The Blackfoot may be a tribe of Indians in North America, but here it's a nasty sickness that has gotten into a few of my potatos. It is called Zwartbenigheid in dutch; literally translated into english that would be, "Blacklegness". I know, I know--I can see you smiling now, but I don't have any idea what it is called in english, so the literal translation looks and sounds a little silly, I reckon. Well, I can tell you, this disease is not a silly one at all. It can be very contageous and quickly ruin one's crop and the crops of the neighbours. Zwartbenigheid is an illness that occurs when the temps are moderately cool (±19°C is the optimum temp where the sickness begins to develop and manifest itself). The lower stem begins to rot and turning black, a process that eminates from the seed potato. The blackness can not only be seen in the portion of the stem most proximal to the seed potato, but can involve the entire stem. One hallmark of this sickness is the fishy odor that the infected stems give off once pulled out of the ground. The leaves turn light green and curl inwards from the outer edges, eventually yellowing and withering. The bacteria, Erwinia carotovora subsp. atroseptica; as far as is known, only infects potatos. Originally the tubers become infected during the harvesting process by coming in contact with other tubers that are already infected. They can also become infected when the foliage is being destroyed. Of course, further contamination can be spread from plant to plant by spattering rain as well as insects. There isn't alot that one can do to combat this bacterial insult in a conventional sence, ie spraying or dusting...what you must do is to remove all infected 9yellow/light green) stems, foliage when the disease is detected, and remove the tubers at harvest time (including the 'mother' tuber and isolate and destroy all this. Take special care to wash and and clean your digging tool thoroughly as well as your hands, once the removal process has been completed. Harvest only when the ground is good and dry. Preventative measures are not so numerous either: order your seeding potatos from a reputable firm (and do not use storebought or small potatos that you have raised yourself). Keep an eye out for this in your patch, the foliage will be light green or yellow and the plant 'stunted' in contrast to it's neighbours. I am mentioning this because of the coolish weather that we have had this spring.
So sorry to hear you lost some of your crop Sjoerd. We have had cold wet weather too and I have some plants with the same sort of symptoms...namely Impatiens. I have had to rip them out of all the beds (22 or so flats worth!)Don't even get me started on the Blackspot! I hope you don't lose any more potatoes Sjoerd.
Oh heck I hope that disease doesn't spread to your whole crop Sjoerd. Do you have to sterilize the soil after you've dug up the infected plants? I guess you won't be using the company that supplied those seed potatoes again.
Thanks for your well-wishes, Eileen and Netty. There have only been three plants involved so far. Fingers crossed that there shall be no more. I check them several times a day now. Actually, I was a fool to plant any of those sick spuds. I thought that I had weeded out the bad ones. Oh well, that's greed for you. :-? There are some related Erwinia strains that do infect other plant types. It's a nasty germ.
