Every year around this time our Hackberry tree becomes infested with aphids. Although the insects are difficult to see, the honeydew they exude is not. This sticky stuff gets on everything, causing leaves and other surfaces to appear shiny. It’s really bad on our stairs/handrails right now. I frequently have to wash these areas down to keep from tracking honeydew in to the house.
Just in case you’re not familiar with the working parts of the aphid (sometimes referred to as plant lice) here is a brief description of what’s going on. First – the aphid sticks its proboscis (piercing mouth part) in to the leaf or stem of the plant. Next – they suck the sap/juice from the plant. Then – the digested material (honeydew) is forced out the cornicles (2 exhaust pipe looking things). It’s sticky, like honey, and sweet as well I imagine – but I’ve never tasted it (yuk).
Part B of the aphid story is the development of black sooty mold. This stuff is very common on a variety of plants but you’ve probably seen it most frequently on Crape Myrtles. The mold (fungi) thrives on the honeydew left behind by the aphids. Usually by the time the sooty mold shows up the aphids are long gone. Typically, sooty mold is not harmful to plants.
Also, aphids and ants have a unique symbiotic relationship. Ants often “tend” aphids like cattle – moving them around and protecting them kind of like a honeydew ranch. So in addition to sticky stairs, I also have a bunch of ants running around. I guess it’s all part of nature’s rich pageant.