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Bush Beans Contender: Identification of Plant Disease

Bean    South Africa

I have sown (direct) Contender bush beans on 31 October, with germination starting around 6 November. The plants are now on average 15cm high. I have done preventative spraying for red spider mite on 10 Nov - applying Makhro Seizer 100 and Makhro SK Eco Oil. The application was done early morning - no direct sunlight. I, however, noticed some leaves on a few plant looking sickly with "bruised"-like areas that appeared like damaged plant cells. To me, this looks like an early form of blight and I have this morning sprayed Efekto Virikop.

Can anyone perhaps help identify what it is and the cause, so that I can take corrective action.

I have 300 plants in an area of 14sqm (14m x 1m) planted in three parallel rows. Plants 10-15cm apart and rows 30cm apart.

UPDATE
Since the last posting, the situation is worsened and most of the plants now show similar damage to the leaves. I have added new photos to show this. The damage appears on the first growth of leaves - the second set is now appearing and I would like to stop this spreading to this new growth.

Chris


Posted by: Chris (2 points) Chris
Posted: November 15, 2017

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Hi Chris, is there any drastic change in temperature, especially during night? It looks like a cold injury to me. Usually the Common blight disease (caused by bacteria- Xanthomonas campestris pv. phaseoli) symptoms "appears as small translucent water-soaked spots on the leaf. As these spots enlarge, this tissue dies leaving brown spots with a narrow yellow margin. Lesions are often large and irregular in shape. In some cases, a yellowish discharge may be observed. Water-soaked sunken lesions can be present on pods. These pod lesions later turn brownish-red. Bacteria may infect the vascular system and kill the main stem and branches."

http://www.extension.umn.edu/garden/y...

https://springerplus.springeropen.com...


Posted by: Dr. Ravishankar Narayana (134 points) Dr. Ravishankar Narayana
Posted: November 16, 2017

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Chris commented,
Ravishankar, yes we have had some very strange weather patterns over the past few weeks. It's the beginning of summer after a very dry winter (we are in a winter rainfall area) and day and night temperatures have ranged widely over the past weeks with temperatures of 38 degrees Celsius the one day, down to 16-17 the next. We are not in a frost area. What you suggest makes sense and I'll watch the situation carefully over the next week or so. Plant growth has been very good, as mentioned, and corresponds with last season's growth patterns.
8 months ago.



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I would disagree to Dr. Ravishankar Narayana, I have met such symptoms caused by Pseudomonas aptata.


Posted by: alex ignatov (33 points) alex ignatov
Posted: November 17, 2017

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Dr. Ravishankar Narayana commented,
Thanks for your input Alex. Is it possible to share some images? It will be really helpful for us and growing community.
8 months ago.

alex ignatov commented,
@Ravishankar, sorry, I made many pics of sugarbeet plants with P. aptata, but beans were not my target. I have isolated the pathogen only.
Alex

8 months ago.



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