Water Droplets on Grape Leaves May Be Pearls

Small water droplets can sometimes be found on well watered grapevines early in the season. These are not insect eggs but "grape pearls" as they are called.

Q. Early in the growing season I saw small clear droplets on my grapevines. Would you happen to know what is the source of these drops?  I have had leafhopper issues in the past and I was concerned they might be insect eggs.

Grapes early in the season can develop small balls of water droplets on the leaves and stems called grape pearls. They may resemble insect eggs but they are not and can be ignored.

A. Not too many people see what you saw. We are too busy to notice. These droplets are tiny and difficult to see. Not all kinds of grapes seem to have them. You might see them on Concord or Thompson seedless. Nothing to worry about but it is an interesting phenomenon.

            They are called “grape pearls” or “sap balls” and not related to insects or diseases. However, they do look like insect or mite eggs.  Leafhopper females lay their eggs inside the leaf veins so there are no eggs of this insect to see on the underside of leaves.

Leafhoppers are tiny jumping insects found on many plants including grapes. When they feed on the leaves, the leaves develop a yellow mottled look and black spots are left behind from their feeding with heavy infestations. At this point there is nothing much to control and except for hard pesticides.

            These droplets are pushed outside the leaf when the vine is full of water and experiencing rapid new growth. They are usually found on the undersides of leaves or on young stems. It reminds me of the water droplets pushed out of turfgrass through hydathodes in the spring during cool weather. There is so much water present on grass leaf blades that golf course superintendents would send someone out with a bamboo pole to “whip the greens” and remove the “dew” on the grass.

            Don’t be concerned and ignore them. If your grapevines are dense, shake the vines so water drops to the ground. Otherwise they will dry normally and disappear as the daytime air gets hotter and drier.