It depends on the fungus you are targeting. The best time to apply for spring dead spot is about a month before dormancy or when soil temps decline to 65°F.

 

So I've been reading here lately and see that a lot of people are talking about spraying a fungicide along with their winter pre emergent. My question is, why do the fungicide now? I thought the time for a fungus to grow was in hot humid temperatures with lots of rain/water, not in cool fall temperatures?

It depends on the fungus you are targeting. The best time to apply for spring dead spot is about a month before dormancy or when soil temps decline to 65°F.

Thanks, Ware. Would you recommend spraying if I have zeon zoysia? Not sure if that grass type is prone to dead spot or not.

 

@Lawn Noob I'm not sure how common SDS is with zoysia, but if you haven't noticed it I probably wouldn't worry about applying a preventative.

Someone with more zoysia experience may have better advice though.

 

Fall is the time of year to spray for rhizoctonia on zoysia. Zoysia patch, aka large patch, gets going in the cooler weather of fall but you see the damage it does in spring. Usual advice is two apps about 4 weeks apart. I actually had it scheduled to do for today but it was too windy, so I bumped it back to tomorrow.
http://www.walterreeves.com/lawn-care/large-patch-disease-in-zoysia/

 

Remember the old saying "an ounce of prevention is worth a pound of cure"

Spend a few bucks to prevent it now so you are not like me and fighting Grey Leaf Spot that just reared it's head last week.

 

Thanks everyone. Do you all have a recommendation on a brand of fungicide for zoysia? I've never done this before and don't really know what I should be lookin for on DoMyOwn.com

 

I would probably get Azoxystrobin (group 11) and Propiconazole (grp 3) - that's a pretty standard pairing of two different chemistry types that covers a variety of fungal diseases. You could combine them, or rotate because they both work against Rhizoctonia. But if you combine them (which you may want to do to maximize their effectiveness, and to stave off the development of resistance), you will have to come up with others from other chemical classes which are applicable to the diseases that you encounter, to rotate to. This gets expensive. Flutanil (Bayer Prostar) is another chemistry that works on Rhizoctonia, but it's over 200 dollars for a jug.

If you were only going to have 2 fungicides in your shed Azoxystrobin and Propiconazole are good standard choices. But if you really are going to have only 2, use them in rotation. Propiconazole and similar chemicals are effective against dollar spot - a disease that depending on the weather can attack a lawn practically all growing season long. Azoxystrobin has no effect on dollar spot, so save that one for the fall - spring Rhizoctonia campaign.
This is a really good resource on fungicides and diseases:
https://www.turffiles.ncsu.edu/diseases-in-turf/large-patch-in-turf/

 

@Lawn Smith, check out Rhizoctonia diseases of turfgrass and Now is the time to plan for large patch. If you prefer granular, BiaAdvanced and DiseaseEx are both widely available at big box stores and are effective at controlling large patch. If you prefer liquid, look for propiconazole and azoxystrobin to find the equivalent products.

Large Patch

Large patch occurs in the fall and spring, when warm-season turfgrasses are entering or exiting their period of winter dormancy. Infection of the lower leaf sheaths by R. solani occurs whenever the temperature of the thatch layer is between 10ºC (50ºF) and 21ºC (69.8ºF), and continuous moisture is available for at least 48 hours. Warm-season grasses are not growing vigorously during the spring and fall, and are highly susceptible to pathogen attack. Patches may also develop in the summer during periods of cool weather, especially in wet or shaded sites.

Recent evidence indicates that the majority of large patch development occurs in the fall. Symptoms are observed in the spring because plants infected the previous fall have not yet recovered. As conditions become optimal for the growth of warm-season turfgrasses in late spring/early summer, recovery occurs due to the spreading growth habit of these grasses.

Excessive moisture levels in the soil, thatch, and lower turf canopy encourage large patch development. Factors such as poor drainage, shade, restricted air movement, or excessive irrigation increase the severity of this disease.

In general, making two applications in the fall and one application in the spring with any of the following fungicides can offer effective large patch control.

 

This was my back lawn (Palisades zoysia) last October 28th. It was my 1st season with the grass and I didn't think anything of it at the time, but did I have dollar spot or brown patch? It never turned fully dormant tan all winter but had no problems coming out of dormancy this spring, so I'm not sure. I do have propiconazole, azoxy, and 3336F on hand so if I should prevent that again, I will

 

This was my back lawn (Palisades zoysia) last October 28th. It was my 1st season with the grass and I didn't think anything of it at the time, but did I have dollar spot or brown patch? It never turned fully dormant tan all winter but had no problems coming out of dormancy this spring, so I'm not sure. I do have propiconazole, azoxy, and 3336F on hand so if I should prevent that again, I will

Honestly that doesn't look like either. Large Patch provides patches typically with very distinct borders, and late October would have probably been too cool last year for DS.

 

I don't see the patch pattern of zoysia patch. Rhizoctonia patch disease looks like someone poured something out in your grass. For example:

The above patch is active, as you can tell from the reddish, orangey ring around its periphery. In spring that will all be bleached out looking.

Also, if you had rhizoctonia zoysia patch going on last fall, and it went untreated, you would have had big noticeable dead areas this spring in the same places. Big - like the picture above.

If you had rhizoctonia, you may have noticed some weird colors in the grass in certain spots in fall, and wondered about them. Then winter came and maybe you thought well that's the end of that. However, if it's rhizoctonia, the fungus actually survives and persists over winter in the thatch layer and soil under the grass that it was killing off in the fall, Thus, in spring it roars to life (or death) in the very same patches where it was seen before and resumes its spread. The grass fails to green up in that patch and the patch gets bigger. Hence the name large patch. Dollar spot can make large patches over time but it starts as tiny coin sized spots. A large infected area of dollar spot looks like several overlapping shotgun blasts whereas large patch looks like a single, large patch. It actually looks worse in spring than the fall before, because all winter it keeps killing the grass below ground. So, the fall is when you want to stop or prevent rhizoctonia. Zoysia is slow to repair the damage, so it's painful stuff. If you have rhizoctonia in the fall and treat it in the fall, you must be ready to treat it again in spring.

 

Thank you @Spammage and @Groundskeeper Willie for your analysis/explanation. So far so good this year although I know there's still plenty of time for things to go south before dormancy. I have yet to spray any fungicide although I have them on hand. I've had the H.O.C. at 2" this year, don't overdo it on the fertilizer, bag the clippings to prevent thatch build-up and only water on mornings after I mow (adjusting for rain of course). Either my cultural practices are working or I'm getting lucky.