Howdy:0 this may sound glib, but you may want a different umbrella. I have had a number of customers with this same issue. Often it is the color or the material that attracts them. Also, they are attracted to the smallest amounts of wine and beer ( like fruit flies), so any rings or spills on the garden table can attract. Lately we have sold a lot of fake hornet nests with very good customer reaction. Evidently, the nest fools the hornets into thinking they are in someone else's territory. I use a hornet trap a little distance from where I want to spend my outdoor time and find it to work well. Never squash a hornet in a place where you don't want them. They produce a pheremone that says "come help!" and you will have more, soon, How about that? I hope you find some part of this useful:)