This is a post I would have preferred not to write, for it describes a plant disease I haven’t seen before and, quite frankly, don’t want to see again.

At the end of July we had four days of rather cool, rainy weather and soon after this, on 29th July, I noticed that our neighbour’s runner beans looked sickly. They had reddish-brown marks on the leaves (especially on the veins) and on the stems. The plants hadn’t started to produce bean pods. I searched on the internet and what I found suggested that the plants were infected with Bean Anthracnose. I ruled out Bean Rust (caused by the fungus Uromyces appendiculatus) – this appears as reddish-brown, raised pustules on the bottom of leaves. The article ‘Anthracnose and rust of garden beans‘ on the University of Minnesota Extension website shows the difference.

Bean Anthracnose on Runner Beans, late July

My neighbour agreed with my diagnosis and immediately destroyed her plants and put them in our council green waste collection, for composting at high temperatures. (Putting diseased beans on a normal garden compost heap won’t destroy the fungus, as the temperature won’t be high enough.)

Another month went by and one of my varieties of Climbing French Bean (‘Blue Lake‘) started to show characteristic spots on its pods, which I removed and destroyed. The disease has now spread to the Climbing French Bean ‘Neckarkoningin’ and the Heritage variety ‘Bird’s Egg’ is slightly affected. Heritage varieties ‘Caroline’s Purple’, ‘Poltetschka’ and ‘Bonne Bouche’ appear to be unaffected. As before, I have removed the affected plants, including shed leaves.

Bean Anthracnose on Climbing French Beans, October

This is the first time I have seen Bean Anthracnose. The book ‘Pests, Diseases and Disorders of Garden Plants’ (Stefan Buczacki and Keith Harris, Harper Collins, 1998) says that the disease is widespread on dwarf and less severely on runner beans, but usually only apparent in cool, wet summers. However, epidemics of the disease can occur in bean growing areas of the world with frequent rainfall, such as central and western New York State. In Brazil, India, China, Mexico, Myanmar, Canada, Argentina and the United States, anthracnose is considered to be one of the most invasive and destructive bean diseases and can destroy up to 95% of yield.

Bean Anthracnose is transmitted in the seed, a discovery made in 1921 by M. F. Barrus of Cornell University. Recommendations to prevent the spread of the disease include removing dead bean plants and their debris at the end of the growing season, digging over the soil so any residues are buried and following crop rotation so that beans aren’t grown in the same place for at least two years. This is all common sense, but the main inconvenience for me is that I won’t be able to save this year’s dried beans for planting next year.

There are quite a few resistant varieties of bean. The Garden Organic website lists ‘Forum’ (from Thompson & Morgan) and ‘Copper Teepee’ (from Mr Fothergill and Johnsons) and the Crocus website recommends ‘Aramis’.

Hopefully, this year has been a one-off. It is certainly the first time I’ve seen Bean Anthracnose in sixteen years of growing French and Runner Beans on my allotment.