blight in the soil

[svenrufus]

not strictly a wildlife gardening question, but you lot are a knowledgable bunch, so worth asking I reckon.

We have had potato blight (and tomato!) on our allotment the last couple of years, leaving large areas which may have spores of the fungus still in the soil, limiting options where to try again. Not sure it is worth it anyway, but would like some tomatoes, so intend to try once more.

Question is though, how long will spores of blight persist in the soil, how long before I can reasonably try again on the same patch where it failed in the past? If I have a fire on the ground above an affected area, does that kill spores and neutralise the ground?

Hope someone can help.
Cheers
Sven

[Garden Carpet]

Afraid I cant answer your questions Sven.. but have you thought of growing tomatoes in a grow bag?

jaki

[Meta menardi]

The biggest thing that will cause blight is climatic conditions. Choose a blight resistant variety, and hope for good weather. Search for " beaumont periods" on 't net to find more.

[svenrufus]

Hi there
Jaki - grow bags, two reasons for not using them. 1, they would require more watering rather than just leaving them to get on with it. With the best will in the world, I can't always get up to the allotment and it might be a week between visits which I don't think they would like. 2, plastic. I'm keen to do this as 'naturally' as possible, so even if it was on the cards in time etc, I think I would still not opt to do it.

Meta - (hope you don't mind me using your first name) We used blight resistant tomatoes last year, and they were resistant, but not immune. They lasted so much longer than the self seeded ones that appeared randomly over the allotment, but still succumbed, just as the fruit was considering ripening. We planted them late, so will try earlier this year and fingers crossed. You are right about the climatic aspect of it, and both years it was when we had a wet spell that it finished off any last resistance and hope.

I still wonder though how long the spores would persist in the soil as when a plot (in fact all my neighbours are the same) has blight potential, every small advantage that can be squeezed out of it to give me an edge is needed. Knowing that (for example) 4 years sees an affected area clear of spores would give me some confidence going forward. As it is, the solanacea family of foods are dropping down my planting lists, as I don't want to spend time and effort on something that is just going to wither away before I get to it.

Cheers
Sven

[Jez]

I agree with meta menardi with regards to climatic conditions. Heavy rain fall and humidity + soil conditions can cause blight. There are ways to treat blight and this maybe worth doing 1. give your soil a dosage of lime as your soil could lack nutrients in which the fungus prefers. 2. grow your tomatoes in a different position as blight will still remain in the soil, this will hopefully give your toms a better chance. 3. take with you a tub of soapy water and remove the blighted leaves, washing your hands in between every one you have plucked! A slow and laborious process but one which might give you better rewards in the end, fingers crossed.

[Cotham Marble]

Originally Posted by svenrufus

We have had potato blight (and tomato!) on our allotment the last couple of years, leaving large areas which may have spores of the fungus still in the soil, limiting options where to try again. Not sure it is worth it anyway, but would like some tomatoes, so intend to try once more.

Question is though, how long will spores of blight persist in the soil, how long before I can reasonably try again on the same patch where it failed in the past? If I have a fire on the ground above an affected area, does that kill spores and neutralise the ground? Sven

I think you are on a losing wicket. On such a small area as an allotment it's going to be near impossible to distance a rotation so as not to pick up spores from last year's crop, in effect you'd have disinfect your boots every time you went from one end of the plot to the other.

The Soil Association does I think allow use of copper based antifungicides and these can be effective though I suspect you may need to treat your whole plot initially even if you are practicing rotation. If you are not happy using copper I'd suggest you give up on solanums or at least move to biannual growing.

Burning will sterilise the soil that is imediately in contact with a fire, although as soil is quite a good insulator the heat needs to be intense to reach any depth, and heavily burnt soil is depleted of nutrients. In the days when commercial growers still heated greenhouses with coal fired steam pipes, the soil was sterilised by prolonged 'steaming'. This involved digging out the top spit from the greenhouse and depositing it by the ton on top of specially laid piping in a steralising shed and the steam ran through clamp for a week or more.

You could try 'tub growing' potatoes - using a plastic dustbin or similar, filled with sterilised soil - obtained by 'slow cooking' material from your allotment to spit in something akin to a charcoal clamp. If you were to get the burn right the wood fuel would act as a fertliser so a relatively green solution.

Jez is right to point out the need for garden hygene and one of the things I think is a source of blight problems in growing tomatoes in open ground is that fruiting in the UK is inevitably late. This means that the fruit is often not ripe until the leaves and stem are dying back - conditions which are perfect for the development of blight and its transfer to the soil.

CM

[Garden Carpet]

You could also try growing your tomatoes in tubs too... a plastic dustbin or two could yeild a nice crop.. and you could then bring them on a bit with a bit of protection.. sheilding with some sacking or some such or creating a 'greenhouse' effect of your own. If the soil is deep enough you might not have to worry too much about extra watering.

jaki

PS.. if you used a dustbin you might also be able to 'punch' in the odd hole for some herbs.. which might also protect your toms from beasties etc. Isnt Basil supposed to have some tomato protection properties?

[Kayleigh]

You need to grow something else there rotate the crop and grow nothing that is related to the potato family..

I grew potato's in pots last year they got blight too..
I was a bad year..

[Susie]

I think the only way you will get away with growing potatoes, tomatoes, etc., is to grow in pots in a greenhouse, otherwise they're DOOMED .......

I had blight on my tomatoes year before last, I haven't bothered growing them since cos it just isn't worth the hassle

[smartie]

Growing potatoes or tomatoes in pots won't insure you against blight, as it can blow in from anywhere if the conditons are right for it. For instance from a neighbouring allotment. If your neighbours are like mine, they all grow potatoes.

The best advice I've found is to grow potatoes that mature early and hope you can harvest them before the blight arrives. Outdoor tomatoes are always going to be hit and miss - we have had three excellent years (growing in pots) and then this year some of the tomatoes got blight - likely a result of the damp summer we had.

I've not been able to find anything authoritative that suggests exactly how long it could remain dormant in the soil. The nearest I could find was "more than 2 years" - I think that blight is so endemic that it's difficult to know in each case whether it arises from spores in the soil or wind-blown spores.