Large Patch Lawn Fungus

For those of you with St Augustine grass and zoysia, large patch fungus is starting to rage through lawns. In the early stages it will have an orange cast to it, sometimes pink. The patches will be irregular in the lawn as it typically follows the flow of water.

Here’s the thing: I DO NOT recommend you apply fungicides. In fact, applying fungicides to a lawn this time of year can actually make the recovery slower.

Think about this: Your lawn is already growing slowly. You are probably only mowing every 7-10 days. That’ is because our lawns need a lot of sunlight to grow and we don’t have that right no. The days are short and getting shorter. The cooler temps also slow it down and if you are further north, it’s even slower from the blast of cold that came through the last couple weeks.

Fungicides that you apply to help stop large patch fungus are growth regulators. That’s how they work. They slow down the spread of the fungus by regulating it’s growth rate. This also will have an effect on your turf and slows it down in the process.

So think about it: you see those brown patches in the lawn that are large patch fungus. Brown areas don’t just magically turn green again - instead the rhizomes or stolons (How Southern Grass Types Grow) have to push up fresh grass blades to replace the dead ones. The grass is already slowly growing from weather conditions and now you are going to slow it down even more with fungicides. That means the brown spots will just stay there even longer.

Instead, you should continue to fertilize your lawn with nitrogen to help it to grow faster. It’s not going to grow too fast because the cold and short days are keeping it slow but by fueling it with nitrogen, you can help it to repair itself (regrow) faster. If you apply fungicide, this will not happen.

So again, do not apply fungicides in fall and winter. Apply nitrogen instead. If the lawn is not dormant, then hit it with Flagship every 30 days. Also continue to hit it with RGS (root growth stimulant) which will also help it to regrow. If the lawn goes fully dormant, then stop and start back up again in spring.

I know this is counter-intuitive because you hear people in FaceBook groups say “stop feeding your lawn when you have fungus because that will make it worse” but context is important. That advice is mostly applied to summer fungus (when the lawn is growing fast) and the people that you see touting that strategy are not from Florida in the first place. Florida is very different in the way we approach lawn care because in the southern part of the state, we never go dormant.

Now you could also do nothing. Just let it be. Again, the spring time will regrow everything and there will be no long term damage.

I hope this helps. Please feel free to join our Florida Lawn Care Nuts Facebook group if you want to share pictures and understand what others are doing across the state this winter.

Al