Powdery mildew Erysiphe pisi is rarely seen in the field in Western Australia. Warm humid conditions favour its growth late in the season.
What to look for
Plant
Infected plants are covered with a white powdery film, and severely infected foliage is blue-white in colour; tissue below these infected areas may turn purple.
All aerial parts of the plant may become infected resulting in withering of the whole plant.
Severe pod infection can cause a grey-brown seed discolouration that lowers the quality of the grain.
Where did it come from?
Contaminated stubble
The fungus oversummers on infected pea trash and produces spores which are blown by wind into new crops.
The disease may also be seed-borne, but this source of infection is less important.
Under favourable conditions, the disease may completely colonise a plant in 5-6 days. Once a few plants become infected, the disease rapidly spreads to adjacent areas. Warm (15-25°C), humid (over 70% RH) conditions for 4-5 days late in the growing season, during flowering and pod filling, favour disease development. However, heavy rainfall is not favourable for the disease as it will actually wash spores off plants. Night time dews are sufficient for the disease to develop
Management strategies
Rotation
It can be controlled through crop rotation, variety selection and strategic use of foliar fungicides, but these are unnecessary in Western Australia.
