Bacterial: pea blight

Pseudomonas syringae pv. pisi

List of symptoms/signs
Fruit  -  lesions: black or brown
Leaves  -  necrotic areas
Leaves  -  yellowed or dead
Seeds  -  discolorations
Stems  -  discoloration of bark
Symptoms on peas may be found on all aerial plant parts, including stipules, leaflets, petioles, stems, tendrils, flower buds and pods, but those on stems and stipules are the most characteristic.
In dry weather, with occasional frost, symptoms usually appear on the stem near the soil as water-soaked and later olive-green to purple-brown spots. The infection extends upwards to the stipules and leaflets, veins turn brown or black and adjacent tissues become diseased in a fan-like pattern. The interveinal tissues may become watersoaked and then turn yellowish to brown, before finally drying out and becoming papery.
In wet weather, lesions on leaflets and pods begin as small, round, oval or irregular dark-green water-soaked spots at first but later enlarge and coalesce. They are sharply defined by the veins. A cream-coloured bacterial ooze may be found on the lesion surface which, on drying, gives a glossy appearance. The leaflets later become yellowish and the spots brown and papery. Ripening pods become twisted and dry and have sunken, greenish-brown lesions. Lesions on the pod may be limited to a narrow band on the sutures. When pod invasion is mainly along the dorsal suture, the seed inside may be covered with bacterial slime. Infected seeds show a water-soaked spot near the hilum and/or are shrivelled, with a brownish-yellow discoloration. Infection often takes place on sepals and spreads to the flowers and flower buds may be killed before they open.
If the infection spreads all over the plants, they may wither and die. Under warm dry climatic conditions, however, the infection stops and the upper parts of the plants remain green and produce healthy flowers and pods. This may also be true for new axillary growth from the base of diseased plants.

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