White cotton like substance on plant stems

This is caused by an insect called a planthopper. The nymphs are covered by a waxy material and also leave some behind on the stems of plants. Try washing it off with a hose but most likely it will return. They are unsightly but don't cause significant problems. The following is a link to information about them from our website,
https://extension.umd.edu/hgic/topics/planthoppers-flowers

Deb

Thank you for the speedy response! I'm glad to learn it is nothing ominous.