Dragon Fly Larvae

[jacovors]

Can anyone please tell me how many fry one Dragon Fly Larvae can eat in a day and how do I get rid of them?
One of my mud ponds are full of them and I everytime I look in the pond I can see one or two sucking out one of my fry.
What should I do?, hope there are more fry than larvae or should I introduce a bigger koi to eat them when the fry are big enough?
Jaco.
P.S. Will post pics this afternoon.

[Doug Ward]

Dimilin will get them, Jaco.

[jacovors]

Thanks Doug,
I checked the pond today and decided that there were too little fry left and I am afraid that the ones that are left will have scaring from the larvae.
I have more than enough from the same spawning in another mud pond to get the amount of good ones I want to keep.

The pics below are of some of my tosai from last year taken from the selling ponds that I think still have some chance of improving with age.
So there will be 11 koi in this pond plus the fry that might survive.
The bigger ones are about 10 inches and the smaller ones 6 to 7 inches.
Would make for a good experiment I think. I hope they enjoy those $%&^#@ LARVAE FOR DINNER TODAY.

http://www.jakoi.com/images/dsc02092.jpg

[dick benbow]

doug's suggestion is a good one. eveytime I drag our growth ponds I destroy all those caught in the nets. They are a feroshious preditor and you do need to deal with them ASAP.

[Werner]

It's indeed, disheartening, to see your livelyhood eaten by predators. A dragonfly larvae, depending on the species, can live up to four years in the larval stage.

Dimilin will take care of the problem, but will also kill most other aquatic life. Since Dragonfly larvae will consume up to 100 mosquito larvae per sitting, you may be trading up to a much worse problem.
Murphy’s Law of Pest Control: To treat a malaria outbreak in Borneo in the 1950s, the World Health Organization (WHO) decided to spray DDT to kill mosquitoes. The DDT also killed parasitic wasps which were controlling thatch-eating caterpillars. As a result, the thatched roofs of many homes fell down, and the DDT-poisoned insects were eaten by geckoes, which were in turn eaten by cats. The cats perished, which led to the multiplication of rats, and then outbreaks of sylvatic plague and typhus. To put an end to this destructive chain of events, WHO had to parachute 145,000 live cats into the area to control the rats.

It seems to me, with a little advance planning you can control the number of larvae, by using bug zappers around the pond to eliminate the parent and seining the existing ponds.
Just an Idea

[jacovors]

Thanks for the help guys,

To dose a mud pond is too big a risk for me because to estimate the gallons by size is too big a guess.
Do you think these Tosai I added to the pond would eat them?
I have seen people covering their ponds with 20% shade net to avoid the Dragon fly from laying it's eggs in the pond to begin with.

Thanks again
Jaco

[bekko]

I am unable to completely control them, but know that timing can be a BIG help. I try to drain the pond and dry things out to the extent possible before spawning (yeah, I know, who can predict spawning that well?). When the pond is refilled, it goes through reasonable predictable 3 week succession where there is a green water bloom, followed by a rotifer bloom, followed by a copepod/daphnia bloom. When the stars are properly aligned, the fry are ready to begin feeding just as the rotifer bloom gets going and the fry are large enough to take the larger zooplankton as those forms begin to dominate.

This schedule also does a lot to control dragon fly larvae. Most of the older dragon fly larvae are killed when the pond is drained. The dragon flies start laying eggs again as soon as the pond is filled. However, many of these eggs and/or the newly hatched dragon fly larvae become fodder for the koi fry as they grow. Some dragon fly larvae survive, but their numbers can be almost tolerable at times.

You have to experiment around to see how the plankton succession works in your region and at your temperatures. I know some guys for whom it works better to refill the pond only 10 days before the fry are stocked.

steve hopkins

[jacovors]

Thanks Steve,

I have three mud ponds next to each other and the middle one has the larvae, none of the other has.
Maybe as you suggested the other spawnings was done at the right time for the larvae has become food instead of the fry.

I will use this pond for the tobies when I cull.

Thanks again,
Jaco