Tithonia Leaves Dying, Plant Thriving

Question

I planted these tithonia plants indoors from seed and transplanted into the garden successfully. They have been flowering and are thriving, except some of the lower leaves turn yellow and brown and then completely die. They first get reddish/brown at the distal edges, then yellow further into the leaf, and then completely brown and dried up, and then fall off. I don’t know if this is a nutritional deficit, or an infection or is just the normal process of older leaves dying off.

Answer 1

This is, definitely, a fungal infection. This can happen when soils remain too wet without a chance to dry out. Saturated soils make for a good breeding grounds for fungi, and likely it has taken hold. fungicides will be necessary, and keeping the soil full of beneficial microbes will help, as well.

https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm

https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/what-are-microbes-in-soil.htm

https://www.gardeningknowhow.com/ornamental/fungus-lichen/mycorrhizal-fungi-information.htm