I have an indoor schefflera with scale insects. I have cleaned them off with...
I have an indoor schefflera with scale insects. I have cleaned them off with paper towel soaked in insect soap. They are recurring. Questions: any better treatment? If I knock them off on floor or into soil of pot, will they die or can they come back? Do they have a flying stage? The schefflera is 4-6 feet away from other plants; are those in danger? Many of the leaves I have treated now have a whitish dust entirely covering them; is this residue of the insect soap or some sort of other problem? Can I strengthen the schefflera so it is able to resist? I recently repotted. The last time I wrote you did not respond, but 8 days later emailed for a survey, so I saw your response then. Hope this time goes better. Thank you.
We just received your question over the weekend and were not in the office for MLK Day.
Scale insects can be difficult to manage and there are different types. There are products on the market for scales such as insecticidal soaps or oils that are relatively "safe". Please follow the label directions for whatever product you choose. These products should be directed to the crawler stage (these are a very small, young stage that are mobile on the plant that occurs after egg hatch.) This life stage is most susceptible to control.
You can test to see if the scales you see on the leaves are still alive. Often the scales can remain on the plant long after they are dead, making the infestation look like it continues to occur. You can squish the scale on the leaves, liquid will come from the scale if still alive. You may want to use a hand lens to monitor.
If you are able to remove the scale insects, dispose of them. Do not let them fall into the pot. If you are knocking off the scale insect in the crawler stage, they may be mobile and are able to crawl. They do not have a flying stage. You should isolate the plant from other plants as the scale can be susceptible to other plants. If the plant is highly infested, it is best if the plant is disposed of. See our website for more information on scale insects http://extension.umd.edu/hgic/scale-insects-houseplants
Not sure what the white residue is on the leaves. You can send us digital photos so we can see what you are referring to.
To keep your plant healthy focus on proper care. Look at the link from Clemson for more information http://www.clemson.edu/extension/hgic/plants/indoor/foliage/hgic1511.html
Thank you for your response! I have a couple more questions--the infected Schleffera (it's tall, maybe 9' high) is 4 or 5 feet distant from any other plants. Is this sufficient distance to prevent transmission? Also: if I contact the scale insect with alcohol when removing it, does this kill it on contact, or only help dislodge it? Does treatment with soap or oil actually kill the insect on contact, or must it be applied thickly enough to smother it? I don't know how the plant acquired these critters; it is next to a window which is open in summer, and something has eaten caterpillar-like holes in 2 or 3 leaves near the window and there was honeydew on those leaves (no honeydew to speak of on the others). Thank you!
4-5 feet may not be far enough. We'd recommend more like 8-10 or another room altogether.
Yes, the alcohol kills the insect. Soap and oil do not technically 'smother' the insect by the depth of the application, but it must be thorough in order to be effective. It does not poison the insect with a toxin.
Yes, scale insects can come in from outdoors but a more common mode of transmission is from the nursery or a newly introduced houseplant.
Thanks! This is actually a conversation! No new houseplants, but I recently repotted the Schefflera in a newly-puchased bag of potting soil. Might they have been in that? Haven't seen any on the other plant I repotted with that soil, but I'll start watching. --So if I touch a scale insect with an alcohol-laden Q-Tip, I can figure it's dead now, and I don't have to worry about removing it or where it falls?
Doubtful it came in the potting soil.
As long as the insect gets a good dose, it should die. However, to be safe, we'd suggest you sweep/wipe up any that fall and dispose of them in the trash.