This presentation provides an in-depth overview of major diseases affecting brinjal (eggplant), focusing on their pathogens, symptoms, epidemiology, and management strategies. Emphasis is placed on the biology of the causal agents, disease cycles, and integrated approaches for effective control. Understanding these aspects is crucial for sustainable brinjal production and minimizing crop losses.
Little Leaf Disease of Brinjal
- Caused by Phytoplasma, an ovoid to spherical pathogen localized in phloem sieve tubes.
- Characterized by small, yellow, soft leaves with shortened petioles and internodes, giving a bushy appearance.
- Axillary buds enlarge but remain stunted; flowering is rare and flowers, if present, remain green.
- Fruiting is uncommon; any formed fruits are hard, necrotic, and often mummified.
- Pathogen survives in weed hosts and is transmitted mainly by jassids (Hishimonas phycitis) and less efficiently by Empoasca devastans.
Epidemiology and Management of Little Leaf Disease
- Collateral hosts include Datura spp., Vinca rosea, Argemone mexicana, chilli, tomato, and tobacco.
- Disease cycle involves survival in weed hosts and transmission by insect vectors.
- Management includes use of tolerant varieties (Pusa Purple Round, Pusa Purple Cluster, Arka Sheel).
- Destruction of infected plants and eradication of solanaceous weeds are essential.
- Chemical control: Spray methyl demeton (2 ml/L) or apply phorate granules; seed dip in tetracycline (10–50 ppm) recommended.
Bacterial Wilt of Brinjal
- Caused by Ralstonia solanacearum, a Gram-negative, motile rod with polar flagella.
- Race 1 infects solanaceous crops (tomato, eggplant) and some non-solanaceous hosts.
- Symptoms include sudden wilting, leaf epinasty, yellowing, stunting, and browning of vascular tissues.
- Whitish bacterial exudate may be observed from cross-sections of infected stems.
Epidemiology and Management of Bacterial Wilt
- Pathogen is both soil- and seed-borne, surviving in plant debris, wild hosts, and weeds.
- Spread occurs via irrigation water, infested soil, and contaminated tools.
- Favored by high soil moisture and temperature.
- Management: Grow resistant varieties (Pant Samrat, Arka Nidhi, Arka Neelakantha, Surya, BB 1, 44, 49).
- Practices include crop rotation with non-solanaceous crops, green manuring (Brassica spp.), soil solarization, and biological control (Pseudomonas fluorescens, Bacillus spp., Erwinia spp.).
Integrated Management of Bacterial Wilt
- Nursery: Treat seeds with talc-based Pseudomonas fluorescens (10g/100g seed); apply to nursery soil (50g/kg soil).
- Main field: Dip seedlings in P. fluorescens or Bacillus subtilis suspension (25g talc formulation/L water) for 20–30 minutes before transplanting.
- Drench leftover solution around root zones (50 ml/plant) to enhance protection.
Phomopsis Fruit Rot (Blight) of Brinjal
- Severe in tropical and subtropical regions; first reported in India (Gujarat, 1935).
- Pathogen produces septate, hyaline mycelium; pycnidia become erumpent with age.
- Conidia are of two types: alpha (subcylindrical) and beta (filiform, curved); perfect stage forms perithecia with bicelled ascospores.
- Attacks all growth stages, causing damping-off in nurseries, collar rot in young plants, and fruit rot in mature plants.
Symptoms and Epidemiology of Phomopsis Fruit Rot
- Leaf symptoms: Circular to irregular grayish-brown spots with light centers; yellowing and premature leaf drop.
- Stem lesions: Dark brown, oval, with grayish centers and pycnidia; can cause cankers and plant toppling.
- Fruit symptoms: Pale, sunken spots that enlarge and become watery, leading to soft rot and mummification.
- Pathogen is seed-borne and survives in plant debris as mycelium and pycnidia.
- Dissemination via rain splash, irrigation, tools, and insects.
Management of Phomopsis Fruit Rot
- Remove and destroy diseased crop debris to reduce inoculum.
- Practice crop rotation and summer ploughing to minimize pathogen survival.
- Use disease-free seed; hot water treat seed at 50°C for 30 minutes.
- Seed treatment with thiophanate methyl (1g/kg seed) recommended.
- Spray thiophanate methyl or carbendazim (0.1%) twice at 20-day intervals for effective control.
Cercospora Leaf Spot of Brinjal
- Caused by Cercospora spp., leading to significant yield losses under high humidity.
- Symptoms: Large, circular to irregular brown or grayish-brown leaf spots; coalescence leads to premature leaf drop and occasional fruit rot.
- Fungus survives in infected plant debris and seeds; warm days, cool nights, and high humidity favor disease development.
- Transmission facilitated by moist wind, irrigation water, and insects.
Management of Cercospora Leaf Spot
- Adopt cultural practices: Destroy crop debris, rotate crops, use disease-free seeds, and maintain wider plant spacing.
- Initiate fungicidal sprays (zineb 0.25%, carbendazim 0.1%, or thiophanate methyl 0.1%) at disease onset.
- Repeat sprays at 10–14 day intervals for sustained protection.
Objective Questions
Q1. Which pathogen is responsible for little leaf disease in brinjal?
A. Phytoplasma
B. Ralstonia solanacearum
C. Cercospora melongenae
D. Phomopsis vexans
Answer: A
Q2. Which vector is considered a less efficient transmitter of little leaf disease in brinjal?
A. Hishimonas phycitis
B. Emposca devastans
C. Bemisia tabaci
D. Myzus persicae
Answer: B
Q3. Which management practice is NOT recommended for bacterial wilt of brinjal?
A. Use of resistant varieties like Pant Samrat and Arka Nidhi
B. Green manuring with Brassica species
C. Spraying methyl demeton
D. Soil solarization with transparent polyethylene sheet
Answer: C
Q4. What is the main symptom of Phomopsis fruit rot on brinjal fruits?
A. Small pale sunken spots that enlarge and cover the fruit surface
B. Water-soaked lesions with concentric rings
C. Powdery white growth on fruit surface
D. Black streaks along the fruit
Answer: A
Q5. Which of the following is NOT a collateral host for little leaf phytoplasma in brinjal?
A. Datura fastuosa
B. Vinca rosea
C. Brassica juncea
D. Argemone mexicana
Answer: C
Q6. Which of the following is a recommended seed treatment for managing Phomopsis fruit rot in brinjal?
A. Tetracycline 10-50 ppm
B. Hot water at 50°C for 30 minutes
C. Carbendazim 0.5% for 10 minutes
D. Copper oxychloride 0.2%
Answer: B
Q7. Which environmental condition most favors the development of Cercospora leaf spot in brinjal?
A. High humidity and heavy persistent dews
B. Low temperature and dry weather
C. High soil salinity
D. Alkaline soil pH
Answer: A
Q8. Which symptom is characteristic of bacterial wilt in brinjal?
A. Sudden wilting and death of infected plants
B. Mosaic pattern on leaves
C. Leaf curling and stunting
D. Brown pustules on stems
Answer: A
Q9. Which of the following is NOT a management strategy for little leaf disease in brinjal?
A. Destruction of affected plants
B. Eradication of solanaceous weed hosts
C. Crop rotation with solanaceous crops
D. Seed dip in tetracycline
Answer: C
Q10. Which type of conidia produced by Phomopsis fruit rot pathogen has an unclear role in disease epidemiology?
A. Alpha conidia
B. Beta conidia
C. Gamma conidia
D. Delta conidia
Answer: B
