QUESTION 4: Gypsy Moth Spraying
I wish I could give you more information about the other organisms
that may be effected by the Bt spraying. I have been told that the
spray will effect other moth and butterfly larvae not just gypsy moths.
So any larvae present at the time of the spraying are at risk. Because
of our unpredictable weather, I can't tell you for sure what will be
hatching out at that time. Our warm winter and cold spring has sped up
the life cycles of some insects and slowed down others. For more
information about the effects of Bt spraying I would contact the USDA.
-- Mary H of Newburg, WI
Any caterpillars that are actively feeding inside a spray block could
be affected. Btk does not impact adult butterflies and moths (or their
eggs and pupae). The Btk spray only stays active for 3-5 days -- it
degrades rapidly in sunlight. Most spray blocks are 500 acres or less,
thus areas are rapidly recolonized by butterflies and moths, usually
within a year(for larger spray block it may be 2 years). Since you
only have an acre, you could protect special areas (e.g. butterfly
gardens, or other special food plants) on the spray day with a tarp.
(Gypsy moth is mainly on oaks, other forest trees, and a few shrubs,
so covering ground plants should not negate the benefits of the spray).
Courtesy of Dennis Haugen of USDA Forest Service, St. Paul, MN
– Barbara S of Minneapolis, MN
From what I've been told, the Bt will kill all other Lepidoptera in the
area and there are many in a wooded area in spring.
I'm still doing some research on the Gypsy moth larva. Someone gave me
eggs last Aug., because they knew I wanted to see what the caterpillar
and adult looked like, and wanted to photograph them, etc. Of course,
I would never release them into the wild. When they hatched this year
on 4/27/02, there were hundreds. I froze all but 15-20. Since none of
their food plants were leafed out, I fed them roses from my atrium.
They never seemed to eat any of the leaves. When I found birch leafing
out a couple of weeks ago, I switched their food plant. They still
don't appear to eat the leaves. They are very, very tiny. In other
words, they haven't grown much. Only 3 have survived, so far. They are
the most difficult caterpillar I have ever tried to rear. I'm going to
be asking some questions of people who are supposed to be much more
knowledgeable than me about this subject.
In a comparison, I had eggs of the Speckled Green Fruitworm (Orthosia
hibisci) hatch on the same day, 4/27/02. Those caterpillars have eaten
their food plant, grown and are now pupating. I'm beginning to think
Gypsy Moths don't eat leaves, more likely they eat the bark, which
weakens the tree causing leaves to drop. My friend, Alice Gilles, in
Cascade, WI has observed them in her yard over the past two years.
Those are her observations, as well.
I'm thinking the Bt probably does more harm to other Lepidoptera than
the Gypsy Moths. If the caterpillars eat the bark, they are protected
somewhat from the spray, whereas the leaf-eating caterpillars are not.
Maybe that's why the spray doesn't appear to be doing any good in many areas.
These are just my observations and comments at this time. I may learn
more as time goes by. There are times when I question how much the "experts"
really know about the Gypsy Moth.
-- Janice S of Bailey’s Harbor, WI
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