Hi Ya, I wonder if your kale has been ravaged by pigeons or caterpillars. They are the ones that usually do that type of damage and even under debris netting it amazes me how the cabbage white manages to get in. We suffer white fly badly as well and I have resorted to an organic spray but it knocked the fly down but they soon recovered. I have actually seen white fly wriggle though the netting. I grow all brassicas under debris netting this year and apart from white fly found it very good. I did notice that when using normal black netting there were more ladybirds on the crop and the kale seemed to be left alone as if the baddies preffered the softer options. Very annoying and frustrating but I am also at a loss of what to do. Maybe releasing some ladybird eggs under the netting would help? I may try that next year and get some from the nematode people. Any else tried them? Happy Gardening