Pests like aphids, soft scale insects, and whiteflies are all fairly common insect pests of tropical Hibiscus, though we can't identify any pests on the pictured foliage, in part due to the soap residue and not being able to see the leaf undersides clearly. Management recommendations are included on the pages linked above; they will overlap greatly, since few pesticides are registered for indoor use, and both insecticidal soap and horticultural oil smother pests on contact. If you see more of the pests, feel free to send us close-up photos in good lighting and we'll try to identify them.

Use only insecticidal soap if treating the plant (or horticultural oil), not any household soaps or detergents, as the latter may damage the plant's tissues or won't treat a pest very effectively. (Penn State has good information about why avoiding home remedies in place of registered pesticides is important; see the linked page.)

Is the sun porch heated in winter or does it get fairly chilly? They prefer not to experience temperatures below about 50-60 degrees. Yellowing leaves on indoor plants can be caused by a wide variety of factors, which can include pest outbreaks, over- or under-watering, temperature fluctuations or drafts, low ambient humidity, insufficient light, or nutrient deficiency. Since fertilization in winter should not be needed due to the low nutrient use of semi-dormant tropical plants, in this case yellowing might be triggered by chills, low humidity, and/or not enough light. The plant will do best when placed directly in front of a sunny window and/or given supplemental light with moderate-intensity grow lights. Empty any saucer used to collect drips promptly after watering, since collected water might seep back into the soil and risk drowning roots.

A weakened root system from the prior over-watering you mentioned might have caused the plant to be more sensitive to environmental stresses until it recuperates a vigorous root system. Spending the summer outside does help indoor plants recover from any stress as well as build-up some energy reserves to better tolerate the less-than-ideal conditions while inside for the season. If useful, the pages linked below have some other cultivation tips for this type of Hibiscus.

• Overwintering Tropical Plants
• Annual Hibiscus -- Clemson University Extension
• Care of Hibiscus rosa-sinensis -- Smithsonian Institution
• Hibiscus rosa-sinensis -- Missouri Botanical Garden

Miri

Thanks Miri- I did send a pic of a bug on the first photo- the close up of a leaf- if you can enlarge it you might see it- it’s almost see through. The plant has had several blooms this month and lots of buds. Hold off on half strength fertilizer or feed it to support blooming? Thanks, Barbara

The insect you mention in the first photo is blurry and we can't see enough detail. If you get a chance to take another picture, we're happy to take a look. At best, based on its overall color and shape, we can make a guess that it's a shed aphid skin, not the insect itself. Fertilizer is usually not needed for indoor plants (and overwintering tropicals) during winter because the days are too short to support much, if any, new growth, and the plant is not using-up nutrients nearly as fast as it might in summer. While a few nutrients are lost out of the potting mix via leaching every time you water, watering is also generally less frequent in winter indoors due to the soil drying more slowly, so they won't need replacement. Fertilizing when a plant doesn't need the boost in nutrients can actually benefit pests, because the nitrogen and other nutrients can support their reproduction and growth. We suggest not fertilizing the Hibiscus until it goes back outside next May.

Miri