Cabbage butterfly update

cwbdecoy Cabbage white butterflies have had a lovely time with my broccoli this year. There are several conditions that make brassicas very attractive to these pests and the brown cabbage moth. See Cabbage white butterfly.
My problem was that I inadvertently added some very alkaline compost to that area of the garden, (See recent post on Compost pH) and it is taking a while for the soil to get back to a neutral pH.

After spending a week or so removing eggs, squashing tiny caterpillars, or feeding larger ones to the chooks, I remembered a tip someone gave me long ago to deter these pests but have not needed to use before. The tip was to slip the plastic clips that seal loaves of sliced bread onto the edge of some of the Brassica leaves. White seals to deter the C W butterfly and beige ones for cabbage moth. The theory being that the adult butterflies and moths will “think” that eggs are already being laid on these plants and they look for another food source for their larvae.
My broccoli plants are looking healthier already and I have not found any more eggs under the leaves, but I don’t know if the seals are working or the pests are no longer present in our area. Has anyone else tried this tip?