Tiny Clear Balls on Grapevines - Explained

Concerned about finding your grape vines covered in tiny clear balls, that look like insect eggs? I was too, but it turns out, we don't need to be.

As I write this, I'm sharing my tiny office space with dozens of young grape vines, all of which I started from cuttings this winter.

The lion's share of these cuttings are of wine and grape-making varieties that I received from the wonderful Susan Rombough (widow of the esteemed grape collector and educator Lon Rombough.)

She runs their site BunchGrapes.com, and in my opinion it's the best place to order excellent grapevine cuttings from an almost unbelievable collection of varieties.

I was delighted to receive extras of every variety, and even more delighted when every one of my cuttings took root, and began to grow. And then...I noticed the eggs.

At least, I thought they were eggs. They were very small, and clear, and appeared usually in clusters (although sometimes singly) along the leaf buds, tender green shoots, and soft baby leaves of my brand new darling plants. And they seemed to show up over night!

I started smushing every one of those nasty little balls that I could find, until I actually damaged a perfect little vine in my ardor. That was when I realized I'd better slow down, and figure out if these little "insect eggs" were worth all my concern.

They seemed to only appear on certain varieties, so I told myself that perhaps a certain kind of insect had been bothering just a particular section of the vineyard these cuttings had come from. Then I looked at the young Concord grapevines I'd started from cuttings I took right here at home. They were even more covered than any of the others!

Susan's vines are in Oregon, mine are from here in Maine - yet the same phenomena was showing up on all of my Concords, and certain varieties of the cuttings from Oregon, primarily Interlaken.

The other oddity was that the balls were different sizes - surely if they were eggs they should be uniform. And the gel-like substance left on my fingers was clear after I smushed them - not cloudy or filled with any insect larva inside.

I stayed up late that night looking up everything I could about them. It turns out, these little clear balls are just tiny balls of sap know as "grape pearls", that occur on certain varieties of grapevine, when they're in a season of rapid growth.

The best information I could find came from the Iowa State Extension University and Outreach site. They state:

According to the Ontario (Canada) Ministry of Agriculture "Tender Fruit Grape Vine Newsletter for Commercial Fruit Growers" (Volume 11, Issue 5 May/June 2007) these are sap droplets called grape pearls or sap balls.

Iowa State Extension University and Outreach

Here's one more key excerpt from the same site, in which they quote a specialist from the Ontario Ministry of Agriculture, Food and Rural Affairs:

Grape pearls are small sap-like, fluid-filled balls that are exuded from surface cells of rapidly growing grape vines.
~ Neil Carter, Grape IPM Specialist with OMAFRA

Interestingly, it seems from at least anecdotal evidence that grape pearls are a phenomena that happens with American type grapes, but not French or most hybrid wine-type vines. I found this played out right here in my office when these tiny clear balls covered my little Concord and Interlaken vines, but not the French Hybrid variety Marechal Foch, which is crowded closely into the same space with them.

If you've been fervently crushing tiny clear balls on your grapevines, in fear they're something insidious, I hope this helps set your mind at ease! I'm delighted to now watch these curious little balls forming, knowing they represent the rapid growth of my healthy little grape vines.

Do you have other homestead grape growing questions? Let's learn together! Feel free to leave questions in the comments and we'll try to find the answers. Happy growing!

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