I am a beekeeper in Nowra NSW and for the last 25 years been using Bananas to cure Chalk Brood in my hives. I have never re queened the hive after doing this even though the DPI officials say you have to. I cut a banana in half down the centre, skin and all, fold it out flat flesh upwards and place under the lid on top of the hive mat. On inspection in a couple of days, there is no banana or skin visible anywhere and a lot of dead mummies out the front entrance. On inspection of the brood, no visible chalk brood can be found. If it persists do it all again and you will eventually get rid of it.
Bill S