Alan
McNab
Professor of Plant Pathology |
|
| Peas:
Blight Diseases |
| Blights
of greatest signifigance are Ascochyta blight and bacterial
blight. |
|
|
Ascochyta
Blight is caused by any of three Ascochyta spp. of fungi. Symptoms
develop on stems, roots, leaves and pods. Black to purplish streaks
develop on stems. Streaks are more conspicuous at the nodes and they
enlarge into brown or puplish irregular-shaped areas from the root
zone to about 10 inches up the stem. Root-rot symptoms are as described
for Ascochyta root rot. Leaf spots are gray to purplish and may be
very small and irregular or large and circular. Dark concentric rings
sometimes form in leaf spots. Severely affected leaves may shrivel
and die. Pod spots are gray to purplish, lack concentric rings, and
are sunken. The blight-causing fungi are seed-borne. Abundant rainfall
favors disease development and spread |
|
|
Bacterial
Blight, caused by the bacterium Pseudomonas pisi affects all
above-ground plant parts. Seedlings from infected seed may die. On
older plants, water-soaked spots develop on pods, stems, and leaves.
In wet weather, spots enlarge and a white to crea-colored slimy ooze
may collect on the spot surface. In dry weather, leaf spots dry up,
turn brown, and become papery. Disease-causing bacterial overwinter
in seed and are introduced into fields bia seed. The bacteria probably
do not overwinter in residue from diseased plants. |
|
){kind=link}
){kind=link}