Best Defense Against Late Blight

[PNW_D]

Here some suggestions from West Coast Seeds
http://www.westcoastseeds.com/topicdetail/topic/11/

Late Blight has been around these parts for years, but our amazing sun drenched spring/summer has certainly helped delay its onset this year ....

I was saving some of the old West Coast catalogues that showed how to set up poly tunnels to keep plants dry - but did a 'clear the clutter' thing and out they went

[bcday]

Every day more people are bringing infected branches from their tomato plants into garden centers to find out what's wrong with them or to have Late Blight confirmed by garden center staff. And of course they're spreading thousands of spores from the infected plants everywhere all along the way from their garden into the store. Yesterday nine people brought infected plant material into a store near my place.



I'm definitely keeping up with the Daconil spray!

[Robert Brenchley]

Where can we confirm the claim that the A2 type can survive in the soil? If that's true, it's a major departure from the previous strain. I think it needs to be checked out, as that would then require changes in the way the disease is managed.

We get strong winds at times as well. A neighbour of mine has a strongly built polytunnel type of structure, with a roof and no walls. That might be the way to go. If I was going to build a tomato house, I'd want something that would keep plants warm in spring, and protect them from late frosts, without getting hot in summer heatwaves. Right now I'm a bit unsure how best to go about it.

[carolyn137]

Originally Posted by Robert Brenchley

Where can we confirm the claim that the A2 type can survive in the soil? If that's true, it's a major departure from the previous strain. I think it needs to be checked out, as that would then require changes in the way the disease is managed.

We get strong winds at times as well. A neighbour of mine has a strongly built polytunnel type of structure, with a roof and no walls. That might be the way to go. If I was going to build a tomato house, I'd want something that would keep plants warm in spring, and protect them from late frosts, without getting hot in summer heatwaves. Right now I'm a bit unsure how best to go about it.

I think it was the A2 strain that was reintroduced to the US in about 1990 but I'd have to go back and do some Googling to confirm that. But since then there has been sexual mating of the vegetative form of LB and now there are many different subtypes, so much so that in some places in the US the market gardeners and larger commercial growers need to know which subtype is present b'c not all anti-fungals work against ALL subtypes.

The spores of almost ALL tomato pathogens can exist in the soil. Some. like Fusarium, can only exist where the ground doesn't freeze deeply. others, such as Verticillium can last a long time, years, in soils that do freeze deeply.

Many folks in areas outside of the current target area of New England and adjoining areas are, I think, too worried about this current threat.

In which case a call to a local Cooperative Extension office might be in order to see if there's been an increase, this year alone, in what normally is a disease that isn't that frequent, as bcday said above. The PNW has always had a high rate of Late Blight, which is one of the reasons that Drl Baggett at oregon Stae bred the variety Legend, which has just the one gene for LB tolerance.

And I know that the UK has had their share of LB as well.

[Robert Brenchley]

It's definitely the A2 strain. I did some googling around just now, and discovered that it's only the oocyte that can survive overwinter in soil. That requires two strains to be involved in a single infection. I can't speak for the US, but as far as I can discover, it's happening rarely if at all in the UK at the moment.

[amideutch]

This is how I try to beat the rain and disease and it works pretty well. Ami

[carolyn137]

Originally Posted by Robert Brenchley

It's definitely the A2 strain. I did some googling around just now, and discovered that it's only the oocyte that can survive overwinter in soil. That requires two strains to be involved in a single infection. I can't speak for the US, but as far as I can discover, it's happening rarely if at all in the UK at the moment.

http://fieldcrop.msu.edu/documents/E1802.pdf

The above link provides all the different subtypes now found in the US as single subtypes as well as those formed by sexual means.

And you're right, it's only the sexual oospores that can survive in soils, even those that freeze, for years.

And I hope that the two mating types are not in my area right now but I just don't have an answer to that. And so far, my plants don't have LB. A bit of Bacterial Speck and some Septoria Leaf Spot, but no LB, fingers crossed.

I should have done my Googling before I answered the question.