Emily: What are these scabs on my plant leaves?
Dear Emily: My plant has developed white scab-like things on the bottom of the leaves. What are they?
A: Scale infestations have the leaves looking like they have scabs on the leaf (could be either side). The scale can be white or brown and is actually a crawling insect that has found a happy home.
Since the insect is protected by a hard outter shell, sprays do very little good. We have tried insecticidal soap with very little success. We have had more success with a commercial insecticide. Buy one that says it is effective on scale (what else?). You can find products in most garden centers.
A better way to get rid of the scale, more environmentally friendly than insecticides and also more effective is to wipe down each leaf. Use a cotton ball or paper towel or a towel with either rubbing alcohol or Neem oil. We have actually used an old toothbrush to scrape off the scale. Be sure to hold the leave in one hand while rubbing to protect it as much as possible.
For heavy infestations you will probably have to dispose of the leaves involved.
Scale is difficult to get rid of. We tried all winter to eliminate the scale from one of our large schefflera and through constant spraying and rubbing (and some disposal of leaves) we were finally successful.
Our desert rose got infested with scale and we had to dispose off all of the leaves.
See some scale on a Sago Palm.