TOMATO - FUNGUS
LATE BLIGHT
Pathogen: Phytophthora infestans
Host range: Tomato and potato may be severely affected.
Importance: Late blight is a most destructive disease of tomato, damaging both leaves and fruits. The pathogen spreads very quickly in cold and rainy weather. It occurs in all European countries and also in tropical and subtropical regions where tomato is cultivated at higher altitudes.
Under favourable conditions, leaves very rapidly die without previous yellowing.
33. Figure: Phytophthora infestans
Source: project number: HU/02/B/F/PP-136012
Symptoms:
When infested by late blight, leaves typically turn browning and necrotic and a brown, dry rot develops on the fruits. The first symptoms usually appear on leaf tips and margins where drops of water persist as indefinite water-soaked lesions. Infested leaves turn necrotic very quickly as the disease progresses, usually without any yellowing, and plants may die in a matter of a few days. In the mornings or after long wet periods, the sporangiophores may form a white layer on the underside of leaves, on the border between healthy and necrotized areas.
34. Figure: Phytophthora infestans
Source: project number: HU/02/B/F/PP-136012
Stems and petioles can also be affected; the disease manifests here in the form of dark brown spots. Infected fruits bear dark, olivaceous spots which may cover the entire fruit. At the beginning, these spots are dry to the touch, but secondary infections by other microorganisms may result in wet rot. A white layer of sporangiophores may also appear on fruits if weather is cold and wet, usually at the end of summer.
The symptoms of late blight may be confused with those of Alternaria. Main differences: the spots caused by Alternaria are darker, usually smaller and, most importantly, they feature concentric rings. Alternaria prefers a warmer and drier weather, compared to late blight.
35. Figure: Phytophthora infestans
Source: project number: HU/02/B/F/PP-136012
Late blight on fruits. When the fruit is only infested by Phytophthora infestans, the flesh stays rather firm; however, secondary infections may lead to the development of soft rot. White mycelial growth may also be present on infected parts in wet and cold weather.
36. Figure: Phytophthora infestans
Source: project number: HU/02/B/F/PP-136012
Late blight inside the tomato fruit. Note the dry rot and the white mycelial growth.
37. Figure: Phytophthora infestans
Source: project number: HU/02/B/F/PP-136012
Disease cycle: The overwintering oospores of the fungus in potato tubers and potato plants are probably the only source of infection. Overwintering as oospores in tomato plant debris has not been proven for all European countries. From potato stands and volunteer plants, sporangia are carried to tomato plants by wind. Sporangia form at high humidity (90-100 %), when the temperature is between 3-26 °C. Tissue infection only takes place in the presence of water, through either the upper side or underside of leaves. Zoospores released from sporangia germinate the most rapidly at 12-15 °C, but their further development requires temperatures above 20 °C. This is why cool nights combined with warm days are ideal for late blight development. If humidity is not so high, sporangia behave as conidia i.e. a single infective hypha emerges from them. Temperatures above 30°C are unfavourable for the fungus.
Control:
The main method of protection is the application of effective fungicides, but some other methods may also be helpful.
Cultivation practices:
- avoid cultivation in wet localities (closed valleys, vicinity of forests and water surfaces) sunny fields should be preferred; sunshine is particularly important in the morning to dry the dew from the plants,
- keep the canopy upright and provide for adequate spacing so that air can move freely among the plants.
- if possible, avoid overhead irrigation,
- do not grow tomato in the vicinity of potato,
- remove and destroy infected plants,
- varieties: the leaves of some varieties are partially resistant, yet the fruits can be infected. Consult your seed dealer.
- chemical control (new systemic fungicides e.g Azol and sulphuric plant protection products)
EARLY BLIGHT
Pathogen: Alternaria solani
Host range: Potato and tomato.
Importance: Early blight occurs wherever tomatoes are grown, but it causes severe damage in a few regions only.
Symptoms: At the early stage, Alternaria spots are characterised by concentric rings and they are rather dry. Later on, the spots may be invaded by secondary microorganisms and develop wet rot. Early blight usually attacks older fruits at the beginning of ripening. Early blight on an older leaflet, in the early stage. Note the dark brown spots with concentric rings.
38. Figure: Alternaria solani on leaf
Source: project number: HU/02/B/F/PP-136012
39. Figure Alternaria solani on leaf
Source: project number: HU/02/B/F/PP-136012
40. Figure Alternaria solani brown spot on leaf
Source: project number: HU/02/B/F/PP-136012
41. Figure Alternaria solani on fruit
Source: project number: HU/02/B/F/PP-136012
Disease cycle: A.solani usually survives in plant debris and on seeds, although in regions with mild winters volunteer plants, potato and Solanaceous weeds may also serve as overwintering hosts. Heavy dew or frequent rains favour the germination of spores. Temperatures between 25-30 °C are optimal for disease development.
Control:
- avoid overhead irrigation, if possible,
- crop rotation,
- use pathogen-free seeds,
- proper fertilization,
- the most effective control is provided by fungicides. Use fungicides complying with EU regulations, e.g. Polyram DF contact treatment or material containing metiram as active ingredient.
DAMPING OFF
Host range: A broad range of cultivated dicot plants.
Importance: Damping off is a very common condition that severely affects transplants.
Symptoms: Seedlings fail to emerge or a large number of them suddenly die. The stems and leaves of young plants appear water soaked and soft. Often, they become discoloured, greyish or brown. Young leaves wilt. Roots are missing or covered with brown lesions.
Disease cycle: The fungi causing damping off easily survive in soil and plant debris and on improperly cleaned and sanitized tools, equipment etc. used in the previous growing season. Pythium in particular is often transmitted by contaminated tools and hands. Spores may by carried by the wind and infect plants from splashing water (rain, irrigation).
Control: General sanitation methods are of paramount importance. When growing transplants, use clean, sterilized pots, tools and medium. Do not use garden soil. The planting medium should be light and fast draining. Provide for sufficient air circulation and illumination. When planting outdoors, make sure the temperature has reached the optimal range for young plants. Irrigate in the early hours so that the plants can dry before the evening.
LEAF SPOT OF TOMATO
Importance: A devastating and globally occurring disease of tomato, able to infest plants at any stage of their development.
Symptoms: The spots caused by Septoria typically appear on the older leaves first. The disease then spreads upwards, towards the younger parts. The spots are circular or somewhat angular, 2-5 mm in diameter, with dark brown margins and lighter brown to grey centres (they look like rings). Unlike those caused by early blight, Septoria spots do not have concentric rings.
42. Figure Septoria lycopersici
Source: project number: HU/02/B/F/PP-136012
- crop rotation (avoid plant members of the family Solanaceae )
- thoroughly eliminate sources of inoculum (plant debris) after harvest
- in large fields, plant debris may be incorporated into the soil by deep ploughing
- use healthy, disease-free seeds/transplants
- avoid overhead irrigation; water plants early in the day
- fungicides are effective against the disease. The use of fungicides depends on the rate of infection, and the on the plant protection products complying with EU regulations.
43. Figure Botryotinia fuckeliana
Source: project number: HU/02/B/F/PP-136012
44. Figure Botryotinia fuckeliana
Source: project number: HU/02/B/F/PP-136012
"Ghost rings" caused by grey mould. In some varieties, the inside parts of the rings ripen later than the surrounding tissue. Not to be confused with the symptoms caused by Tomato spotted wilt virus.
45. Figure Botryotinia fuckeliana
Source: project number: HU/02/B/F/PP-136012
- increasing the calcium content of soil reduces susceptibility,
- proper spacing of plants,
- sunny locality,
- avoid overhead irrigation wherever possible,
- application of fungicides in compliance with EU regulations.
FUSARIUM WILT OF TOMATO
Pathogen: Fusarium oxysporum f. sp. lycopersici
Host range: The pathogen is the fungus Fusarium oxysporum f. sp. lycopersici, which infects the roots of tomato and, to a lesser extent, pepper and eggplant.
Importance: Fusarium is a fairly common disease of tomato. The pathogen damages vessels, blocking circulation in the water transporting system, and hence causing the infected plants to wilt, temporarily first (only for a day) and then permanently.
46. Figure Fusarium oxysporum f. sp. lycopersici
Symptoms:
Young plants turn yellow when infected:
47. Figure Fusarium oxysporum f. sp. lycopersici
48. Figure: Fusarium oxysporum f. sp. lycopersici
Disease cycle: Fusarium produces conidia. It may survive in the soil for several years. The conidia are spread by water, insects and infected tools. Warm weather provides optimum conditions for development and reproduction; the fungus is favoured by soil temperatures around 27oC or higher.
Control: The production of resistant varieties should always be considered.
Plant debris or even the soil itself may serve as sources of infection.a) Mechanical control:
Remove and destroy infected plants and disinfect utensils. Proper crop rotation is advisable
b) Biological control:
Use of resistant species is advisable
c) Chemical control:
Use plant conditioners, and fungicides permitted for use in tomato in the EU.
VERTICILLIUM WILT
Host range: Veticilium . dahliae has a very wide host range among economically important crops and ornamental plants, native species and weeds, including both woody and herbaceous plants. (CABI 2020)
The primary economic hosts of Verticilium. dahliae include: artichoke, aubergine, bell pepper, potato, strawberry and tomato and etc.
49. Figure Distribution of Verticillium dahliae Kleb.
50 Figure: Verticillium dahliae Kleb. symptoms on leaves
51. Figure Verticillium dahliae Kleb. symptoms on leaves
Disease cycle: Verticillium dahliae is soil borne. While not a true soil dweller, it can persist in the soil for up to 15 years in the form of masses of hardened mycelium known as microsclerotia. The fungus penetrates the water transporting vessels in the root tip and then invades the entire plant, through the vascular system.
Control:
Chemical control and crop rotation are ineffective.
Cultivation practices
- Use healthy transplants and avoid Vd-infested areas.
- Use tolerant cultivars.
- Grafting on resistant/ tolerant rootstocks
Biological control:
Treat the soil with Trichoderma species combined with bacteria that break down cellulose and lignin.
Listo of Viruses:
- TOMATO LEAF CURL NEW DELHI VIRUS (ToLCNDV)
- PEPINO MOSAIC VIRUS (PepMV)
- TOMATO TORRADO VIRUS (ToTV)
- TOMATO CHLOROSIS VIRUS (ToCV)
- TOMATO INFECTIOUS CHLOROSIS VIRUS (TICV)
- TOMATO BROWN RUGOSE FRUIT VIRUS (ToBRFV)
- TOMATO STOLBUR PHYTOPLASMA
- BACTERICAL CANKER
- BACTERIAL SPECK AND BACTERIAL SPOT
- BACTERIAL WILT
- LATE BLIGHT
- EARLY BLIGHT
- DAMPING OFF
- LEAF SPOT OF TOMATO
- GREY MOLD
- FUSARIUM WILT OF TOMATO
- VERTICILLIUM WILT
- LOW TEMPERATURE, PHOSPHORUS DEFICIENCY
- LEAF CURL
- CATFACES
- CALCIUM DEFICIENCY
- RUSSETING
- POTASSIUM DEFICIENCY - YELLOW TOP
- SUNSCALD
- TOMATO LEAF MINER
- SOUTHERN GREEN STINKBUG
- RED TOMATO SPIDER MITE
- THRIPS
- COTTON BOLLWORM
- GREENHOUSE WHITEFLY, SILVERLEAF WHITEFLY
- TWO-SPOTTED SPIDER MITE
- COLORADO POTATO BEETLE
- ROOT-KNOT NEMATODES
- POTATO CYST NEMATODE