protecting against mites

Kathy Matthews matthewk at FLY.BIO.INDIANA.EDU
Mon Oct 16 19:17:31 EST 1995

I've had several inquiries lately about how the stock center
protects against mite infestation of our stocks.  In case others
are interested I'm repeating this information here (for other
basic fly handling techniques a la Bloomington, see Methods in
Cell Biology, Vol. 44, Drosophila melanogaster: Practical Uses in
Cell and Molecular Biology, pp. 14-31).  We don't use miteicides
such as tedion in the stock center.  We rely primarily on
prevention of infestation through careful quarantine procedures
of all new stocks and routine use of benzyl benzoate as a mite
repellent.  When mites are encountered we have found rapid
transfer to be a completely effective means of eliminating them
from a culture.  

* Mite cloths

      --> Make the mite cloths referred to below by wetting pieces
of cheesecloth (sized to fit your trays) with a 10% solution of
benzyl benzoate in 95% ethanol.  Benzyl benzoate does not kill
mites, but it repels them.  Mite cloths serve both to keep mites
from entering general stocks and crosses, and to keep them from
exiting infected cultures in quarantine.  Cut cheesecloth to
size, put the pieces in a glass or metal tray, soak the stack of
cloth with the 10% benzyl benzoate solution, and leave in a fume
hood overnight to dry.  

      --> WARNING: benzyl benzoate in small quantities is
considered safe for humans (see the Merck Index for a list of
things you never knew benzyl benzoate was used for), but it
dissolves certain plastics and inks.  Do not put mite cloths into
plastic trays or in contact with plastic vials without first
testing them (the cloth will fuse with a susceptible plastic in
24 hours).  Direct contact of treated cloths with ink-on-paper
will cause the writing to bleed.  Pencil on paper remains

* Routine procedures

      -->  Keep stock transfer areas clean.  Wipe down bench tops,
pounding pads, and any other fly tools with 70% ethanol daily.  
      -->  Line the bottom of stock trays with mite cloths. 
Replace the cloths with fresh ones every 6 months.
      -->  Quarantine ALL incoming stocks.

* Quarantine procedure.

      --> Carefully inspect each vial for mites before removing
the plug for the first time.  Check around the plug, around any
pupae or pupal cases on the wall of the vial (the most likely
hang out for mites if only a few are present), and on the surface
of the food.  
      --> If no mites are visible transfer some adult flies to a
fresh vial and plug tightly with cotton.  If the original vial
has a rayon or foam plug, discard it (freeze or autoclave if
waste disposal is such that mite eggs on the discarded plug might
have a chance to hatch and establish a population in your trash
can).  Keep both vials in a quarantine tray.  Inspect the
original vial for mites no less than once per week for the next
three weeks (you can expand the culture with each mite check if
you see no sign of mites).  I mite check all subcultures before
adding them to the stock collection, but I have never found a
mite-infested subculture when the original vial remained mite-
free through the quarantine period.  
      --> If mites are present open the vial over a portable
surface (such as the bottom of a tray) wet with 70% ethanol,
transfer a few adults to a fresh vial, plug tightly with cotton,
replug the original vial and autoclave or freeze it.  Any mites
that fall off the plug into the ethanol should be killed, but
wash the surface thoroughly when you are done, to be sure no
viable mites escape the transfer.  If your quarantine tray cannot
be well separated from other fly work, wrap the vial in a mite
cloth (if your vials are plastic provide a washable or disposable
barrier between the plastic and cloth).  Every 24 to 48 hours
transfer the adults to a fresh vial with a tight plug, discarding
the older vial, until you have made 3 to 5 transfers (if the
flies are producing enough eggs go to 5).  Proceed with
quarantine as described above for uninfested stocks.  

* Living with mites.

If you are in a building where mites are endemic use tight cotton
plugs instead of rayon or foam for all stocks, not just those in
quarantine, and cover bottles and vials with mite cloths as well
as lining the bottom of trays with them.  Wiping your bench top
with 10% benzyl benzoate may offer some added protection from
wanderers.  Change your stocks regularly (30 days at 25C should
be an upper limit) and spot check for mites so that problems are
caught early.
Kathy Matthews			Bloomington Drosophila Stock Center
Department of Biology		MATTHEWK at FLY.BIO.INDIANA.EDU
Indiana University              MATTHEWK at INDIANA.EDU    
Bloomington, IN  47405-6801     812-855-5782

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