Tomato diseases

Here are described some important diseases of tomato.This PPT is small effort by me for students of agriculture and other people.

1. DISEASES OF TOMATO By Ms.Dipali R More M.Sc (Agri)

2. Bacterial canker Bacterial spot Bacterial wilt Bacterial speck Early blight Late blight

3. TOMATO CANKER ( Clavibacter michiganesis pv. michiganesis ) INTRODUCTION GRAM +Ve Non motile Non flagellate strictly aerobic bacteria. Described in 1910 as the cause of bacterial canker of tomato in North America .

4. SYMPTOMS First symptom is downward curling and wilting of lower leaves. Unilateral wilting,light colored stricks on leaves. Light brown or yellow vascular discoloration of stem. Yellow bacterial ooze. Birds eye appearance on fruits.

5. Conditions for disease development Infection occurs through wounds in plant tissue or leaf stomata or roots. Bacteria can survive in soil and infected plant debris for up to five years. It can also survives on weeds, volunteer plants and seeds. Secondary spread: Splashing water, contaminated equipments, tools used in pruning, clipping and transplanting operations.

6. Temperature :Moderate (18-24°C). RH : Greater than 80%. Opt. moisture conditions for plant growth. Low light intensity. High nutrients conc.( specially nitrogen). Sandy soil.

7. Appearance of cultures of three different Cmm isolates

8. Appearance of cultures of three different Cmm isolates after 10 days of incubation.

9. Appearance of cultures of six representative colonies of Cmm showing variation in colony morphology after 3 days of incubation

10. CELL MORPHOLOGY Cells of Cmm are Gram +Ve. N on-motile , non-spore-forming, short rods. May be straight to slightly curved or wedge shaped. Coccoid forms may also be observed . They predominantly appear as single cells, but some V, Y and palisade arrangements are usually also present. Primary branching is uncommon.

11. TREATMENTS AND CONTROL Disease free seed selection: It is not recommended that tomato growers save and use their own seed. Use of Hot Water Treatment. Treatment with 8% acetic acid or 5% hydrochloric acid. Tomato crop rotation for 3 yrs. Soil Steam Sterilization. Purchase healthy transplants from a reputable grower. Avoid transplants that have been pruned or cut back as this procedure easily spreads the bacterial pathogen. Disinfest tools and equipment between seasons with a commercial greenhouse sanitizer according to label instructions . Discard strings and wooden stakes.

12. Avoid working in fields when the foliage is wet with rain, irrigation, or dew. Use a commercial greenhouse sanitizer or a 1:9 solution of bleach to water, to regularly clean pruning tools. In greenhouse or high tunnel production, promptly bag and remove infected plants, including roots to prevent spread. Remove and/or plow in remaining plant debris immediately after harvest to encourage decomposition. Infected plant debris can be composted on site. The pathogen will be killed if the compost heats up and all plant parts are completely broken down. Rotate away from tomato and related crops for two to three years. Control weeds in the solanaceae family, like nightshades, as well as volunteer tomatoes or peppers during the rotation.

13. BACTERIAL SPOT ( Xanthomonas vesicatoria ) INTRODUCTION Is a potentially devastating disease that, in severe cases, can lead to unmarketable fruit and even plant death. Can occur wherever tomatoes are grown, but is found most frequently in warm, wet climates, as well as in greenhouses.

14. SYMPTOMS Spot appears on leaves as small, sometimes water-soaked (i.e., wet-looking) circular areas. Spots may initially be yellow-green, but darken to brownish-red as they age. On green fruit, spots are typically small, raised and blister-like, and may have a yellowish halo. As fruit mature, the spots enlarge and turn brown, scabby and rough. Mature spots may be raised, or sunken with raised edges. Bacterial spot symptoms can be easily confused with symptoms of another tomato disease called bacterial speck.

15. CONDITIONS FOR DISEASE DEVELOPMENT Can survive in plant debris, volunteer plants, weeds and seeds. Disease spread rapidly through seed beds and fields by sprinkler irrigation and wind driven rains. Infection generally occurs by wounds. Warm temp.(24-30°C) with sprinkler irrigation.

16. MANAGEMENT AND CONTROL Remove symptomatic plants from your garden or greenhouse. Burn, bury or hot compost the affected plants. Soak seeds in water at 122°F for 25 min. before sowing. To keep leaves dry and to prevent the spread of the pathogens, avoid overhead watering and instead use a drip-tape or soaker-hose. Also to prevent spread, DO NOT handle plants when they are wet and routinely sterilize tools with either 10% bleach solution or (better) 70% alcohol (e.g., rubbing alcohol). Consider using preventative applications of copper-based products registered for use on tomato, especially during warm, wet periods. Keep in mind however, that if used excessively or for prolonged periods, copper may no longer control the disease. Burn, bury or hot compost tomato debris at the end of the season Wait at least one year before planting tomatoes in a given location again.

17. BACTERIAL WILT ( Ralstonia solanacearum ) introduction The disease is caused by the bacterium Ralstonia solanacearum, previously known as Pseudomonas solanacearum . It is one of the most damaging plant pathogens. Strains of this pathogen affect more than 200 plant species in over 50 families throughout the world, including a wide range of crop plants, ornamentals and weeds.

18. SYMPTOMS At the early stages of disease, the first visible symptoms are usually seen on the foliage of plants. These symptoms consist of wilting of the youngest leaves at the ends of the branches during the hottest part of the day. At this stage, only one or half a leaflet may wilt and plants may appear to recover at night, when the temperatures are cooler. As the disease develops under favorable conditions, the entire plant may wilt quickly and desiccate although dried leaves remain green, leading to general wilting and yellowing of foliage and eventually plant death.

19. These symptoms may appear at any stage of plant growth, although in the field it is common for healthy-appearing plants to suddenly wilt when fruits are rapidly expanding. In young tomato stems, infected vascular bundles may become visible as long, narrow, dark brown streaks. In young, succulent plants of highly susceptible varieties, collapse of the stem may also be observed. In well-established infections, cross-sections of stems may reveal brown discoloration of infected tissues.

20. This “stem-streaming” test is easy to conduct and can be used as a valuable diagnostic tool for quick detection of bacterial wilt in the field.

21. Causal organism Gram-negative. Rod shaped. Strictly aerobic. 0.5-0.7 x 1.5-2.0 cm in size. Very sensitive to desiccation and is inhibited in culture by low concentrations (2%) of sodium chlorid (NaCl). The optimal growth temp. is between 28-32°C; however some strains have a lower optimal growth temperature of 27°C.

22. CONDITIONS FOR DISEASE DEVELOPMENT Can survive for days to years in infected plant material in soils, infested surface irrigation water and infected weeds. From these sources of inoculum, bacteria can spread from infested to healthy fields by soil transfer on machinery, and surface runoff water after irrigation or rainfall. High temperatures (29-35ºC) play a major role in pathogen growth and disease development. Several other factors that soil type and structure, soil moisture content, organic matter in soil, water pH and salt content and the presence of antagonist microorganisms.

23. MANAGEMENT AND CONTROL Difficult to control and no single strategy has shown 100% efficiency in control of the disease so far. Bactericides (copper) and antibiotics (streptomycin, ampicillin, tetracycline and penicillin) have shown little efficiency on suppression in the field. A combination of diverse control methods, including host resistance, cultural practices, and the use of chemical or biological control should be used in an integrated pest management approach to control where the pathogen is established. Chemical control by soil fumigation (chloropicrin) or application of phosphorous acid is also expensive to apply. Biological control, based on use of R. solanacearum antagonists, and use of suppressive soils has shown promising results at the small experimental scale, but still needs to be validated at a larger scale.

24. Care should taken : Before Plantation Consider an effective weed control in and around tomato fields and aquatic weed control around irrigation ponds. Apply 3-4 years rotation and cover crops for infested fields to reduce R. solanacearum, weeds and nematodes. Do not irrigate rotation and cover crops with R. solanacearum contaminated pond or surface water, avoid reinfestation. Use well drained and leveled fields and do not use low-lying areas of the field. Raise soil pH to 7.5-7.6 and increase available calcium (liming). Consider using infested fields (after 3-4 years rotation) during cooler months for tomato production.

25. Care should taken: During production Exclude the pathogen by applying strict sanitation practices (pathogen free irrigation water, transplants, stakes, machinery,etc.) Chlorinate your irrigation water continuously if you are using surface water or R. solanacearum infested pond water . Continue an effective weed control in and around tomato fields and irrigation ponds. Irrigate based on water need, avoid over irrigation.

26. Care should taken: After Harvest Plow under crop residue immediately. Start with suitable rotation and cover crops (i.e., rye for winter,sorghum for summer) to avoid weeds that support R. solanacearum populations .

27. BACTERIAL SPECK ( Pseudomonas syringae pv. tomato ) SYMPTOMS Leaf symptoms appear as dark brown to black spot often surrounded by yellow hallow. Black lesions with yellow borders can also occur on leaf margins where guttation droplets collect. Large area of leaf tissue are killed as these lessions coalesce. Oval to elonagted black lessions occur on stem and petioles. Fruit lessions remain small(1mm),speck like and superficial,however they can be larger and sunken. On immature fruit they are surrounded by yellow hallow.

28. CONDITIONS FOR DISEASE DEVELOPMENT Cool weather( 13-25°C),rainy weather or sprinkler irrigation. One day of leaf wetness is required for disease development. The organism survive on roots and leaves of many crops and weeds. Seed can be infested.

29. MANAGEMENT AND CONTROL Use of resistant varieties. Copper sprays. Furrow or drip irrigation should apply when possible. Remove diseased plant debris. Reduce activity in field when plants are wet. Use seed dipped in hot water.

30. EARLY BLIGHT ( Alternaria solani ) SYMPTOMS Foliar symptoms generally occur on the oldest leaves and start as small, brownish to black lesions. These leaf spots enlarge up to1.3 cm in diameter in a concentric fashion. The area around the spot may become yellow, as may entire severely affected leaves. Under favorable conditions, significant defoliation of lower leaves may occur, leading to sunscald of fruit. Dark lesions enlarge in a concentric fashion.Mature lesions in fruit are typically covered by a black velvety mass of fungal spores. Stem lesions are dark, slightly sunken and enlarge concentrically. Basal girdling and death of seedlings may occur (collar rot).

31. DISEASE CYCLE AND EPIDEMIOLOGY Infection by the fungus is most rapid under warm (28-30°C) wet conditions. Survives between crops in plant debris and on seed. It can also survive on volunteer tomato plants (warm climates) and on other cultivated and wild solanaceous plants (potato, eggplant, horse nettle and black nightshade). Early blight symptoms (leaf spot and defoliation) are most pronounced in the lower canopy. Disease severity and prevalence are highest when plants are loaded with fruit.

32. DISEASE MANAGEMENT CULTURAL CONTROLS Use pathogen-free seed and transplants. Maintain plant vigor through adequate irrigation and fertilization to increase disease resistance. Use long rotations away from tomato and other solanaceous crops, avoid planting tomato near related crops that are more mature and eliminate weed hosts. Avoid plant injury which allows entry of the pathogen and spread of the fungus through adequate insect management.

33. CHEMICAL CONTROL Contact fungicides such as chlorothalonil and mancozeb provide moderate levels of control when applied preventively. Newer chemistries including strobilurin fungicides (azoxystrobin, pyraclostrobin, etc.) have provided excellent control in university trials.

34. RESISTANCE MANAGEMENT New fungicide chemistries including the strobilurins generally have a narrow mode of action and are prone to the development of resistance by fungi; rotate these with fungicides from different groups. Adequate resistance to early blight has not been identified in tomato cultivars.

35. LATE BLIGHT ( Phytophthora infestance ) INTRODUCTION Not a true fungus, but rather is regarded as a fungus like organism. Classified as an Oomycete,order Personosporales contains Phytophthora species . Worldwide distribution, but most severe epidemics occur in areas with frequent cool, moist weather. The host range is mainly limited to solanaceous crops, including tomato, nightshade (Solanum nigrum) and potato. Sweet potato (Ipomea batatas) is not a host for late blight.

36. SYMPTOMS On tomato leaves : Lesions begin as indefinite, water-soaked spots that enlarge rapidly into pale green to brownish-black lesions and can cover large areas of the leaf. On the abaxial surface of the leaf may be covered with a gray to white moldy growth (not to be confused with powdery mildew disease). As the disease progresses, the foliage turns yellow and then brown, curls, shrivels, and dies. On tomato petioles and stems : Lesions begin as indefinite,watersoaked spots that enlarge rapidly into brown to black lesions that cover large areas of the petioles and stems. During wet weather, lesions may be covered with a gray to white moldy growth of the pathogen. Affected stems and petioles may eventually collapse at the point of infection, leading to death of all distal parts of the plant.

37. Infected tomato fruits turn greasy, olivaceous-brown, decay, and can shrivel up and fall off the plant and never ripen. Such infected fruits are not fit for human consumption. They should be removed from affected gardens and destroyed. The fruit damage that appears in this photograph can occur in a few days or less under the right weather conditions.

38. MANAGEMENT AND CONTROL Select a tomato variety that reaches maturity quickly. Stake up tomato plants, especially indeterminate types. Keep tomato stems and branches away from the ground. Plant blight-resistant tomato varieties when they become available. Intercrop tomato with non-susceptible host plants, preferably non-solanaceous plants. Practice good crop sanitation; inspect the plants regularly and remove diseased material from the plot . Destroy volunteer tomato plants. Avoid moving through the tomato garden or field when plant foliage is wet. Control solanaceous weeds around the tomato garden.

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