cultures getting black at the top

[Helmut V. B. Hirsch]

We are experiencing a problem with our cultures of Canton S wildtype 
grown on Carolina Biological Supply Instant Drosophila Food 4-24 with 
distilled water at 25 deg C 12hr light/12 hr dark at 40-60% rel 
humidity.  Vials are turning black starting at the surface extending 
down into the medium; larvae are small and immature.  Adults seem 
active.  Larvae pupate on the cotton stopper and there is a brown 
slimy appearing substance.   No new flies have been introduced into 
our cultures for many years.  Any suggestions would be much 
appreciated. Thanks

Helmut Hirsch
Biology Department
The University at Albany, SUNY
1400 Washington Avenue
Albany, NY 12222
518-442-4311 (phone)
518-442-4767 (fax)
hvh23 at cnsvax.albany.edu