Late Blight Resistant Tomatoes

[feldon30]

And Early Blight can be staved off for months in even the most ridiculously wet climates.

• The soil should be very loose and well-draining.
• Raised beds are strongly suggested in wet climates with heavy clay soils.
• 4-6 inches of mulch (pine bark, pine straw, straw, etc.) should be arranged around the plants.
• Good cultivation practices should be used such as not handling the plants while wet, using bottom watering (soaker hoses), and not watering the plants in the evening.
• And depending on your political beliefs about such things, either Daconil or Serenade should be used on 5-7 day cycles from the day of planting out.

I really see no need for Early Blight tolerant/resistant tomato varieties. Daconil is also effective on Alternaria, Septoria, and Anthracnose.

I have not encountered Late Blight nor do I know what methods can be used to keep it at bay except the ones I've given above.

[carolyn137]

Morgan, all NEW foliage infection pathogens are airborne and there's no way to prevent them from landing on the leaves. And that's a problem that I think can only be approached by using appropriate spraying.

As for prevention of P. infestans, Late Blight, there are some products available to commercial farmers but not to the public. A few years back when there was a Late BLight outbreak in the Albany area, just an hour south of me, NYS had to approve use of I think it was Tatoo in the state.

So for home growers Daconil seems to be the only product that has shown minimal marginal activity and so that's that.

[velikipop]

Morgan, I follow all of what you prescribe yet I still get foliar disease. As Carolyn says the pathogens are airborne and cannot be entirely defeated. In particular since i do most of all of my growing in a community garden the chances of getting some sort of disease is unavoidable. As soon as one plot gets blight you can bet it will spread.

I have used copper spray with mixed results (not enough of cycles of spraying and years of growing to know whether it really works). I am reluctant to use it often because of its toxicity to soil and earthworms. I tried Seranade for the first time in August, perhaps late, and really did not see any appreciable difference. Next year I will try Daconil and it has nothing to do with my politics.

Carolyn, I have consulted almost all the available source to try to identify what my plants are suffering from and can't really be sure because they seem to have a little bit of
everything. The best I can do is describe what my tomatoes look like when they are infected.

It always appears on green fruit and it is a smooth dark spot that spreads but does not envelope the entire fruit. It is nothing like what is described as early or late blight. The spot will spread but uneffected parts of the fruit will ripen at the same time. Eventually the black spot will turn soft and mushy. Other fruit on the same plant will not be affected. Any idea what this might be?

Thanks
Alex

[feldon30]

I hope that early and frequent use of Daconil will give you a good crop.

[barkeater]

I've found Daconil is great against Septoria and Botrytis, and pretty good against Early Blight. Mancozeb is great against Early Blight, and only fair against Septoria and Botrytis.

I find most years I can spray Daconil on a 2 week schedule.

[maryinoregon]

Thanks for the interesting discussion. I experienced Late Blight more when I was a new gardener and did not know what to do. I have to slap myself so I won't plant out too early. That seems to help avoid it. At least for me.

I also go by Morgan's suggestions, except I don't have much mulch on the ground right now and have never used daconil. I may have a little problem with Early blight sometimes, or backsplash. Most of my plants look better than I deserve.

Mornings are getting cooler. Only a matter of time before we get fog or mist and that dew on the plants. I'm hoping for a little more time for ripening. This month has been definitely cooler than normal.

[orflo]

There is no stopping late blight (early blight is indeed called alternaria, but it occurs very seldom over here) with mulching or ...Copper is indeed a solution, but you get the metal build-up in the soil, vineyards in France were treated a lot with copper and they have a huge percentage of copper in the ground. I used to mulch with straw, but I don't do that any more, wet straw and hay are a survival medium for the spores of the ph. infestans, late blight. I tried a 'living' mulch this year (Newzealand Spinach), it makes it impossible for the spores to get down to the wet ground or straw, the spores can't germinate and the disease isn't spread any more. But this year was awfully wet, so the air was 'full' with spores of the late blight, no stopping this without chemicals. And late Blight dies when the temperatures reach over 35 degrees Celsius, but this in the north?The best way to grow tomatoes is a cover over the head, make sure the leaves don't get wet, if the leaves are wet for 14 hours, spores of the late blight can germinate. And we have the morning dew, which means the plants are wet every morning, in combination with grey and sometimes rainy weather, 14 hours of wetness is nothing.
Frank

[flying mater]

I found this on a BC agriculture page. I can look it up again if you want the link.

Q What can I do to control late blight on my tomatoes?

A

1. Grow tomatoes in a warm, dry, sunny area. If you have had blight previously, move to a different area if possible, or replace the upper soil layer since "oospores" will carryover in soil.
2. Water only underneath the plants, not the leaves or fruit. Drip irrigation is preferable to watering with a hose, to reduce water splash. Don’t overfertilize or overwater.
3. Grow on a light sandy soil if possible or cover soil with a white plastic mulch to increase soil and air temperatures around the plants and reduce humidity.
4. Growing plants under an overhang or a clear plastic shelter will help prevent spores from being deposited on plants by wind and rain. But plants must be covered before infection has occured. Covering the plants after they are infected may raise humidity and make the disease worse.
5. Grow the tomatoes on raised beds with well-spaced trellises or in containers off the ground. Tomatoes grown on balconies or roof-tops rarely develop late blight, probably because the environment is warmer and drier.
6. Remove all of last year’s tomato or potato debris to prevent carry over of disease.
7. Remove diseased leaves or shoots immediately and all plants that are severely diseased. Bury them, or seal them in a plastic bag and take to a landfill. Do not compost diseased plants. If "oospores" are present, they will survive in compost.
8. Destroy any volunteer potato or tomato plants in the garden.
9. Destroy any nightshade weeds along fencerows. Nightshade is related to tomato and potato and is also a good host for late blight.
10. Apply copper sprays or other home garden fungicides recommended for late blight at least once a week when weather is favourable for disease. READ THE LABEL. Copper, which is accepted by most organic producers, should be applied for prevention more than cure, that is, before the disease has become established.

[dice]

I don't really know if it is specifically late-blight
tolerant, but Peron hung in there pretty well for
me, better than most.

Flavor was unremarkable, though. Big plant,
sturdy stems, good-sized slicers, all bigger than
a baseball.

[cecilsgarden1958]

Interesting read!

How about early blight? Any varierties known to tolerate it better then others?

CECIL

[feldon30]

With preventative maintenance, even in the wettest climates, Early Blight should not be an issue. Houston is pretty wet.

[dice]

I did not see West Virginia '63 mentioned in
this discussion. Anyone have experience with
it?

http://www.wvu.edu/~agexten/sustanag...c/Moreon63.pdf

[cecilsgarden1958]

Originally Posted by dice

I did not see West Virginia '63 mentioned in
this discussion. Anyone have experience with
it?

http://www.wvu.edu/~agexten/sustanag...c/Moreon63.pdf

I grew WV63 this season and although, I don't have a problem with late blight, early blight got a hold and really tore into the garden. WV63 was perhaps the healthiest plant in my garden and I don't even recall any early blight symptoms on it.

CECIL

[dice]

Here is another one to try, Ukrainian Heart
(if someone knows that this is *not* late
blight tolerant, feel free to say so):

http://vegvariety.cce.cornell.edu/ma...il.php?ID=2568

[carolyn137]

Originally Posted by dice

Here is another one to try, Ukrainian Heart
(if someone knows that this is *not* late
blight tolerant, feel free to say so):

http://vegvariety.cce.cornell.edu/ma...il.php?ID=2568

The variety in question is Ukrainian Heart ( TNMUJ) that was sent to me by Jerry Murphy of TN, is in my book and is carried at Sandhill as the link shows b'c Glenn requested all the varieties in my book.

Kathy in Tompkins CO says it did well with Late Blight, but most folks do not know how to distinguish between Early and Late Blight, both can appear either early or late in the season, so I'd take that comment with a grain of salt.

I've grown it many times and like most of what I grow it's susceptible to Early Blight ( A. solani), and here where I live, a few hundred miles to the west of Kathy in Tompkins County, I've never experienced Late Blight ( P. infestans)

There have been pockets of it here and there, but unless Kathy knows her blights, as it were, in seems a bit problematic to me. Occasionally there have been outbreaks of Late Blight in W NYS, origin from potato cull piles, and she refers to the year 2004 and I can't remember about that specific year. Tompkins County ( home of my alma mater Cornell) is also below the area where potatoes are grown, that is to the south, and prevailing winds in her area are from the West.

Perhaps you might wish to try it yourself under known pressures of P. infestans to see if indeed it might do OK, but to date I've not read or heard about a heart shaped variety with tolerance to P.infestans.