using chlorothalonil in hot weather, need quick reply

homebody_2007July 6, 2010

Hi all,

We're leaving town for a week tomorrow, and I have to decide whether to spray chlorothalonil tomorrow morning before we leave (hopefully after that plants dry, but before the temps get in the 90's) -- or whether to let the early blight really take hold.

This week's temps will be in the low to mid 90's (located in southwestern Ohio). I'm wondering if spraying them will hurt them, even though it will be hot, if I do it in the early morning.

I've had signs of early blight the last few weeks, and have put down weed block as a soil barrier, caged the plants, and trimmed off any leaves/stems with any sign of disease. I sprayed last Wednesday with Ortho Garden Disease, really getting each plant thoroughly, but still had to prune some more foliage this morning -- it was too hot to spray when I got done. I didn't have to prune them severely, I'm hoping to not pull any plants.

The new foliage looks healthy, and they're beginning to set fruit.

Thanks for any information about using chlorothalinol in hot weather!

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jtcm05(Zone 6 CT)

Read the label. That's why its there.

    Bookmark   July 6, 2010 at 2:20PM
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mustard_seeds(4 -Onalaska Wisconsin)

I think OP is looking for some advice from gardeners who have had some experience, maybe not just the label on the fungicide.

How long are you going to be gone? I would think if you applied in the cooler morning you should be okay.

Your post makes it sound like you caged only recently. I think it is best to get cages and stakes in at the time of planting so avoid disturbing the roots and help your plants have early support.

    Bookmark   July 6, 2010 at 5:13PM
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Thanks for the quick replies!

We're going to be gone until next Sunday, and temps in low to mid 90's until Friday.

I had read the label thoroughly, it didn't say much -- it did say to avoid in hot weather, but not whether early morning was okay to apply -- I called Ortho and got a person that just read the label to me, and didn't know much about growing tomatoes.

We've had so much hot weather, after lots of rainy days, that the choice becomes to either use something regardless of the heat, or watch the early blight go crazy.

Mustard Seed, I couldn't agree with you more about the caging-- trouble was, after last year's bout of early blight, I was advised to clean all the cages with a bleach solution, and it was such a hassle to do that I got around to it late. . .but paid the price in caging late & the tough job that can be. Luckily, the plants seem to have forgiven me, and are growing well (except for blight on lower leaves that I'm pruning off).

Where I really blew it was, not laying down some kind of soil barrier to avoid the splashing of the lower leaves -- I planted in a different location & thought I might not have blight. I guessed wrong ;-)

We have laid down weedblock fabric though, and it looks like we might manage a season despite the blight -- the new growth looks really good.

I did get a call back from my county extension agent after I posted this, and he also said an early morning application should be fine.

Thanks again!

    Bookmark   July 6, 2010 at 10:06PM
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i've had pretty good success spraying in
the evening around 7pm or after the sun goes down.
to be perfectly safe i would spray the diaconil
on slightly more diluted setting.
i've never lost a plant this way.
hope this helps .


    Bookmark   July 7, 2010 at 3:43PM
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Just to reinforce previous comments, I have been using chlorothalonil based products for many years in a variety of weather condx and never had a problem. Will spray tomorrow in my garden, (every 7-10 days), and it has been in the 90's and 100's even here in coastal MA all week. I always spray in early morning before bees are up and about and before the onshore breeze comes in from the bay. As an octogenarians, I don't last much longer than mid morning anyway.
Good Luck.

    Bookmark   July 7, 2010 at 9:31PM
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Hi all,

We just got back from our vacation -- we sprayed early Wed morning, using the recommended label amounts, and the plants all look great -- we had rain & high temps while we were gone and the foliage really took off.

There is one spot on a cherry tomato plant of diseased leaves I need to prune, and probably some more elsewhere, but overall, I think we're containing early blight fairly well.

Thanks all!

    Bookmark   July 12, 2010 at 10:18AM
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