Tomato Diseases
Late Blight
Symptoms
- Water-soaked black lesions on leaves and stems.
- Lesions expand rapidly and the entire leaf becomes necrotic.
- White sporulation (sporangia and sporangiophores) on leaves.
- Dark brown lesions on fruit.
- Soft rot and disintegration of fruits.
Identification
- Causal organism:Â Phytophthora infestans (Mont.) de Bary
- Asexual spores:Â Indeterminate sporangiophores, Zoospores: Biflagellate with one tinsel flagellum directed anteriorly and one whiplash flagellum directed posteriorly
- Pathogen:Â Hyaline and coenocytic
- Sexual spores:Â Thick-walled oospore
- Survival and Mode of Spread
> Survival:Â Infected Debris
> Primary spread: Infected debris
> Secondary spread: Wind
- Favourable conditions:
> Cool nights, warm days and extended wet conditions from rain and fog
> Sporangia formed when RH is ¡ 90%
> Optimum temp for sporulation is 18 - 22oC
Management
- Proper drainage
- Crop rotation
- Soil application of Trichoderma asperellum (viride) @ 1.0 kg/ac
|
Fungicide |
Dosage |
|---|---|
|
200 ml/acre |
|
|
 5 ml/lit |
|
|
  1-1.5 kg/acre |
|
|
200 ml/acre |
