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Fungicide Dosing Question For Today

4192 Views 14 Replies 3 Participants Last post by  Lawndad
Hey everyone,

I sprayed my whole lawn with PatchPro (Propiconzale) at 2oz/1gal on July 23rd looking to beat some BP and a little of Dollar Spot. I then made a small bath of PatchPro of the same concentrate and sprayed a few selected diseased areas yesterday (about 9 days later) and let them dry. We got a ton of rain last week so it definitely had weakened my first fungicide app. I wanted to spray a quarter of the amount of Immunox (Myclobutanil) today. The label calls for 84oz/gal of water and I would only use 32oz total on the whole lawn. I would be careful to skim over the areas that I sprayed yesterday but are there any issues with that? I know some licensed guys will mix two fungicides together in the same spray and tackle bigger problems. I would be applying them on different days and according to label instructions. My real concern and reason for the post is if the two would cross paths where I sprayed yesterday and then later today with the Immunox would that be a problem or just a better fungicide all together?

Thank. :thumbup:

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84 oz per gallon of water doesn't sound right to me at all. That's 3/4 of a gallon. It looks like the whole bottle you posted is only 16 oz, so 5 bottles per gallon?

Spraying myclobutanil after propiconazole should be fine. But please double check that rate. Since you're about 10 days after the last blanket app and there's active disease I would go for a full app rather than a quarter. You'll need to spray about every 2 weeks to keep it under control.
So I take it you have 6,000 sq ft of lawn. That's fine, but I wouldn't go too far below a gallon of carrier(water) per thousand. My advice: do another 1 oz/K of propiconazole(6 oz total) plus your 32 oz of myclobutanil mixed together in 4-6 gallons of water. Spray that over your 6,000 sq ft of lawn.

Edit : Eagle 20EW may be a much cheaper source of myclobutanil .
They should be safe. They're both DMI-triazole fungicides so there would be no point in creating a mix of the two, mixes typically consist of fungicides with different modes of action(e.g DMI+QoI ). But if that's what you have on hand no problem in using them. Maybe look into getting some chlorothalonil or azoxystrobin if you're going to be doing long term fungicide and need to alternate to a non-DMI.

Edit: yes, add the fungicides to 6 gallons of water. Make sure your sprayer is calibrated to 1 gallon per K and won't dump the 6 gallons over 2,000 sq ft or something. Add some surfactant as well(baby shampoo/dish soap/NIS).
Chlorothalonil is rated higher than propiconazole by NCSU for Brown Patch. Myclobutanil is rated worst.

Chlorothalonil is a great fungicide and it was one of the most widely used fungicides in home lawns until manufacturers decided to no longer label it for home lawn use under EPA pressure. Some of the history behind that is described here:

But you are correct, chlorothalonil is no longer labelled for home lawn use. Legally, you shouldn't use it.

You should switch your AI about every 2 apps. Switching from propiconazole to myclobutanil is not going to do any good since they're the same class of fungicide. But my suggestion would be to just mix 2 fungicides for every application. A mix of propiconazole and azoxystrobin for example is going to kick some @ss.
If Daconil was still labeled for use in home lawns, a mix of propiconazole @ 1oz/k + Daconil @ 4oz/K every 2 weeks would do a great job on BP. It does leave a white film on the grass that persists for a long time. Or so I hear :mrgreen:

If you have kids don't chance it. Stick to propiconazole @2oz/K, it's plenty good , kept my grass safe from BP all summer and fungal pressure is very high here. Fall is around the corner.
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