Diseases of tomato

early blight and late blight in tomato

1. PRESENTED BY – SHILPA C BAITAEO71 III B.Sc II Sem B Section DISEASES OF TOMATO

2. FUNGAL DISEASES OF TOMATO DISEASE CAUSAL ORGANISM EARLY BLIGHT Alternaria solani LATE BLIGHT Phytophthora infestens WILT Fusarium oxysporium f.sp.lycopersici Verticillium wilt BUCK EYE /FRUIT ROT Phytopthora nicotianae var. parasitica SEPTORIA LEAF SPOT Septoria lycopersici POWDERY MILDEW Levillula taurica DAMPING OFF Pythium aphanidermatum

3. BACTERIAL DISEASES OF TOMATO DISEASE CAUSAL ORGANISM BACTERIAL WILT Ralstonia solanacearum BACTERIAL LEAF SPOT Xanthomonas vesicatoria

4. VIRAL DISEASES OF TOMATO DISEASE CAUSAL ORGANISM LEAF CURL Tomato leaf curl virus Vector – white fly TOMATO MOSAIC Tobacco mosaic virus Vector – aphid TOMATO SPOTTED WILT Tomato spotted wilt virus Vector - thrips

5. CONTENT : Early blight Late blight

6. Early blight - Alternaria solani Early blight is the most destructive disease of tomatoes in the  tropical  and  subtropical  regions. Each 1% increase in intensity can reduce yield by 1.36%, and complete crop failure can occur when the disease is most severe.Yield losses of up to 79% have been reported in the U.S., of which 20-40% is due to seedling losses (i.e., collar rot) in the field. It can affect almost all parts of the tomato plants, including the leaves, stems, and fruits. The plants may not die, but they will be weakened and will set fewer tomatoes than normal.

7. Leaves Initially small dark spots form on older foliage near the ground Leaf spots are round, brown and can grow up to half inch in diameter. Larger spots have target board or bull eye symptom like concentric rings and tissue around spots often turns yellow. Severely infected leaves turn brown and fall off, or dead, dried leaves may cling to the stem Stem Seedling stems are infected at or just above the soil line. The stem turns brown, sunken and dry ( collar rot ). If the infection girdles the stem, the seedling wilts and dies. Stem infections on older plants are oval to irregular, dry brown areas with dark brown concentric rings. Fruit Fruit can be infected at any stage of maturity Fruit spots are leathery, black, with raised concentric ridges and generally occur near the stem Infected fruit may drop from the plant.

8. FAVOURABLE CONDITION : Disease develops at moderate to warm 15 to 27 degree celsius ; Rainy weather or heavy dew, 90% humidity , June-July sowing - weak and old plants prone to infection high soil moisture. DISEASE CYCLE : PSI : Mycelium or conidia in infected plant debris. SSI : Conidia by wind, water or rain splash . Mode of spread: Seed borne and air borne conidia

9. spore L ight brown conidia with muriform shape, but the isolates varied in the size (length, width and beak length) of the conidia, the number of cells per conidium and sporulation times. Among the nitrogen sources, potassium nitrate followed by sodium nitrate and ammonium molybdate increased the growth of mycelium . Low pH (4-4.5) was found as ideal for the growth of  A. alternata ,  while the minimum growth was observed in pH 9.0, irrespective of isolates The conidia of  A. alternata   isolates germinated at 46°C.

10. DISEASE CYCLE

11. MANAGAMENT CULTURAL CONTROL Use pathogen-free seed, or collect seed only from disease-free plants . Remove infected debris from field to reduce inoculum for the next year. Water plants in the morning so plants are wet for the shortest amount of time. Apply plastic or organic mulch to reduce humidity and provide a barrier between contaminated soil and leaves . Use a drip irrigation than over head system to minimize leaf wetness which provides optimal conditions for fungal growth. Rotate to a non- Solanaceous  crop for at least three years. If possible control wild population of  Solanaceae . This will decrease the amount of inoculum to infect your plants. Closely monitor field, especially in warm damp weather when it grows fastest, to reduce loss of crop and spray fungicide in time.

12. IIHR 2101 ( Solanum habrochaires LA-1777) showed highly resistant reaction, IIHR- 2758 showed moderately resistant reaction Fertilize properly to maintain vigorous plant growth. Particularly, do not over-fertilize with potassium and maintain adequate levels of both nitrogen and phosphorus . For greenhouse production, early blight has been reduced by as much as 50% by covering houses with UV-absorbing vinyl film. Increase air circulation in rows. Damp conditions allow for optimal growth of  A. Solani  and the disease spreads more rapidly. This can be achieved by planting farther apart or by trimming leaves. CHEMICAL CONTROL Some of the fungicides are chlorothalonil , copper product,mancozeb , potassium bicarbonate, and ziram . Bacillus subtilis FORECAST MODEL EPIDEM

13. LATE BLIGHT- Phytophthora infestens Late blight is a potentially devastating disease of tomato and potato, infecting leaves, stems, and fruits of tomato plants. The disease spreads quickly in fields and can result in total crop failure if untreated. Late blight of potato was responsible for the Irish potato famine of the late 1840s . phytophthora  in Latin means "plant destroyer." Infected plant tissue dies.

14. Signs and symptoms : Leaves : Leaves have large, dark brown blotches with a green gray edge; not confined by major leaf veins Infections progress through leaflets and petioles, resulting in large sections of dry brown foliage. Stem : Stem infections are firm and dark brown with a rounded edge. Fruit : Firm, dark brown, circular spots grow to cover large parts of fruits. Spots may become mushy as secondary bacteria invade. In high humidity, thin powdery white fungal growth appears on infected leaves, fruit, and stems In cool, wet weather, entire fields turn brown and wilted as if hit by frost.

15. FAVOURABLE CONDITIONS: High relative humidity >90 % Low temperature 10 – 25 degree celsius Cloudy weather and rainfall with splashing rains. DISEASE CYCLE : PSI : Oospores in the infected debris and soil. SSI : Sporangia or zoospores dispersed by wind or rainwater Mode of spread : Soil borne-spread through sporangia or zoospores dispersed by wind or rainwater.

16. MANGEMENT : CULTURAL METHOD Destroy potato piles before the growing season begins, Control volunteer potato plants, as infected plants can grow from infected tubers. Seed infection is unlikely on commercially prepared tomato seed or on saved seed that has been thoroughly dried . If infection is found in only a few plants within a field, infected plants should be removed, disced -under, killed with herbicide to avoid spreading through the entire field Movement of water from infected to healthy field should be avoided. Crop rotation with cereals Late Blight-Resistant Tomato Varieties ‘ Meru ’ and ‘ Kiboko ’

17. CHEMICAL CONTROL Prophylactic sprays with copper fungicides or dithiocarbomates 0.25% . Metalxyl / amiston 0.2%. FORECAST MODEL : TOMCAST