Lantana disease

Question

I have Lantana planted in a large pot on my front porch, which gets a lot a afternoon sun. I water it twice a week with a gallon of water each time.

It has developed dark brown/black areas (not spots) on the leaves, which are starting to curl up and crumble/decay.
Some of the leaves have been eaten away.
I do see a lot of small (almost microscopic) gnats or flies over and inside the plant.
What do you think is going on here, and what do I do to get rid of it?
Thanks !

Answer 1

I suspect ‘Botrytis Blight’, a fungal disease that can be caused by too wet conditions, especially overhead watering that wets the foliage.

https://www.gardeningknowhow.com/ornamental/flowers/lantana/diseases-affecting-lantana.htm

If you think that could be what’s happening, then the primary therapy would be to change that practice and water appropriately for lantana, not too much, and not wet conditions on the foliage. The use of a soil moisture meter can help to take the guess work out of how much and when to water the soil in the pot.
Snip or pick off the most severely affected leaves. The damaged leaves won’t clear up and become healthy, but your goal should be to suppress the advance of the disease and prevent further infection of new growth.