Late blight of potato is a serious fungal disease caused by Phytophthora infestans. It is identified by expanding blackish-brown leaf lesions that cause the leaves to become necrotic and rot. The fungus favors cool, moist environments and spreads rapidly via wind and rain. It can damage and rot leaves, stems, and tubers. Effective control measures include using disease-free seed, removing plant debris, applying fungicides at early symptoms, and harvesting in dry conditions.

1. Late blight of potato
AGRICULTURE PLANT DISEASES

2. description
 Late blight of potato is identified by blackish/brown
lesions on leaves and stems that may be small at
first and appear water-soaked or have chlorotic
borders but expand rapidly and the entire leaf
becomes become necrotic.
 Late blight (phytophthora infestans) fungus is in the
same genus as the fungus causing pink rot.
 Blight can spread very quickly, carried by wind and
rain.

3. Phytophthora infestans
 Phytophthora infestans is an oomycete or water
mold, a fungus-like microorganism that causes the
serious potato and tomato disease known as late
blight or potato blight.
 Early blight, caused by alternaria solani, is also
often called "potato blight".
 The organism can also infect some other members
of the solanaceae.
 The pathogen is favored by moist, cool
environments: sporulation is optimal at 12–18 °c (54–
64 °f)

5. Systematic position
Phytophthora infestans
Order: Peronosporales
Family: Peronosporaceae
Genus: Phytophthora
Species: P. infestans

6. Symptoms
damages leaves, stems and tubers
 Affected leaves appear blistered as if scalded by hot water and
eventually rot and dry out. When drying out, leaves turn brown or
black in color.
Affected stems begin to blacken from their tips, and eventually dry
out.
Severe infections cause all foliage to rot, dry out and fall to the
ground, stems to dry out and plants to die.
Affected tubers display dry brown-colored spots on their skins and
flesh. This disease acts very quickly. If it is not controlled, infected
plants will die within two or three days.

7. Symptoms
Dry rot Wet rot
 Dry and brittle timber appearance  Wet and spongy to the touch
 There may be orange spore dust  Affected timbers will appear darker
 White strands on timbers  Localised fungal growth
 White or grey cloud-like structures on
timbers
 Affected timber is vulnerable to
shrinkage
 Rusty brown fruiting bodies  More likely to be accompanied by a
damp, musty smell

8. Spread of late blight potato
The spores are carried by wind and rain to healthy plants, where the
disease cycle begins again.
A disease cycle can occur every five to seven days, resulting in rapid
spread and movement of late blight.
Tubers are infected by spores washed from lesions to the soil.

9. Survival from late blight potato
Use potato tubers for seed from disease-free areas to ensure that the
pathogen is not carried through seed tuber.
The infected plant material in the field should be properly destroyed.
Grow resistant varieties like Kufri Navtal.
Fungicidal sprays on the appearance of initial symptoms.

10. Epidemiology
 Cool (12 to 15°C) and humid ( above 90 %) weather with rain
alternating with warm (20° C) moist period.

11. Fungus
• Mycelium - endophytic, coenocytic and hyaline
• Sporangiophores – arise from internal mycelium through stomata on
the tubers
• Sporangia - multinucleate, thin walled, hyaline, oval shaped
• Zoospores - biflagellate Phytophthora infestans A, zoospores
produced within the lemon-shaped sporangia

12. Life cycle of potato late blight

13. 1. Use of healthy seed
2. Removal of plant debris (field sanitation)
3. Removal of weeds
4. Harvesting in dry season
5. Harvesting after ripining
6. Remove upper portion before 15 days of harvesting
7. Earthing- 10-15 cm
Control measure of late blight of potato