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Scale Insects

Control scale populations early!

By: Sandy Feather 2009
Penn State Extension


Q. I have a large Ficus tree that I think is infested with red spiders. The problem is that I cannot see them. The tree is dripping sap on the floor, and I have seen a few spider webs. I've sprayed with insecticidal soap several times, but it does not seem to help. Is there a systemic insecticide that would eliminate them? The tree is large and beautiful, and I would hate to get rid of it, but I cannot live with this problem.

A. It is true that red spider mites are too small to be seen clearly with the naked eye, but what you are describing is most likely an infestation of scale insects. If you are seeing spiders and spider webs, they are likely feeding on the scale insects, rather than causing damage to the tree. Scale insects can be hard to detect if you are not familiar with them because they settle in one place and remain there throughout their lives, looking like brown bumps. Scale is a common problem for ficus trees.


Scale Insects and Honeydew

These pests tap into the plant's carbohydrate-rich sap, and their excrement is politely known as honeydew. Honeydew is clear, while ficus sap is milky white.

Check the leaves and branches for brown bumps, which are adults that have settled and covered themselves with a protective waxy coating. That coating makes it challenging to control them because it makes them pretty much impervious to contact insecticide applications such as insecticidal soap.

Magnolia scale on a branch
Huge scale infestation!
Scale lined-up on a Magnolia branch

Insecticides are most effective when you target immature scales. Known as crawlers because it is the only time in their lives when they are mobile, they are very susceptible to soft insecticides. You may need to use a magnifying glass to see crawlers clearly.

 

Scout your ficus weekly and apply insecticidal soap when you see them on the move. They hatch out from under the coverings of adult females. Be sure to lay a plastic tarp to protect floors, rugs and/or furniture before spraying insecticidal soap indoors, as it can stain. It will take repeated applications and patience to get this infestation under control.

You can also use a cotton swab to remove the adults from branches and leaves. Do this as gently as possible to avoid damaging the leaves. Another option is to repot the ficus, using Bayer Advanced All in One Potting Mix. This product contains fertilizer as well as Merit insecticide (imidacloprid), a systemic product that will help control adults as well as crawlers.

Magnolia scale crawlers
Early hatch stage
Scale crawlers

A combination of approaches -- repotting into insecticide-laced potting soil, removing the adults and targeted applications of insecticidal soap -- will be more effective and faster than any one of these options alone.

If you move your ficus outdoors for the summer months, be sure to scout it regularly for a fresh infestation of this pest, and take steps to get it under control before moving it back indoors for the winter.
   

MORE

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Honeysuckle aphid

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