Ferns: Staghorn fern invaded by ants

I wouldn't hesitate to use Borax as a pesticide. Aside from being toxic in large amounts, it is also a good source of the essential trace element Boron, which, from what I read years ago, is frequently deficient in our local soils. I have broadcast Borax in small amounts around my fruit trees (growing in lawn grass) every few years for a long time. I can't say if it has improved yield, but it certainly hasn't hurt anything.

 

Not arguing with you for a minute @vitog but I clearly remember about 20 years ago, reading in the local paper about concerns of excess boron in farmers' fields along SW Marine Drive, Burnaby. There were theories about why that should be so and what, if anything to do about it. I was mildly worried because I bought most of my family's vegetables at one farm in particular. Funny though, I have been searching online for the past half hour and can find no reference to those reports whatsoever.

 

Mine had ants as well. I let them just hang out in the mossy dirt wood base of the plant for like two years. I ended up discovering the reason they were there. One day I flipped over a leaf and noticed it had scale. Apparently the ants like the sticky sap from the plant that the scales cause. I had to spray it with insecticide after I rubbed as much of the scale off as possible. Scale is really nasty in my opinion and I couldn’t have it spread to other plants. I keep all of my plants together in tight quarters for the winter. I haven’t seen any ants or scale since then. I kind of feel bad about killing the ants but ..... anyway I used Spectracide brand malathion. I generally only notice insects such as scale or mealybug on select plants a few months after I bring them indoors for the winter. During the summer I assume some sort of natural predator eats the mealybug or scale so I generally avoid using insecticide, and normally don’t have to during the summer outdoors. Anyway good luck