[Odonata-l] nymph dying in pond

[Fred SaintOurs]

Some pesticides work by disrupting the chemical processes during eclosure, preventing larvae from fully developing. Is there a chance that pesticides from a nearby lawn, garden, or water body are getting in the pond water?

FS
Frederick SaintOurs
http://efg.cs.umb.edu/keys/html/index.html
  ----- Original Message ----- 
  From: Kathy &/or Dave Biggs 
  To: Odonata discussion group 
  Sent: Monday, May 21, 2007 4:43 PM
  Subject: [Odonata-l] nymph dying in pond


  I'm hoping someone can help this woman who is finding dead nymph in her pond.
  I'll paste in her messages:


    Hello Kathy,

    As I re-read your book "Common Dragonflies of California", this time I noticed your website on the back cover.

    I have had a small pond for about 7 years now, and have enjoyed gradually discovering the lifecycle of the dragonflies that have come to my pond.  The very disheartening problem I am seeing this year, more than ever before, is that most of the nymphs are dying, just when it looks like they are mature enough to climb up on a stem and transform themselves into dragonflies.

    So far this year I have found only 2 exoskeletons, while this morning alone, I fished out 3 dead little bodies floating in the water.  In an attempt to figure out why, I have tried the following:

    I have 7 pots in the pond, but only two of them have stems that stick out of the water (papyrus and water iris).  Is it possible that the nymphs cannot find an appropriate stem when they are ready to climb out?  I added 2 rough, weathered sticks into each of the other 5 pots.  So far, I have found nothing to indicate that any nymphs have climbed on the sticks.

    I use San Jose city water to "top off" the pond each morning.  Thinking that perhaps the chemicals in the water were killing the nymphs, for one week I used Aquarium AmQuel, a detoxifier that says it removes ammonia, chloramines, toxic pheromones and chlorine, each morning as I topped off the pond.  The nymphs continued dying on a daily basis.

    To clear cloudy water, I use Acurel E.  For the many years that I kept aquarium fish, I used the companion product, Acurel F, and swore by it, for keeping aquaiurm water clear and healthy.

    Have you encountered this problem?  Any ideas you have will be much appreciated!

    Sincerely,
    Gloria McClain 

    Hi Kathy, 

    Thank you for your very quick reply. Unfortunately, there is meat inside, and on their back it looks like rudimentary wings have started to come out. But they are quite dead --- I have tried putting them on a stem in case they might continue evolving, or crawl slowly back into the water. They don't. Their underside has turned kind of a pink color, and depending on how dead they are, their odor is left on my hands even though I did not squash them. The dogs find them to be a very tasty tidbit, if I leave them where the dogs can sniff them out and reach them. But they are not interested in the empty exoskeleton.

    My pond is in a very protected area of my back yard, and stays warmer than a more open area would. This spring I've seen orange dragonflies (sorry I can't be more accurate about which orange ones). Just a couple of days ago I watched one deposit eggs while hovering over the water. Its the first time I have seen that. All the others I have watched (in previous years) have landed on a stalk, just close enough to the surface of the water to stick their tail beneath the surface and it looked like they were sticking their eggs on the stalk, below the surface.

    Gloria
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