Someone on our site has potato blight and has not removed the dead bits. Does this means it will spread? Unfortunately I am down wind.
Several of the plants have spots on the leaves but one of the plants is very dead and another not far behind.
Someone else has something suspicious on their tomatoes and they also have not removed those leaves. Plants still growing strongly so not sure about these.
Should I ask them to remove the problem or will it make no difference.
There are so many beautiful potato plants on our site it will be devastating if they all die.
I'd be very surprised if there is any blight around yet. I live in the one of the warmest parts of the country and we have only had one Smitth period here in mid-May.
A lot of people seem to be confusing the normal process of early potatoes dying back because the plants are spent with blight.
I will take a photo. They look pretty sick to me.
There is a lot of potato watering going on round here, I think they are creating their own damp patch.
Please make sure to photograph both the top and the underside of the same leaf
The latest strain of blight does not require a smith period and is doing the rounds now. Best thing you can do is spray your own potatoes to combat the problem.
Quote from: Tattieman on June 19, 2009, 22:41:58
The latest strain of blight does not require a smith period and is doing the rounds now.
Do you have a reference or more details of this please tattieman? I've just checked the Potato Council blight maps and they are showing the whole country clear except for one confirmed case in volunteer potatoes and one confirmed case on an outgrade pile. Both of these are in the far south-west of Cornwall.
Early blight will be almost everywhere now but as it is easier for us to control it will not be reported on a commercial scale as it is not affecting any growers yet.
The new strain 13 is now getting a grip and sppraying every 7 days is required to beat it as the life cycle of the disease is the quickest yet.
it also seams to survive at lower temps and doesn't need a smith period to attack crops. If I get any more info about it I will post it.
http://www.fwi.co.uk/Articles/2009/04/05/114942/new-blight-strain-demands-extra-vigilance.html
Depressing reading... :'(
Sorry for the delay finally managed to get down to the allotments with a working camera. Battery ran out on me.
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This is elsewhere on the site and it different affects the whole row and no black on stem.
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There is some possibility that the damage was caused by being sat on by a toddler.
The fact that they are hanging in there implies it isn't blight to me... :-X
The first things that strikes me is that those shoots which are badly affected do not show any indications of blight commensurate with their being so affected.
Pots 1 shows what appears to be a classic case of magnesium deficiency, with green veins, interveinal chlorosis, patches of interveinal necrosis, and withering.
Pots 4 shows one stem (lower stem in the lower left quadrant) which appears to have blackleg, but this may be just a trick of the light. One stem shows a spot, which does not look the right colour for blight, and is not where one would expect a blight spore to lodge
Pots two shows one background plant with two or three leaves with odd dark spots on them - these appear to be on slightly chlorotic leaves, but the markings do not (at distance) look like magnesium deficiency necrosis and they may be worth closer investigation (undersides as well).
I would need to see much stronger evidence before I worried about blight
Tattieman confuses the issue by talk of early blight. Nobody now worries about Early blight which is easily controlled, does little damage, and doesn`t exhibit symptoms such as these.
Looking at the pictures it does look like there is not enough feeding for the plants to survive on and they are stressed. It does look like blackleg is there aswell which is causing the haulms to die.
Mine have a touch of early blight on them but I just remove the odd leaf and spray them.
Many thanks for your replies. Hopefully the owner will actually remove the affected plants just in case. Everything generally is growing very strongly around our whole site. There are a few problems. We are in an isolated situation and a new site so hopefully we will avoid some of the problems for a while.
I am interested in the magnesium deficiency. I have in the past had similar problems with raspberry plants and given them epsom salts. But since we are on limestone I find it surprising that we are short of magnesium.
Try and find out what went in with the sets, just well rotted manure, or manure and fetilizer
Digeroo, don`t confuse limestone with magnesium limestone (dolomite lime). Ordinary limestone doesn`t contain magnesium. However, this may be nothing at all to do with the problem. As I keep pointing out on this site, all the signs of magnesium deficiency can appear when there is plenty of magnesium in the soil, but the plant simply cannot get at it, or cannot get enough of it.
Severe weather conditions, excess of rain etc. can cause magnesium to leach out of the surface layers, heat or drought can cause it to become temporarily `locked`, and probably, most characteristic of all, a plant can grow too quickly so that even when the magnesium is there and available the plant roots simply cannot take it up in sufficient quantity. In all of these cases, when the underlying condition is rectified (usually it does this on its own as weather conditions abate, or the plant growth slows) everything returns to normal.
However, certain soils, particularly sandy ones, are poor at retaining magnesium, and it is these where remedial addition of magnesium is beneficial.
It should also be borne in mind that almost all trace elements are also poisons when they exist in excess, and they should only be applied when ithere is a genuine soil deficiency.
Problem has now been tracked down to ants. Many thanks for all help.
I have been told by another plot holder that my Mimi have blight, they don't they're just dying back.