Diatomaceous earth and pest control

Sophie Parker <parker.sophie [at] saugov__sa__gov__au> writes

>Jutta Gopfrich <j.goepfrich [at] ledermuseum__de> writes
>
>>... Also we are looking for a source for
>>pheromone traps against certain beetles (Anthrenus).
>
>...
>We have experienced a problem with controlling anthrenus verbasci
>larvae in a museum entomology collection and I have done some
>investigation into suitable pest control methods.
>
>I had hoped that a dusting of diatomaceous earth (desiccant powder)
>under the entomology cabinets would control and kill travelling
>larvae. I contacted the entomologist of a company who imports
>Dryacide, a diatomaceous earth for the protection of grain in
>storage. However in his opinion, the anthrenus larvae had too many
>body hairs which would prevent the dust from scratching the wax
>cuticle on the larvae, thereby leading to their dehydration.

Any desiccant, such as a fine powder of silica gel or diatomaceous
earth is effect against any crawling insect or larva.  The underside
of an Anthrenus larva does not have the bristles and hairs
mentioned.  The desiccant therefore works well when a larva crawls
through it.  If the cabinets are raised on legs, a desiccant beneath
them would be a dubious approach.  These larvae work in the dark and
are not normally out in the open, as would be the case beneath the
cabinets if they are raised off the floor.  Normally such an
application is for cabinets which sit on an enclosed base some 4" or
so off the floor.  This dark, enclosed area does accumulate hair and
other protein-based debris which may act as a source of carpet
beetle problems.

As for the comment about leaving the drawers slightly "open" so the
pyrethrum "gas" can penetrate them, someone has misinformed you
about the abilities of a pyrethrum approach.  Any natural pyrethrum
or synthetic pyrethroid is a contact insecticide.  It will only kill
what it hits.  If a larva is feeding on the interior on an insect
carcass, it will not be exposed to the pyrethrum, and therefore will
not be killed.  Pyrethrum type insecticides have very little
residual effect.  Once the pyrethrum hydrolyzes, it's gone, and is
no longer effective.  It is definitely not a gas and will not
provide long term protection.

Freezing infested cases and then sealing them some way is a much
better long-term approach.  If the tiny, newly-hatched larvae cannot
penetrate the cases, there will be no more infestation.  Most
collections are infested when infested materials are introduced or
when someone working on a collection case leaves it open for a
period of time while they are working on the specimens.

Thomas A. Parker, PhD
President, Entomologist
Pest Control Services, Inc.
14 E. Stratford Avenue
Lansdowne, PA 19050
610-284-6249
Fax: 610-284-4494


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                  Conservation DistList Instance 18:39
                 Distributed: Friday, February 18, 2005
                       Message Id: cdl-18-39-007
                                  ***