Index > Garden Blog

Date: 19 Jul 2020, Entry id: 1595135465-1

Sugar grains on leaves?

by Mark Hooten, the Garden Doc

Q: On my Stemmadenia tree I noticed tiny drops (like white sand grain or sugar crystals) and wonder if this is a disease or some kind of insect and what can I do about it?

A: Sometimes certain vigorously growing (mostly tropical) plants develop suspiciously-looking tiny "growths" mostly on the undersides of their leaves. Without strong magnification, they can be easily mistaken for mealy bugs, scale insects, or any number of parasitic disease vectors.
However, according to plant pathologists, these are actually harmless excretions actually exuded by the plants themselves. A chemical analysis of these tiny granules shows that they are nothing more than polysaccharides. Polysaccharides are basically complex chains of sugar/glucose molecules which are simply a production of all plants undergoing photosynthesis. Polysaccharides are at the beginning of the entire food-chain. These odd tiny sugar-grained nodules are actually only semi-crystalline complex sugars which certain plants have over manufactured and have had no choice but to excrete through their stomata (breathing pores).
I have personally observed Cecropia, Psychotria, Spondias (Hog Plum), and Guavas doing this... there are many others. Nothing to worry about, they are harmless, but if they bother you - wash them off with a hose water.