Bean mosaic virus?

[Jang]

I have probably at least a quarter of my bean varieties, both dwarf and climbing showing signs of some kind of disease. It started with just a bit of yellowing but as the plants have matured some have quite severe symptoms.

The most likely diagnosis seems to be bean mosaic virus which apparently is carried sometimes through infected seed and otherwise by aphid. I've seen no sign of aphid infestation on any of the beans but I imagine it doesn't have to be an infestation and there are probably other ways to can be transferred. It seems that some varieties are resistant, especially more recent ones and certainly I have very healthy looking beans right next to sick looking ones. In most cases all the plants of one variety are similarly infected.

I'm wondering whether anyone else has experience of this virus and can confirm the diagnosis. If so, how persistent has it been. I suppose I should take strong measures and pull up all the infected beans but they are producing beans and it will be a wrench!

[Galina]

Does not quite have the puckering that goes with mosaic virus, although first photo bottom left shows a leaf with two colour green that is suspect. Maybe Leafspot or rust? Here is a guide to bean diseases https://www.canr.msu.edu/uploads/fil...n_Diseases.pdf

[Jang]

Thanks, a really clear and well illustrated guide.
I'm hoping and returning to the idea that it might be magnesium deficiency as suggested a short time ago by triffid. It could perhaps be caused by rather heavy use of rotted horse manure which was perhaps over rich in another element which works against the plants' ability to take up magnesium. Spraying with magnesium sulphate has been suggested on a bean forum so I might try that though I'm instinctively sceptical about most such 'treatments'.

[triffid]

If it is Mg deficiency then foliar Mg sulphate should rectify the issue quite quickly. Too much potassium can affect the absorption of Mg and zinc. But it is strange how only some of the plants are unwell.

[Jang]

Thanks. I’ve administered the Epsom salts treatment so will wait hopefully. I guess the foliage watering should be repeated after a few days?

Elsewhere it’s been suggested that some varieties are more susceptible to Mg deficiency than others, as with the virus, but certainly the difference is very marked.

[triffid]

Sorry only just saw your question. But I haven't a clue! Have you observed any improvement?

[Jang]

It’s very difficult to say. It certainly hasn’t got any worse and the bean pods aren’t distorted. On the other hand, I’ve had some unexplained fairly sudden deaths which is rather worrying.
Russel Crow has suggested elsewhere that once I have dried beans of an afflicted variety I should try a second sowing and see whether the problem is passed on. Whether I can get them advanced enough within this season to show up I’m not sure, but as I would be sending him some back I’m hoping to give that a try.

[Galina]

Jang, just an observation I would like to share with you. I am growing Haricot de Rocquencourt this year. The seeds were pretty old and I direct seeded them. Never expected brilliant germination but every one came up. They were very tightly packed. So I took the outer ones and planted them with proper spacing. The packed ones have the yellowing that yours have, the spaced out ones are nice and green. Same beans, one set dark green the other yellow and blotchy. Does not impact the yield surprisingly, but the ones with proper spacing look much healthier. Wanted to share that with you.

[Jang]

Thanks Galina, that's interesting and also reassuring. I have still puzzled over the behaviour of my beans this year. Some plants died prematurely but a few have thrown up healthy green foliage somewhat later in the season. Following your experience, it's possible that they had more space at this point as the earlier ones had died off or at least lessened in vigour.
I guess there's always some variation in the prospering of different plants but this year I've been more hyper-alarmed at plants which don't prosper because of fears raised.

In the event, he majority of varieties have yielded a good amount of seed and there doesn't seem to be any of the kind of pod distortion you'd expect from virus-infected plants except that some haven't developed fully - but then perhaps that's always the case and usually simply accepted.

I still won't share any seed from this year's crop just in case, and next season's growing (without manure and more widely spaced!) will perhaps settle the case one way or the other.

Viruses eh.....!