Is this heat stress or a fungus?

[micvog]

The past week has been in the low-90s with a 0.5" rainstorm. The lawn had some drought-stress near the end of the week, much of which has disappeared with another 0.5" of rain last night. However, there is a suspicious spot that looks like a fungus to me, but it doesn't match up exactly with the diseases I looked up at the MSU Turf Disease website (leaf spot is my best guess).







I have been aggressive with the N this Spring as I try to get the lawn established.

I ran a little late on the preventative program - cracked corn (20#/K) went down on 5/26, and Serenade went down (3oz/K) on 5/27 and 6/4. We are expecting some more rain this evening, and I plan on putting Serenade down tomorrow. I was thinking of SPOT spraying Bayer Advanced Fungus Control for Lawns since it is available locally (AI is Propiconazole).

This spot is one of the first to show heat/drought stress.

Any comments or thoughts appreciated!

[Jackpine]

It's not an exact match but enough so that I would hit it with the Propiconazole at the heavy rate. Cooler weather and more rain coming could very well make it worse.

[Pway]

It's not an exact match but enough so that I would hit it with the Propiconazole at the heavy rate. Cooler weather and more rain coming could very well make it worse.

I have some areas that look like this. I sprayed last week with propaconozol as Jackpine suggested. I'm not sure I notice an improvement yet but expected 2 or 3 subsequent sprays to be needed. If that doesn't work I'll try azoxystrobin and see what happens. Might be due for some more N too but big rain coming so that won't happen until later this week at the earliest.

[Green]

Even if your fungicide works against the disease, it's not going to look better until it grows out. And Propiconazole reduces growth rate (like a PGR), so you won't see that happen immediately.

[Jackpine]

It's not an exact match but enough so that I would hit it with the Propiconazole at the heavy rate. Cooler weather and more rain coming could very well make it worse.

I have some areas that look like this. I sprayed last week with propaconozol as Jackpine suggested. I'm not sure I notice an improvement yet but expected 2 or 3 subsequent sprays to be needed. If that doesn't work I'll try azoxystrobin and see what happens. Might be due for some more N too but big rain coming so that won't happen until later this week at the earliest.

I mixed some Daconil (low rate) in and one treatment did the trick. Didn't noticeably affect the growth rate however, it's in full growth mode so probably not as noticeable at this point. 10 days since the Prop/Dac went down and applied PGR today so will see how that combo turns out. LOL

[bernstem]

Daconil does not have a significant growth regulatory effect, unlike Propiconazole. I would be surprised if you saw an effect on growth rate.

[PSU4ME]

Does this stuff go away once you get into the summer or do you need to treat it?

[Jackpine]

Daconil does not have a significant growth regulatory effect, unlike Propiconazole. I would be surprised if you saw an effect on growth rate.

Sorry I must not have made that clear. I tank mixed Daconil with the Propicanazole because of the leaf spots affecting about 1/3 of the grass blades had me worried. There was no noticeable effect on the growth rate and the grass recovered and outgrew the problem in short order. Whether or not there will be additive effect due to the Prop and PGR apps remains to be seen. Even if there is I don't have enough experience using either to make a judgement.

[GaryCinChicago]

This spot is one of the first to show heat/drought stress.

Any comments or thoughts appreciated!

Heat / drought stress causes wilt, not black spores on blades.

[micvog]

Thanks Gary! I should have figured that out.

It seems to be improving so, for now, I went with an app of Serenade. If it starts to look worse, I will spot-spray with Propiconazole.