1. Tomato Diseases Fungal Bacterial Viral
Fruit Anthracnose - Colletotrichum spp.
Fusarium Wilt - Fusarium oxysporum
Verticillium Wilt - Verticillium dahliae, V. albo-atrum
Early Blight - Alternaria solani
Late Blight - Phytophthora infestans
Septoria Leaf Blight - Septoria lycopersici
Soil Rot of Fruit - Rhizoctonia
Bacterial
Bacterial Spot - Xanthomonas campestris pv. vesicatoria
Bacterial Speck - Pseudomonas syringae pv. tomato
Viral
Cucumber Mosaic Virus

2. Fusarium Wilt
Fusarium is a soil-inhabiting fungus that invades the vascular system of the plant and interrupts the passage of nutrients and water to the above-ground parts, causing wilting symptoms.

3. Fusarium Wilt
The vascular tissue in this slide is discolored due to infection by the Fusarium fungus. Healthy vascular tissue is white to light green.

4. Fusarium Wilt
This slide shows the Fusarium fungus growing out of the infected stem tissue in a laboratory test.

5. Verticillium Wilt
Verticillium is another soil-inhabiting fungus that causes a wilt in tomato. Symptoms are quite similar to those of Fusarium wilt. A laboratory test is necessary for positive diagnosis.

6. Tomato Diseases - Fusarium and Verticillium Wilts - Key Points
Pathogens: Fusarium oxysporum, Verticillium dahliae, V. albo-atrum
Soil-borne pathogens
Survive in soil for several years
Plants generally infected through roots

7. Tomato Diseases - Fusarium and Verticillium Wilts - Control Strategies
Rotation (at least 2-3 years)
VF or VFN resistance

8. Septoria Leaf Spot
This is an extremely destructive foliage disease of tomato. Symptoms begin on the foliage closest to the ground and then move on up the plant. Wet, humid weather increases the severity of the disease that can progress to the point where all the foliage is killed and all that is left are green or ripe fruit exposed to the sun.

9. Septoria Leaf Spot
Leaf spots tend to be circular, with dark borders and gray or tan centers. With the use of a hand lens one can see the small black pycnidia in the center of these lesions. These pycnidia produce the fungal spores, that serve as inoculum that attack new leaves.

10. Tomato Diseases - Septoria Leaf Blight Key Points
Pathogen: Septoria lycopersici
Survives over winter on infected plant debris, and also on equipment, stakes and cages
Spores dispersed by splashing water (rain, irrigation), workers or equipment moving through wet plants
Favored by moist, warm weather
Symptoms generally appear first on lower leaves

11. Tomato Diseases - Septoria Leaf Blight Control Strategies
Rotation (at least 1-2 years)
Thorough sanitation of equipment, stakes, etc.
Stake plants
Plastic mulches
Fungicide sprays
Several effective fungicides available
Apply at least weekly when weather favorable for disease
Good coverage, especially of lower leaves, crucial
Carefully read label directions

12. Early Blight
This disease is similar to Septoria blight but is caused by the fungus Alternaria. It too starts on the lower foliage and can completely defoliate the plant.

13. Early Blight
The leaf lesions of this blight are more uniformly brown without the light center as found with Septoria. Yellowing of the leaf tissues surrounding the lesions is due to a toxin produced by the pathogen.

14. Early Blight
A closer look at the lesions show the characteristic target-like pattern. The fungus sporulates on all the parts of the necrotic tissue. Lesions generally do not cross over major veins, but may coalesce to form larger dead areas on leaflets.

15. Tomato Diseases - Early Blight Key Points
Pathogen: Alternaria solani
Survives on infected plant debris - partially buried debris is an excellent source of inoculum
Spores wind dispersed, can be carried long distances
Greatest threat of infection:
Fields with short rotations
Planting adjacent to fields infected previous year where debris not completely buried
Infection occurs first on oldest leaves

16. Tomato Diseases - Early Blight Control Strategies
Plant rotation - minimum of at least 2-3 years between solanaceous crops
Potato, tomato, weeds in nightshade family excellent hosts
Completely bury plant debris after harvest
Fungicide applications
Several effective fungicides available
Carefully read label directions
Provide adequate nitrogen
Avoid excessive irrigation

17. Late Blight
This disease is caused by the same pathogen that causes late blight in potato; Phytophthora infestans. Leaf infections are manifested by irregular lesions that initially appear water-soaked, becoming darkly necrotic and spread rapidly to cover large areas. During humid weather, one can observe the cottony mass of fungal hyphae extruding out of the stomates on the lower surface of the leaflet along the edge of the lesion margin when necrotic tissue meets healthy tissue.

18. Late Blight
Tomato fruit infected with the late blight fungus exhibit dark greasy and roughened areas of the fruit skin (epidermis).

19. Tomato Diseases – Late Blight Key Points
Pathogen: Phytophthora infestans
Same fungus that causes late blight of potato
Isolates may differ in ability to infect potato and tomato
Both mating types (A1 and A2) are now found in WI
Symptoms:
Lesions on leaves initially water-soaked spots with irregular borders
Lesions turn pale green, then brown to almost black
White fungal growth appears on underside of leaves at border between necrotic and healthy tissue
Petiole and stem symptoms similar – lead to rapid death of plant

20. Tomato Diseases – Late Blight Key Points
Source of inoculum:
Cull piles of infected potatoes or tomatoes
Infected tomato transplants
Infected plants in neighboring fields
Hairy nightshade
Favored by rain, high relative humidity
Control Strategies
Destroy cull piles, and weed hosts
Plant disease-free tomato transplants
Protectant fungicides – several effective fungicides available

21. Fruit Anthracnose
While infection can occur while the fruit is still green, symptoms do not appear until the color change occurs and the fruit begin to soften. Fruit lesions are circular and slightly sunken, as if someone pressed one’s finger against the ripening fruit.

22. Fruit Anthracnose
As the lesions enlarge, black microsclerotia form in the bottom of the lesion. Under moist conditions the lesions may be covered with masses of pink-colored spores. Secondary organisms can invade the tissue enhancing the breakdown of the fruit.

23. Tomato Diseases - Fruit Anthracnose Key Points
Pathogen: Several species including Colletotrichum coccodes, C. dematium and C. gloeosporioides
Favored by wet weather and warm temperatures
Survives in soil and plant debris several years
Spores splashed by rain or irrigation onto foliage and fruit
Ripe or overripe fruit most susceptible, symptoms progress rapidly

24. Tomato Diseases - Fruit Anthracnose Control Strategies
Rotation (at least 2 years)
Weed control (eliminates alternate hosts)
Stake plants
Mulches
Optimum plant spacing
Remove and destroy infected fruit
Fungicide sprays

25. Tomato Diseases - Fruit Anthracnose Control Strategies
Fungicide sprays
Several effective fungicides available
Start when first fruit reaches size of a quarter
Continue weekly until harvest
Read labels carefully
Examples of label requirements:
rate of application
seasonal use limitations - amount / acre / season
pre-harvest intervals
crops that can be grown in treated area next year

26. Bacterial Spot
This disease is not common in Wisconsin, but a few incidents of it’s appearance are reported every year. Circular water-soaked spots up to 1/8 inch in diameter occur on the leaflets, eventually turn brown.

27. Bacterial Spot
Xanthomonas campestris pv. vesicatoria infection on fruit begins with small, blister-like spots. As spots enlarge up to 1/8 inch in diameter, they assume a scab-like appearance.

28. Bacterial Speck
Leaf lesions are small, round, dark brown to black dots and with time, display a halo. This bacterial disease is caused by Pseudomonas syringae pv. tomato.

29. Bacterial Speck
On the fruit the lesions are very tiny and dark. The pathogen is seed-borne but can be spread from plant to plant by splashing rain or implements and machinery.

30. Tomato Diseases - Bacterial Spot and Speck Key Points
Pathogens:
Bacterial speck: Pseudomonas syringae pv. tomato
Bacterial spot: Xanthomonas campestris pv. vesicatoria
Favored by high humidity, rainfall/irrigation
Pathogens seed borne
Dispersal - wind driven rain, clipping plants, equipment moving between wet plants
Optimum temperature:
Bacterial speck: ° F Bacterial Spot: ° F

31. Tomato Diseases - Bacterial Spot and Speck Control Strategies
Clean transplants, pathogen-free seed
Plant rotation - at least 1-2 years between solanaceous crops
Thoroughly incorporate plant debris after harvest
Application of bactericides
Fixed coppers - alone or in combination with fungicides
Heavy rain, wind-driven rain, hail decrease efficacy

32. Buckeye Rot
This rot usually occurs when the tomato fruit is in contact with the soil since the fungal pathogen, Phytophthora parasitica, is a soil inhabitant. Typical symptoms include concentric rings of light and dark brown tissue. Decay follows. Do not plant tomatoes in poorly drained soils. Mulch well around the base of the plants to protect the fruit from contact with the soil.

33. Soil Rot
Alternating light and dark brown colored concentric rings characterize this disease. The soil fungus Rhizoctonia infects the fruit as it lies on the soil. As the fungus advances into the fruit, it causes a decay along with other secondary organisms. Mulch well around the plant to prevent fruit contact with the soil.

34. Tomato Diseases - Soil Rot of Fruit Key Points
Pathogen: Rhizoctonia solani
Symptoms:
Rotted tissue showing concentric bands of alternating dark and light brown
Initially, rotted area is firm but becomes mushy with invasion of soft rotting organisms
Affected areas eventually turn black
Overwinters in soil
Fungus enters tomato where fruit contacts soil
Symptoms may not be evident at harvest but can develop in storage or shipment

35. Tomato Diseases - Soil Rot of Fruit Control Strategies
mulching around base of plants to avoid fruit contact with soil helps prevent infection
mulches include straw, grass clippings, paper, plastic
staking or caging of plants helps to avoid fruit contact with soil

36. Tobacco Mosaic Virus
Contrasting light and dark green areas in a mosaic pattern are symptoms of this viral disease. Fruit symptoms are generally lacking, but yield reduction both in size and number may occur. Resistant cultivars are available.

37. Tomato Diseases – Tobacco Mosaic Virus (TMV) - Key Points:
Pathogen: Tobacco Mosaic Virus
Symptoms:
Light and dark green mottled areas on leaves
Necrosis of fruit with some strains
Stunting of plants depending on growth stage at infection
Virus easily transmitted by workers, machinery
TMV may be present in tobacco products
Virus survives on equipment, in plant debris

38. Tomato Diseases – Tobacco Mosaic Virus (TMV) - Control Strategies:
Crop rotation – minimum of 3 years
Workers should wash hands in detergent before handling plants
Sanitize pruning equipment periodically
Use cultivars with TMV resistance

39. Cucumber Mosaic Virus
The mosaic pattern is similar to that caused by tobacco mosaic virus. With more severe infection stunting occurs and the leaflets take on a “shoestring” appearance. Severe infection causes a serious decrease in fruit production. Fruit that are produced are small in size and maturity is delayed.

40. Tomato Diseases – Cucumber Mosaic Virus (CMV) - Key Points:
Pathogen: Cucumber Mosaic Virus
Symptoms - foliar:
Mosaic or mottle similar to symptoms produced by TMV
“Shoestring” appearance of leaves (filiform or threadlike)
General stunting of the plant
Symptoms – fruit:
Yield reduction – amount and size of fruit
Fruit often misshapen
Delay in maturity
Numerous strains of the virus exist – many are specific to tomato
Over 700 plant species are host to this virus
Usually spread by aphids

41. Tomato Diseases – Cucumber Mosaic Virus (CMV) - Control Strategies:
Eliminate weed hosts – such as
Milkweed
Chickweed
Ragweed
Clover
White cockle
Carpet weed
Plant a non-host barrier (such as corn) around the tomato crop

42. Double Streak Virus
When tobacco mosaic virus and potato virus X infect a tomato plant at the same time the disorder is called “Double Streak Virus”. Stem symptoms include necrotic streaks of various lengths and widths. Leaflets collapse and wilt.

43. Double Streak Virus
Fruit symptoms of Double Streak consist of light brown spots. Sanitation is the most important means of preventing this disease. Workers who smoke should be directed to wash their hands well with soap and water. Any symptomatic plants should be removed and destroyed.

44. Blossom End Rot
This is a physiological problem rather than a pathogenic one. A calcium deficiency in the blossom end of the fruit is responsible for this problem. Externally, tissue at the blossom end of the fruit collapse and turn black, usually giving the fruit a flattened black bottom. Affected tissues may be invaded by secondary fungi and bacterial leading to a soft rot of the fruit. Calcium deficiency in the fruit does not necessarily mean that the soil is deficient. Fluctuations in available water can cause this disorder. Mulch around the base of plants in order to keep the moisture supply constant. Irrigate when necessary.

45. Catface
This problem can be caused by a number of factors. Frost or cold temperatures at the time of pollination resulting in partial fertilization is one of them. High nitrogen or extensive pruning or exposure to herbicides have also been implicated.

46. Growth Cracks
Pictured here is “radial” cracking. Some cultivars are more susceptible to this phenomenon than others. It relates to the strength and stretch capacity of the skin (epidermis) of the fruit. Moisture amount and temperature fluctuations influence cracking. The cracks can be colonized by secondary rotting organisms. Less cracking occurs if the fruit is shaded from the hot sun by adequate foliage. Resistant cultivars are available.

47. 2,4-D Injury
The herbicide 2,4-D used in the area can be carried in on wind currents and cause distortion. This herbicide has growth regulating properties and can cause excessive cellular growth, twisting and distortion. Be mindful that spray drift can originate from as far away as several miles. Symptoms can be confused with those caused by virus infection.

48. Juglone Toxicity
Walnut and butternut trees produce a toxin called juglone. Tomato plants are among plant species that are particularly susceptible. All the parts of the tree contain the toxin and when the roots of the tomato plant come in contact with the roots, stems, leaves, or nuts of the walnut tree, the toxin is taken up by the tomato and wilting results. Plant well away from the dripline of the walnut or butternut tree. Even if the tree has been cut down, the remaining roots continue to contain the toxin. The tomato plants in this slide are between the corn and beans. Note the trunks of the walnut trees in the upper center of the slide.

49. Juglone Toxicity
This tomato plant is one from the row of plants from the previous slide. Wilting is apparent. Other symptoms can include growth stunting, yellowing and discoloration of vascular tissues similar to the Verticillium and Fusarium wilts described earlier.