This presentation covers the major diseases affecting pea (Pisum sativum), focusing on their causal agents, symptoms, disease cycles, and management strategies. Emphasis is placed on accurate identification, epidemiology, and integrated management practices. Key concepts include pathogen identification, symptomatology, disease cycle, epidemiology, and integrated disease management.
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.