I was one of the original testers of GardenShield when they first put it on the market. I can't say one way or another whether it's effective at deterring borers because I only applied it once. That one application, although applied exactly as directed on an overcast day, caused horrible spotting on my iris leaves, so I refused to reapply it as the directions recommend. It will wash off in rain or overhead watering, so it needs to be reapplied repeatedly in order to maintain whatever effectiveness it may have. Because of the reapplication requirements, it is an extremely expensive product with which to attempt to control borers. And it makes the plants look miserable with all the spotting.

Thanks for the info laurief. I think I will stick with the old method---squishing them in the leaves. Marg