Grapevine Growth

Asked July 12, 2014, 2:38 AM EDT

Do you know what this is? I have been growing grapes for several years and I have not seen this before. I found 2 of these on my vines. Is it harmful to the vines? Thanks

Washtenaw County Michigan grapes viticulture

1 Response

The strange growths are galls caused by the presence of tiny insect larvae living inside the tissues of the grape shoot. I cannot recall right now whether this one is caused by a fly or a wasp species. These are uncommon, and rarely numerous enough to cause a real problem for a grapevine.