Farming News - Chocolate spot in field beans, Field bean rust, Powdery mildew in peas alerts

Chocolate spot in field beans, Field bean rust, Powdery mildew in peas alerts

23 Jul 2020
Agronomy / Frontdesk / Arable

Chocolate spot in field beans

Following recent wet weather, some field bean crops have developed chocolate spot infections. Chocolate spot is favoured by overcast, wet and humid conditions, leading to small round chocolate coloured lesions at the beginning of infection, and followed by larger, coalescing lesions under suitable conditions. The disease can cause premature defoliation and yield loss due to the reduction of photosynthetic leaf area.

Field bean rust

Bean rust is favoured by warm days and cool, humid nights. Later maturing spring planted beans are often at more risk of infection. The disease appears as orange to red-brown pustules on the leaves, becoming prolific in suitable conditions, and stems may also become infected. Severe infections may lead to premature defoliation, and poor pod formation and development.

The following active substances will give good control of chocolate spot and rust:

Active substance




Azoxystrobin + tebuconazole

Custodia; Seraphin

Boscalid + pyraclostrobin

Signum; Insignis; Pyrabos

Cyprodinil + fludioxonil

Botrefin; Button; Clayton Gear; Modif; Shift





Powdery mildew in peas

Powdery mildew infection is favoured by warm days and cool, humid nights. Later sown peas are more susceptible to infection, which is observed as a powdery white mildew on the upper surface of pea leaves. The infection spreads quickly to cover the whole plant. Severe infection can cause failure of pod fill, delay maturity and lead to high dust levels during combining. 

Vining peas may be blemished, and the disease can cause an unpleasant odour that affects the flavour of the peas. There is some varietal resistance to the disease and sulphur applied regularly as a foliar spray reduces infection.