overwinters as pupa in soil; typically undergoes 2 generations per year; heavy infestations are more common in warm areas.

Management

Hand pick larvae from plants leaving any parasitized larvae behind to promote populations of natural enemies (these larvae can be distinguished by the presence of white, oblong-shaped cocoons on their backs); sprays of Bacillus thuringiensis are organically acceptable and highly effective.

Late blight Oomycete Phytophthora infestans

Symptoms

Late blight affects all aerial parts of the tomato plant; initial symptoms of the disease appear as water-soaked green to black areas on leaves which rapidly change to brown lesions; fluffy white fungal growth may appear on infected areas and leaf undersides during wet weather; as the disease progresses, foliage becomes becomes shriveled and brown and the entire plant may die; fruit lesions start as irregularly shaped water soaked regions and change to greasy spots; entire fruit may become infected and a white fuzzy growth may appear during wet weather.

Comments

Can devastate tomato plantings.

Management

Plant resistant varieties; if signs of disease are present or if rainy conditions are likely or if using overhead irrigation appropriate fungicides should be applied.

Leafminers Insect Tuta absoluta
Lyriomyza spp.

Symptoms

Thin, white, winding trails on leaves; heavy mining can result in white blotches on leaves and leaves dropping from the plant prematurely; early infestation can cause fruit yield to be reduced; adult leafminer is a small black and yellow moth which lays its eggs in the leaf; larvae hatch and feed on leaf interior.

Comments

Origin and distribution of Tuta absoluta: This species is originated in South American countries. Later the insect spread to Spain (2006), France, Italy, Greece, Malta, Morocco, Algeria, Libya and Turkey in following years. Further the insect has been identified in Syria, Lebanon, Jordan, Iraq, Iran, Saudi Arabia, Yemen, Oman and the rest of the Gulf states. In Africa it spreads from Egypt to Sudan, South Sudan, Ethiopia, Uganda, Kenya and Tanzania (in East) and to Senegal and Nigeria through the west. (It spread through infested fruits and packaging materials)

Life cycle: Mature larvae drop from leaves into soil to pupate; entire lifecycle can take as little as 2 weeks in warm weather; insect may go through 7 to 12 generations per year.

Yield loss: If unchecked, insect will cause 100% yield loss. The larvae feeds on apical buds, tender new leaflets, flowers, and green fruits which make it a serious pest in tomato.

Host Range: This insect also attacks other solanaceous crops like potato, eggplant, pepino and tobacco. It is also reported on many solanaceous weeds.

Management

Leafminer natural enemies normally keep populations under control; check transplants for signs of leafminer damage prior to planting; remove plants from soil immediately after harvest if making new plantings in same place or close by; keep the field free from weeds especially Solanum, Datura, Nicotiana; use pheromone traps and white sticky traps to monitor and control insect;only use insecticides when leafminer damage has been identified as unnecessary spraying will also reduce populations of their natural enemies.

Leaf Mold Fungus Passalora fulva

Symptoms

The older leaves exhibit pale greenish to yellow spots (without distinguishable margins) on upper surface. Whereas the lower portion of this spots exhibit green to brown velvety fungal growth. As the disease progress the spots may coalesce and appear brown. The infected leaves become wither and die but stay attached to the plant. The fungus also infects flowers and fruits. The affected flowers become black and drop off. The affected fruit intially shows smooth black irregular area on the stem end but later it becomes sunken, leathery and dry.

Comments

The disease is favored by high relative humidity. Also a common disease in green house tomato crop.

Management

Grow available resistant varieties. Avoid leaf wetting and overhead application of water. Follow proper spacing to provide good air circulation around the plants. Remove the infected plant debris and burn them. If the disease is severe scary suitable fungicide.

Little leaf Physiological disorder

Symptoms

Little leaf symptoms include interveinal chlorosis of young leaves, distortion and failure of leaves along the midrib to expand, radial cracks of fruits extending from the calyx to the blossom scar and failure of blooms to set; symptoms progress to increased leaflet distortion and more pronounced interveinal chlorosis.

Comments

Three conditions appear to pre-dispose plants to little leaf. 1) high soil temperatures 2) high soil moisture and 3) presence of predisposing population of bacterial/fungal microorganisms in the soil.

Management

Little leaf is usually associated with water-logged areas of fields, subsequent drying out of affected areas usually resolves the problem and subsequent plant growth is normal; controlling the soil pH may also help the problem.

Loopers (Cabbage looper , Alfalfa looper) Insect Trichoplusia ni
Autographa californica

Symptoms

Large or small holes in leaves; damage often extensive; caterpillars are pale green with a white lines running down either side of their body; caterpillars are easily distinguished by the way they arch their body when moving; eggs are laid singly, usually on the lower leaf surface close to the leaf margin, and are white or pale green in color.

Comments

Insects overwinter as pupae in crop debris in soil; adult insect id a dark colored moth; caterpillars have a wide host range.

Management

Looper populations are usually held in check by natural enemies; if they do become problematic larvae can be hand picked from the plants; an organically acceptable control method is the application of Bacillus thuringiensis which effectively kills younger larvae; chemical sprays may also damage populations of natural enemies and should only be considered if sunburn of fruit is likely.

Magnesium deficiency Nutritional disorder

Symptoms

Symptoms of magnesium deficiency appear on older leaves first; initial symptoms are interveinal chlorosis of the leaves and, occasionally, a purple tinge to the leaves; as the deficiency becomes more severe, leaves may appear white with green veins; severe deficiencies may lead to reduced fruit yield.

Comments

Magnesium deficiency is rare in field grown tomatoes but occurs more frequently in soilless tomato culture.

Management

Magnesium deficiency can be prevented in tomato by applying dolomite lime to the soil, if an increase in soil pH is required, or through applications of a fertilizer containing magnesium.

Multiple nutrients deficiency Nutritional disorder

Nitrogen deficiency Nutritional disorder

Symptoms

Affected plants are smaller in size and grow less vigorously than healthy plants; symptoms appear on older leaves first; tomato leaves exhibit a general yellowing occasionally accompanied by purple leaf veins; plants possess thinner stems and fruit is smaller than healthy plants; fruits may be misshapen with a lighter red color than healthy plants.

Comments

Nitrogen deficiency usually arises in tomato plantations through inadequate fertilizer application; heavy rain can leach nitrogen from sandy soils.

Management

If detected early, symptoms of nitrogen deficiency can be treated by applying appropriate amounts of nitrogen fertilizer.

Phosphorous deficiency Nutritional disorder

Symptoms

Growth of tomato seedlings is reduced compared with healthy plants; leaves appear darker green and may have a purple tinge; in older tomato plants, leaves grow upright and appear light green on the upper surface and purple on the lower surface; symptoms appear on older leaves first.

Comments

Phosphorous deficiency is rare in soils that are already used for agricultural purposes; in field grown tomatoes phosphorous deficiency more commonly appears in newly cleared land which has never been used to grow crops; phosphorus deficiency may occur on soilless tomato cultures if applications of the nutrient are inadequate.

Management

Soil levels of phosphorous should be measured prior to planting to determine the appropriate application for the particular site; phosphorous should be applied to the soil prior to planting if required as applications made after the onset of tomato growth are not usually successful in preventing symptoms.

Potassium deficiency Nutritional disorder

Symptoms

Affected plants are smaller than healhty plants with smaller fruits and reduced yields; tomato leaves exhibit "bronzing", older plant leaves turn tan and then brown at the margins; if deficiency is prolonged, leaves become necrotic at the margins and turn yellow between leaf veins.

Comments

Potassium deficiency is usually caused by an inadequate fertilization, it is more common in sandy soils where the nutrient is easily leached from the soil by heavy rainfall.

Management

Potassium deficiency can be corrected through applications of the nutrient as a side dressing and/or through an irrigation system.

Root knot nematode Nematode Meloidogyne spp.

Symptoms

The characteristic symptom of root knot nematodes is the presence of galls on roots which can be up to 3.3 cm (1 in) in diameter but are usually smaller; galls cause a reduction in plant vigor; if the galls on the roots are extensive then plants may yellow and wilt, particularly in hot weather.

Comments

Galls can appear as quickly as a month prior to planting; nematodes prefer sandy soils and damage in areas of field or garden with this type of soil is most likely; disease can be a major problem if soils are infected with Meloidogyne sp. and resistant varieties are not used for production.

Management

Plant resistant varieties if nematodes are known to be present in the soil ;check roots of plants mid-season or sooner if symptoms indicate nematodes; solarizing soil can reduce nematode populations in the soil and levels of inoculum of many other pathogens.

Septoria leaf spot Fungus Septoria lycopersici

Symptoms

Symptoms may occur at any stage of tomato development and begin as small, water-soaked spots or circular grayish-white spots on the underside of older leaves; spots have a grayish center and a dark margin and they may colasece; fungal fruiting bodies are visible as tiny black specks in the center of spot; spots may also appear on stems, fruit calyxes, and flowers.

Comments

Spread by water splash; fungus overwinters in plant debris.

Management

Ensure all tomato crop debris is removed and destroyed in Fall or plowed deep into soil; plant only disease-free material; avoid overhead irrigation; stake plants to increase air circulation through the foliage; apply appropriate fungicide if necessary.

Spider mites (Two-spotted spider mite) Arachnid Tetranychus urticae

Symptoms

Leaves stippled with yellow; leaves may appear bronzed; webbing covering leaves; mites may be visible as tiny moving dots on the webs or underside of leaves, best viewed using a hand lens; usually not spotted until there are visible symptoms on the plant; leaves turn yellow and may drop from plant.

Comments

Spider mites thrive in dusty conditions; water-stressed plants are more susceptible to attack.

Management

In the home garden, spraying plants with a strong jet of water can help reduce buildup of spider mite populations; if mites become problematic apply insecticidal soap to plants; certain chemical insecticides may actually increase mite populations by killing off natural enemies and promoting mite reproduction.

Stinkbugs (Various) Insect Various

Symptoms

Dark colored pinpricks on fruit surrounded by a lighter area that turns yellow or remains light green; stink bugs often carry pathogens in their mouthparts which can cause secondary infections and decay of fruit; adult insect is shield-shaped and brown or green in color; may have pink, red or yellow markings; eggs are drum shaped and laid in clusters on the leaves; larvae resemble the adults but are smaller.

Comments

Several types of stink bug can cause damage to tomatoes; adult insects overwinter under leaves, on legumes, blackberries or on certain weeds such as mustard or Russian thistle.

Management

Remove weeds around crop which may act as overwintering sites for stink bugs and practice good weed management throughout the year; organically accepted control methods include the use of insecticidal soaps, kaolin clay and preservation of natural enemies; chemical treatments are not recommended for tomatoes that are to be processed for paste or canning unless secondary infections with other pathogens are a concern.

Sunscald Physiological disorder

Symptoms

Symptoms of sunscald are most common on green fruit; white or yellow necrotic patches develop on the sides of the fruit that are facing the sun; blisters may be white with a yellow halo; damaged areas may become flattened in appearance and papery in texture; damaged areas are often invaded by secondary pathogens and turn black.

Comments

Sunscald is common on plants which have been moved suddenly from a shaded location to full sun.

Management

Healthy plants with full foliage are less susceptible to sunscald as the leaves provide fruits with shading, ensure plants are watered regularly and fertilized adequately; use shade cloth to protect the fruits from the sun; control diseases that develop to prevent defoliation which can lead to sunscald.

Target Spot Fungus Corynespora cassiicola

Symptoms

The fungus infects all parts of plant. Infected leaves shows small, pinpoint, water soaked spots initially. As the disease progress the spots enlarge to become necrotic lesions with conspicuous concentric circles, dark margins and light brown centers. Whereas the fruits exhibit brown, slightly sunken flecks in the beginning but later the lesions become large pitted appearance.

Comments

The pathogen infects cucumber, pawpaw , ornamental plants, some weed species etc. The damaged fruits are susceptible for this disease.

Management

Remove the plant debris and burn them. Avoid over application of nitrogen fertilizer. If the disease is severe spray suitable fungicides.

Thrips (Western flower thrips, Onion thrips, etc.) Insect Frankliniella occidentalis
Thrips tabaci

Symptoms

If population is high leaves and buds may be distorted; leaves appear silvery and are speckled with black feces; most damage occurs through the transmission of Tomato spotted wilt virus (TSWV); insect is small (1.5 mm) and slender and best viewed using a hand lens; adult thrips are pale yellow to light brown and the nymphs are smaller and lighter in color.

Comments

Transmit Tomato spotted wilt virus (see disease entry); once acquired, the insect retains the ability to transmit the virus for the remainder of its life.

Management

Avoid planting next to onions, garlic or cereals where very large numbers of thrips can build up; use reflective mulches early in growing season to deter thrips; apply appropriate insecticide if thrips become problematic.

Tomato fruit worm (Corn earworm) Insect Helicoverpa zea

Symptoms

Holes in tomato fruit, including entry holes near stem end; feeding turns inside of tomato into a watery cavity filled with cast skins and frass (insect feces); damaged fruit ripens prematurely; young caterpillars are cream-white in color with a black head and black hairs; older larvae may be yellow-green to almost black in color with fine white lines along their body and black spots at the base of hairs; eggs are laid singly on both upper and lower leaf surfaces and are initially creamy white but develop a brown-red ring after 24 hours and darken prior to hatching.

Comments

Adult insect is a pale green to tan, medium sized moth; can be one of the most damaging pests of tomato; insect overwinters as pupae in the soil; the insect is also a damaging pest of corn and is also referred to as the corn earworm.

Management

Early treatment of tomato fruitworms is necessary as once they enter the fruit they are protected from sprays; monitor plants for eggs and young larvae and also natural enemies that could be damaged by chemicals; Bacillus thuringiensis or Entrust SC may be applied to control insects on organically grown plants; appropriate chemical treatment may be required for control in commercial plantations.

Tomato mosaic virus Virus Tomato mosaic virus (ToMV)

Symptoms

Symptoms can occur at any growth stage and any part of the plant can be affected; infected leaves generally exhibit a dark green mottling or mosaic; some strains of the virus can cause yellow mottling on the leaves; young leaves may be stunted or distorted; severely infected leaves may have raised green areas; fruit yields are reduced in infected plants; green fruit may have yellow blotches or necrotic spots; dark necrotic streaks may appear on the stems, petioles leaves and fruit.

Comments

ToMV is a closely related strain of Tobacco mosaic virus (TMV), it enters fields via infected weeds, peppers or potato plants; the virus may also be transmitted to tomato fields by grasshoppers, small mammals and birds.

Management

Plant varieties that are resistant to the virus; heat treating seeds at 70°C (158°F) for 4 days or at 82–85°C (179.6–185°F) for 24 hours will help to eliminate any virus particles on the surface of the seeds; soaking seed for 15 min in 100 g/l of tri-sodium phosphate solution (TSP) can also eliminate virus particles - seeds should be rinsed thoroughly and laid out to dry after this treatment; if the virus is confirmed in the field, infected plants should be removed and destroyed to limit further spread; plant tomato on a 2-year rotation, avoiding susceptible crops such as peppers, eggplant, cucurbits and tobacco; disinfect all equipment when moving from infected areas of the field.

Tomato spotted wilt Virus Tomato spotted wilt virus (TSWV)

Symptoms

Infected plants exhibit bronzing or purpling of the upper sides of young leaves and develop necrotic spots; leaf spots may resemble those caused by bacterial spot, but a bacterial ooze test will be negative; leaves may cup downwards, shoot tips may begin to die back; symptoms on ripe fruit appear as chlorotic spots and blotches, often with concentric rings; ring spot symptoms vary with different tomato cultivars; irregular ripening caused by TSWV can also show up when fruit are treated with ethylene gas; green fruit may exhibit slightly raised areas with faint concentric zonation.

Comments

TSWV infects numerous ornamentals, vegetables, field crops and weeds; virus is vectored by at least eight species of thrips; thrips, acquires the virus during the larval stages,and transmit the virus when they are adults.

Management

Control populations of western flower thrips and onion thrips

Tomato Yellow Leaf Curl disease Virus Tomato Yellow Leaf Curl Virus (TYLCV)
family Geminiviridae, genus Begomovirus

Symptoms

The infected leaves become reduced in size, curl upward, appear crumpled and show yellowing of veins and leaf margins. The internodes become shorter and whole plant appear stunted and bushy. The whole plant stand erect with only upright growth. The flowers may not develop and drop off.

Comments

The virus is transmitted by white flies and may cause 100 % yield loss if the plants infect at early stage of crop. The virus also infect other hosts like common bean, ornamental plants and several weed species.

Management

Grow available resistant varieties. Transplant only disease and whiteflies free seedlings. Remove the infected plants and burn them. Keep the field free from weeds. Use yellow sticky traps to monitor and control whiteflies. If the insect infestation is severe spray suitable insecticides.

Verticillium wilt Fungi Verticillium albo-atrum
Verticillium dahliae

Symptoms

Symptoms appear first on lower leaves and spread upwards; initial symptoms of the disease may be visible as yellow blotches on the lower leaves of the plant; a rapid yellowing of leaves follows as the disease progresses; leaf veins turn brown and brown dead spots appear on the leaves; leaves may wilt then die and drop from the plant; the disease progresses upwards through the stem causing the plant to be stunted; leaves at the top of the plant remain green; fruits develop yellow shoulders and yield is reduced; loss of leaves results in fruit being susceptible to sun scald.

Comments

Fungi survive in crop debris in soil; disease emergence favors cool weather.

Management

Plant resistant varieties; sanitize all equipment on a regular basis; rotate with non-susceptible crops.

Water stress Physiological stress

Symptoms

Leaves are green but wilting; leaves roll downwards and eventually drop from the plant; fruits may develop symptoms of Blossom-end rot (See entry).

Comments

It is important to distinguish between plants that are temporarily wilted on hot days and those that are stressed due to lack of moisture in the soil; on very hot days tomato plants will wilt as the rate of transpiration exceeds the rate at which water can be taken up from the soil by the roots and the plants will usually recover in the evening when temperatures are cooler.

Management

Tomato plants should be watered deeply and evenly to avoid water stress; aim to keep the soil moist but not wet; allow the top of the soil to dry before watering again.

Zippering Physiological disorder

Symptoms

Thin brown scars extending longutudinally from the petiole to the blossom-end of the fruit; each scar has smaller scars crossing it tranversely rendering it zipper-like in appearance; holes may open on along the scarred area.

Comments

Zipper scars on tomato fruit are most prevalent in cool weather.

Management

The most effective method of preventing zippering is to grow tolerant varieties; when growing tomatoes in the glasshouse, appropriate temperatures should be maintained.

References

AVRDC Publication 04-609 (2004). Tomato mosaic virus (ToMV). AVRDC. Available at: http://203.64.245.61/web_crops/tomato.... [Accessed 22 April 15]. Free to access.

CABI Crop Protection Compendium. (2013). Solanum lycopersicum (tomato) datasheet. Available at: http://www.cabi.org/cpc/datasheet/31837. [Accessed 09 February 14]. Paid subscription required.

Jones, J. P., Stall, R. E. & Zitter, T. A. (1991). Compendium of Tomato Diseases. American Phytopathological Society Press. Available for purchase from APS Press.

Kopsell, D. (2000). Growing tomatoes. University of New Hampshire Cooperative Extension. Available at: http://extension.unh.edu/resources/fi.... [Accessed 09 February 15]. Free to access

Lerner, B. R. Tomatoes. Purdue University Cooperative Extension. Available at: http://www.hort.purdue.edu/ext/HO-26.PDF. [Accessed 09 February 15]. Free to access

U-Scout (2014). Tomato diseases. Plant Pathology Lab, NFREC. University of Florida Cooperative Extension. Available at: http://nfrec.ifas.ufl.edu/paret/u-sco.... [Accessed 09 February 15]. Free to access