Boston ferns

Question

The fonds are all sappy & sticky. Why?

Answer 1

This is likely Honeydew, from a pest infestation.
Treat the plant with Neem Oil.

Here are some links with more information.

https://www.gardeningknowhow.com/garden-how-to/info/what-is-honeydew.htm
https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm