Peter. Help!! In February I moved a 14″ diameter potted hibiscus closer to a west facing window in anticipation of moving it into the garage in April, then outside mid May. I live in southern Warren County. To keep my cat from using the soil, I put plastic bags on top of the soil. She has stayed away. During the winter there were some leaves that turned yellow. I sprayed the plant weekly for 4 weeks with Neem Oil. It helped. A few days ago I was going to water the plant. I moved the plastic bags and saw the top of the soil had clumps of white stuff with a hint of yellow. Under a very strong magnifying glass (60-100x) they seem to look like tiny cotton balls. First I thought of mealy bugs, but these were on the soil; not on the leaves. Could these white “things” be mealy bug eggs? If not, what might they be and how might I get rid of them? The hibiscus has been somewhat stressed all winter; practically no leaves on the bottom 1/3 of the plant.
It is pretty normal for a tropical hibiscus to lose leaves over the winter. Unless you have a greenhouse, it is pretty hard to do more than keep it alive over winter. It will bounce back quickly as the days get longer and, especially, warmer. The leaves often turn yellow before they fall off so that probably isn’t due to insects. I suspect the white stuff is just mold growing on the surface of the soil from being covered with plastic. Scrape it off and discard it…probably will have no adverse effect on the plant. You can start 1/4 strength feedings once every three weeks now to stimulate it into new growth for the season.