Pisum sativum
Powdery Mildew (fungus – Erysiphe polygoni): Plants infected with this fungus are covered with a white powdery mold on the leaves, stems and pods. Infected plants are stunted and eventually die. The fungus is seed-borne. Optimum temperatures for development are between 68oF and 75oF. Soils should be kept as dry as possible yet will permit maximum growth. Avoid heavy application of fertilizer and rotate with non-related crops. Powdery mildew is the most serious disease of English peas in Texas.
Bacterial Blight (bacterium – Pseudomonas syringae pv. pisi): The bacterium attacks all parts of the plant. Infected stems become olive brown in color, while the leaflets become yellowish or water-soaked. Young infected pods drop prematurely. Well formed pods become water-soaked. The bacterium is seed-borne. Rain or irrigation water is necessary for movement of the organism. After infection takes place, four to six days is required before lesions are visible. Optimum temperature for development is 82oF. Control of this pathogen is through a combination of practices such as drainage, row spacing, seeding rates, weed control, and restricting irrigation only to that needed for maximum plant growth.
Ascochyta Blight (fungi – Ascochyta pisi, A. pinodella, A. pinodes): All three fungi are known to attack peas. Affected leaves have spots which are large, pale brown to dark brown in color. Lesions are papery in appearance and have gray to tan centers marked by small black pycnidia. Infection by some species cause purple lesions. On pods, deep lesions are formed which may have purple margins. The center is tan with black pycnidia. Planting infected seed results in poor stands. All three species of fungi are seed borne and carry over in crop residue. Rainfall and heavy dews are necessary for infection. No infection occurs when the relative humidity is below 80%. Optimum temperatures for the fungus are between 68oF and 82oF. Control is achieved by using clean seed, long rotations (four years or longer), planting in well-drained soil, and deep plowing to remove old crop residue.
Aphanomyces Root-Rot (fungus – Aphanomyces euteiches): Early infection causes complete crop loss due to seedling death. Late infection results in poor plant growth and reduced seed formation. Tissue decay does not develop above the soil line unless the weather is extremely wet. Infection occurs in both wet and dry soils, but is most destructive in wet soils. Optimum temperatures for infection are between 65oF and 75oF. The use of high levels of fertilizer will encourage continued root development. Nitrogen acts as a suppressant to fungal growth. The use of three year rotation, well-drained soil, and the liberal use of fertilizer will help reduce losses from this disease. Mosaic (virus): Irregular, light and dark, greenish areas and puckering occurs in leaves. Control aphids that transmit the virus.
Charcoal Rot: (See Section on Charcoal Rot)
Root Knot: (See Nematode)
