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Beans can be affected by a fungal disease called rust. Heavy attacks may reduce plant vigour and hence yield but, thankfully, the attack often develops too late to have a serious effect.
Bean rust is a fungal disease of the foliage, spread by airborne spores. Infection is favoured by wet weather conditions.
You may see the following symptoms:
High levels of bean rust tend to develop quite late in the season (after mid-summer), and often have little effect on yield. However, prolonged spells of wet or humid, warm weather throughout the summer will increase the risk of infection.
Rust on Phaseolus beans is caused by the fungus Uromyces appendiculatus. It is unrelated to broad bean rust that is caused by the fungus Uromyces viciae-fabae and infects Vicia beans.
The rust fungi are described as biotrophs; that is, they grow within the living tissues of the plant and extract nutrients from the cells. Although they do not kill tissues rapidly, heavy attacks by rusts can cause tissues to collapse and die prematurely and this is the case with the bean rusts. Some rusts require two different plant hosts in order to complete their life cycle but both of the bean rusts spend their entire life on the bean host.
The different coloured pustules seen on the plants as the summer progresses are the result of the rust fungi producing different types of spore. The brown pustules contain summer spores that can spread the disease very rapidly under suitable wet weather conditions, whilst the black pustules contain overwintering spores. These can survive on leaf debris to affect the following season’s crop.
Broad beanBroad bean chocolate spotBroad bean rustBroad bean seed beetleDisposing of diseased materialFrench beansRunner beansRunner beans: failure to set pods
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anonymous on 01/10/2014
My climbing French beans have developed rust. I have been letting the pods mature to save and dry the beans to eat. The advice is not save them to sow next year but will they be OK to eat?
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