No, of course they are not worms. But let me start at the beginning…
I can look at the data from this blog and see what people are searching for to find my blog (either on purpose or by happy accident). Recently I noticed a phrase like this: “worms growing out of my muscadine vine”. I found this insightful and hilarious at the same time, mainly because I have had it phrased to me like that before. No, they are not worms, but rather aerial roots.
Aerial root formation in Vitis has been documented on different grape species; however, the driving forces behind the formation of adventitious roots are not well understood. In tropical areas and greenhouse situations, aerial roots in the grape family (Vitaceae) are common. In these regions, roots that form adventitiously on aerial portions of the vine may provide an adaptive response mechanism to avoid drought or flooding or provide other unknown functions. In temperate regions, freeze injury is the most likely initiator of aerial roots, as some wounding is generally necessary to induce rooting.
The consequences of having aerial roots on the vine are unknown — the vine has been stressed, but overall it is likely that these roots are not detrimental. In fact, after a freeze event, vines that produce few to no aerial roots are either not damaged or severely damaged. Other factors such as cordon death or wilting will tell whether the vine is damaged or not. Vines that produce significant numbers of aerial roots are likely only mildly damaged and will probably recover fine.
For more information on aerial roots in grapevines, check out some of the links below on the work I have done with them.