While looking thru some old pics...... (LB?)

17 years ago

While looking thru some old pics...... I found 3 varieties that appeared to maybe have Late Blight. I don't recall the plants ever dying or getting pulled though... they seamed to go on to be productive plants. After regularly spraying of course. But non of them died until hit by killing frost.

Ten Fingers of Naples:

Sara's Galapagos:

Galina's:

Is LB as devastating as we think? Is it selective, such that some plants in the same garden escape any signs of it at all, while a plant a few feet away is decimated?

Also, how could different heirlooms have different rates of LB disease in tests? Not only among other heirlooms, but among themselves in different years, like Brandywine being 48% diseased one year, and 1% diseased another year? And why aren't these #s 100% for all? I know I'll be planting the one 0% diseased every year tested!

As a side note, in tests, Bravo (chlorothalonil) was 90-98% effective in fighting Late Blight, Harpin (Messenger) was 4-7% (on potatoes), neem was 0%, and Bacillus subtilis (Serenade) was 0-7% (on potatoes.)

If efficacy = reduction in disease severity relative to unsprayed control, then the effectiveness measured, I would think, was as in eliminating or combating LB, not as a preventative as we usually think, no? You'd have to have something exist before you can try to effectively eliminate it. That makes it seem as though the % numbers above is a positive gain on LB, in other words, the treatment eliminated that percentage, whereas we are currently under the assumption that we cannot defeat it or keep plants alive once it hits. Maybe we are looking at things incorrectly?

Discuss please.

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Comments (4)

containerted
17 years ago
This is a time when you need to make a decision about staying organic or harvesting some tomatoes. I normally spray with Daconil or Garden Safe every two weeks - I alternate. But when the Late Blight alert was announced, I immediately increased to every week and after every rain. I still have some plants that are not looking as good as I would want, but they're still up and the new growth is looking okay.

Make a decision. Get some chemicals or throw in the towel. Do you want to eat or brag about your organic "attempt".

Ted
trudi_d
17 years ago
Hi Mark and Ted,

A few years back I stopped being in denial about my island climate and ordered several pounds of Serenade powder from the manufacturer. I didn't order it because it was organic, I ordered it because it was available in a large package (I think it was six pounds) and for the money it was a very cheap fungicide. I had some previous success with the ready-to-spritz bottles but I felt like I was just opening my wallet to wide too often. So I coughed up the bucks for the large package of Serenade powder.

Efficiency is priceless. So is being prepared. Because I've been spraying on a weekly basis my problems are very limited. I also am diligent about removing any yellowing leaves. I hope that everyone who grows tomatoes at home will next season start out prepared. Get the likely needed curatives/preventatives before you put the plants in the ground. Be ready with a season's supply of fungicide and use it as directed to save a lot of labor, heartache and grief.

It doesn't matter if the curative/preventative is organic or a chem product. What matters is a regular spraying program that is kept on schedule. Keep the plants tidy, keep the soil mulched to prevent splash-up. And most importantly, don't grow more plants than you can EASILY manage. Less is more. You'll be able to spend more time caring for fewer plants and have better results.

T
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carolyn137
17 years ago
Mark, challenge experiemnts have been done and the efficacies you post I don't think are too far off from such data that I've seen.

There's a reason why almost all the alerts from almost all states here in the NE have been suggesting Daconil alternating with a copper product, b'c Daconil is known to be highly preventive. No product is 100% effective, as you know.

Unless it's known that a specific disease is in the specific area where one garedens one can spray anything and conclude it worked, same as folks using eggshells and claiming that they prevent BER.

I don't think your first picture indicated LB at all and right now I forget the second picture. LOL

One of the prime sources of LB in the past has been just East of you in potato country where potato cull piles have been the source of LB. but you'd need easterly winds to get the highest exposure and where you and I live the winds are westerly.

You mentioed Bravo, but in NYS that can only be sold to commercial farmers with a pesticide license. Same for Tatoo, and both are Daconil at a higher concentration and there are some other products that also can be used only by those with pesticide licenses.

Can an LB infected plant survive the infection? To date I've had no personal experience with that but everything I've read says no, it's lethal. If you find anything to the contrary on the net, please share that with us.

Is that Gold Fleck on your Dix Doight de Naples fruits? it sure looks like it rather than being stinkbug bites.

Carolyn
korney19
Original Author
17 years ago
Glod Fleck is quite glistening in the right light, isn't it?

OK, what I was getting at was this page from Cornell:

Tools for Combating Late Blight

Obviously, some of what they think are heirlooms I don't believe are; but interesting nonetheless, that they tested a bunch of varieties for susceptibility to LB. West Virginia 63 was the best of that first bunch, at least at that time.

And in 2 different years tested, Matt's Wild Cherry had ZERO % LB while other varieties that same year tested had 15 to 100% diseased (2002) and 1 to 100% diseased (2006.)

Further down the page near the bottom, they tested various chemicals & remedies on both tomatoes & potatoes; the organic "remedies" were at or near ZERO percent effective. Bravo (chlorothalonil) was about 90-98% effective against LB.

QUESTIONS: they quote: "efficacy = reduction in disease severity relative to unsprayed control"

If something reduces disease severity 98%, does that means it "beat" LB or survived it? General idea is that it is lethal.

Is there hope to control LB for those who started spraying early as a preventative?

If chlorothalonil "reduced" disease severity, is there any hope for those trying to use it after infection?

Some questions to debate!

P.S. Why do I keep getting the signin page, keep having to hit the Preview Message button 7 times, hit back just as much, and Submit Message button so many tinmes to get the post to stick????!!!