In December, we noticed “honey dew” on the leaves and on the floor in our plant room. We thoroughly washed all the leaves with a soap, water and alcohol sotion. All the plants were then moved and spaced out through the house. We repeated this 3 times, each time a week apart. Except for 3 large Ficus benjamina, the problem disappeared. Since then we have sprayed the 3 ficus, 3 times with a horticultural oil/soap solution and 3 times with a neem oil/ soap solution, each time a week apart.. We still see honeydew on the floor but not on the leaves. It should be said that even when using a magnifying glass we have not seen any scale. So a picture won’t help. The plants look very healthy. Any suggestions?
Yes indeed, it certainly sounds like you have soft scale on your Ficus due to the presence of honeydew.
Manual removal from all the stems & leaves would be difficult due to the size of your trees but if you do see some, you can remove them with your finger or a soft children’s toothbrush. These insect pests are difficult to treat due to the cottony/waxy covering on their bodies which they use as a form of protection. They also breed & multiply rapidly when infestations are on houseplants. Spraying is probably your best option. Repeated applications over 4-6 weeks or maybe longer, spraying weekly should get them under control.
Soft Scale insects prefer shade so if you can move the trees into a bright sunny location, you may be able to slow the infestation progression. Before spraying, place trees on a covering on your floor to catch the drips (an old shower curtain is ideal) as you’ll need to spray the entire plant – stems, tops & undersides of all leaves. Spraying upwards really helps. The spray solutions you previously used, horticultural oil & insecticidal soap should be good enough to do the job but make sure you use it regularly until you see no more honeydew. Indoors, there will be many generations of scale on your plants at the same time, as they breed freely, so you need to continually treat during every stage of their life cycle in order to get rid of them.