Wild Ones   Wild Ones Archive 2002, Jun 05:  
  Ques#4: Gypsy Moth Spraying  

Wild Ones 2002 Archive

    QUESTION 4: Gypsy Moth Spraying

    Additional RESPONSES:


    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.

    Good luck,

    -- 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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