"If you turn to a veterinarian to help treat this crop issue, most likely they are going to prescribe Nystatin for this yeast/fungal infection. The problem with Nystatin is that it must come into contact with the Crop and yeast/fungal infection at all times or it renders itself useless. And because the bird needs to eat and drink during the treatment, I have never found Nystatin to be useful one bit. If you can get your vet to prescribe you Clotrimazole, then do it! This stuff is very powerful and will knock out the most powerful yeast infection a bird can have. If is often given to human babies with Thrush of the mouth with great success. However if you don't have an avian vet or they do not have this medication, you can turn to vaginal cream. Yes, sounds bizarre, but I was directed by an avian vet to use this on my Chronically Slow and Sour Crop patient. And it wasn't until I started with the vaginal cream was I able to save my bird. Monistat. (Miconazole Nitrate) or Gyne-Lotrimin contains Clotrimazole. The other ingredients are glycerin and other inert products. You can use the Generic form of this product as well. I use the 2% formula. You will need an empty syringe with no needle. Stick the tip of the syringe into the tube of vaginal cream, withdraw the plunger and squeeze the tube and suck up 1cc. You are going to give her 1cc, 3 times a day. So 1cc [in the morning], 1cc at noon and 1cc at roosting time. Again, squeeze it onto the tongue with the birds head level. . .
I have also had GREAT luck with Acidified Copper Sulfate in the water for 5 to 7 days. Always use the Acidified stuff you get from a poultry supply, never use anything not poultry approved. This is guaranteed to clear up the most wicked yeast infection. However just keep in mind, if something like the feed is causing this yeast infection or she has an internal infection, an internal fungal infection, Crop worms, she is Egg Bound, intestinal worms or something else is causing this Crop to be slow and sour, you will need to correct these first before you can cure your bird of this yeast infection. Once you can go two mornings with nothing in the Crop, you can assume you have cured the bird of this issue. She can then go back to her regularly scheduled day. Keep her on probiotics for one week after treatment."