Are fungicides generally okay to apply in high heat?

yes

are fungicides generally a low stressor on the grass?

correct. you are thinking of herbicides. you are fine

 

Generally low stress except for the DMI fungicides like Propiconazole. They can cause turf damage when used in high heat. It is most described for bentrgrass and seems to be less of an issue on Bluegrass and Fescue, but is still something to be aware of.

 

Generally low stress except for the DMI fungicides like Propiconazole. They can cause turf damage when used in high heat. It is most described for bentrgrass and seems to be less of an issue on Bluegrass and Fescue, but is still something to be aware of.

Currative rate actually made my grass pop. It is in the mid 80's here... :lol:

 

@Babameca You Canadians are :crazy: 80's isn't hot....

I have seen issues with Propiconazole, but not below 90 degrees. Even if it gets to be 95 degrees, though, the lawn won't catch on fire or die with a DMI, but you may get some yellowing. The other problem with the DMIs and heat is that they stay in the leaf tissue for weeks so you can get damage 1-2 weeks after application if it gets hot. For preventive in summer here ,where it can be 90 degrees or hotter for weeks at a time, I tend toward other options, but if I have something going on in the heat and a DMI is the best option, I will use it.

Velista has served me well this year in the heat and seems to provide longer protection. I have not found Propiconazole to last more than 3 weeks, even at the high application rate. Velista seems to give a good 4 weeks of protection. That could just be luck or chance and not a real difference, but combined with the temperature issues it makes the choice easy for me.

 

@bernstem Actually this is the hottest (duration wise) summer I have seen. We hit 98 in May beating all time record by 10F. Then had mid 90's for a week in June and another low 90's are on the horizon. I applied between the 2 hot waves and immedietly watered in. My clippings rate was identical upon my last mow. Maybe it takes more time...

 

@Babameca It is dose and temperature dependent. Night time temperatures also matter. Bluegrass and Tall Fescue are less prone than Bentgrass where it has been most described.

Over 95F (37C) is hot even here, though it will usually hit that for at least a week or so most years. If it gets above 100F (38C), I take notice.

 

In May, my lawn company applied a liquid fungicide. I have Fescue. Then a month later I applied a granular fungicide (disease X)as the fungus was still there. My yard is now very yellow and I wonder if I put too much fungicide on. Temps have been in the high 80's to low 90's. Is there anything I can do to reverse the damage?

 

In May, my lawn company applied a liquid fungicide. I have Fescue. Then a month later I applied a granular fungicide (disease X)as the fungus was still there. My yard is now very yellow and I wonder if I put too much fungicide on. Temps have been in the high 80's to low 90's. Is there anything I can do to reverse the damage?

Can you post some photos of your lawn, distance and up close? You might want to review the fungus ID thread and the fungicide guide in this forum.

https://thelawnforum.com/viewtopic.php?f=9&t=4167&hilit=fungicide+guide

https://thelawnforum.com/viewtopic.php?f=9&t=4042&hilit=fungicide+guide