Ecological Burns, Gypsy Moth Control

[David Cappaert]

I conduct an ongoing census of butterflies in the city of Ann Arbor, MI,
information that assists in our efforts to preserve diversity in natural
areas.  I have 2 questions that others might have some experience with
....

Impact of Ecological Burns
A key management strategy to reduce exotic invasive plants is prescribed
burning.  Over the last 3 years, burns have been quite effective in
eliminating buckthorn, honeysuckle, and other invasives, allowing the
reappearance of native herbs.  What are the likely impacts on
butterflies (and other inverts)?  Interestingly, census data do not
indicate radical changes in butterfly populations or species composition
in areas that have been intensively burned.  But there is so much normal
variance that changes might be hard to detect.  Furthermore, we haven't
been able to conduct truly controlled experiments to compare burned and
unburned areas.  Are there any studies on this topic?  Are there
particular species that might be expected to be especially vulnerable?

Gypsy Moth Control
Some areas of Ann Arbor have been hard hit by gypsy moths this year.
The evidence as I understand it is that diseases will contain the
outbreak in the next year or two, and that control may not be
necessary.  However, people tend to panic when they hear the rain of
frass and see winter-bare trees in July.  So B.t. application is likely
next year.  I would like to be able to assess the potential impact on
our butterflies.  Is there good information on this out there?

In particular, I would like to be able to say what butterflies are
vulnerable to B.t. at a particular date (B.t. will kill them if they are
actively feeding caterpillars at the time of application).  I know when
adults are present in our parks, so I could back-calculate to determine
when each species was probably abundant in the caterpillar stage.  But
this requires knowing the time between pupation and emergence for each
of 60-some species.  Does anyone know of a good way to project this
information?  Has it been done elsewhere?

Yhanks for any ideas on the above questions.  I would also be happy to
hear from anyone working on local surveys similiar to Ann Arbor's.

        -- David Cappaert (cappaert at umich.edu)
           Natural Area Preservation
           Ann Arbor Parks and Recreation
           1831 Traver Rd
           Ann Arbor, MI 48105