dome tent

I'm trying something new in the garden. This is a dome made of PVC pipe and covered with tulle. It is suggested in the Square Foot Gardening book. Every year I try to grow broccoli and cabbage and these lovely little white moths fly around and alight on the leaves and next thing I know there are holes in the leaves. The PVC pipe is just to hold the tulle up off the plants, while still allowing air/water/sunlight. Will it work? Ask me again at the end of the season. Every year I try new gardening ideas and every year at least half of them will NOT be tried again.