Introduction to Pea Diseases
- Pea (Pisum sativum) is susceptible to several fungal diseases.
- Major diseases include Fusarium wilt, powdery mildew, downy mildew, rust, and Ascochyta blight.
- Effective management requires understanding pathogen biology and disease epidemiology.
Fusarium Wilt – Pathogen and Symptoms
- Caused by Fusarium oxysporum f. sp. pisi.
- Initial symptoms: drooping, yellowing, and premature leaf drop.
- Pod formation is severely affected; collar region shows necrosis and discoloration.
- Dark brown vascular discoloration visible in stem cross-section.
Fusarium Wilt – Disease Cycle and Management
- Pathogen survives in soil for long periods; infects via root hairs.
- Primary infection: soil, seed, water; secondary: conidia via rain splash.
- Favored by soil temperatures of 23–27°C and warm weather.
- Seed treatment with carbendazim (2 g/kg) and soil drenching with copper oxychloride (0.25%) recommended.
Powdery Mildew – Pathogen and Symptoms
- Caused by Erysiphe pisi.
- Appears as white powdery spots on leaves, stems, and pods.
- Severely infected leaves become chlorotic, distorted, and may fall.
- Pods may be small and malformed.
Powdery Mildew – Disease Cycle and Management
- Spread by airborne spores; thrives in warm (15–25°C), humid (>70%) conditions.
- Cultural control: use resistant varieties, destroy infected stubble, avoid adjacent sowing to previous pea fields.
- Chemical control: sprays of benomyl, carbendazim, sulphur, or triadimefon as per recommended doses and intervals.
Downy Mildew – Pathogen and Symptoms
- Caused by Peronospora viciae.
- Grayish-white mold on lower leaf surface; yellowish area on upper side.
- Infected leaves turn yellow, die; stems may be stunted and distorted.
- Brown blotches and mold may develop on pods.
Downy Mildew – Disease Cycle and Management
- Primary infection: soil, seed, water; secondary: sporangia via rain splash or wind.
- Favored by high humidity and low temperatures (5–15°C).
- Remove and burn diseased plants promptly to reduce inoculum.
Rust – Pathogen and Symptoms
- Caused by Uromyces pisi.
- Initial symptoms: leaf flecking, progressing to reddish-brown pustules.
- Pustules merge, burst, and release brown spores; severe cases cause plant drying and yield loss.
Rust – Disease Cycle and Management
- Survives on infected plant debris and alternate hosts (e.g., Euphorbia).
- Favored by frequent precipitation, dew, and temperatures of 20–25°C.
- Cultural control: destroy debris, crop rotation with non-legumes, mixed cropping.
- Chemical control: sulphur or triadimefon sprays as per recommendations.
Ascochyta Blight – Pathogens and Symptoms
- Caused by Ascochyta pisi, A. pinodes, and A. pinodella.
- Symptoms: purplish-brown flecks on lower leaves, stems, tendrils; lesions enlarge and coalesce.
- Severe infection causes foot rot (purplish-black lesions at soil line), lodging, and pod lesions.
- Pod infection leads to small, discolored, or shrunken seeds.
Ascochyta Blight – Disease Cycle and Management
- Ascospores spread by wind; conidia by rain splash.
- Primary infection from diseased seed or soil debris.
- Favored by warm, humid conditions (15–25°C).
- Use resistant varieties (e.g., B-90, CDC Frontier, CDC Luna), seed treatment with thiabendazole, and crop rotation.
Summary: Integrated Disease Management in Pea
- Combine cultural, chemical, and genetic resistance strategies for effective control.
- Use certified disease-free seed and resistant varieties.
- Practice crop rotation and field sanitation.
- Apply fungicides judiciously based on disease monitoring and recommendations.