Fungus gnats

Laurence Rueter
Mon, 21 Mar 2011 13:07:14 PDT
Hi-- Greetings from New Zealand. A few bulbs coming out here now, late  
in this exceptionally long and warm season here....

  I am very concerned about fungus gnats because I am raising around  
2000 seedlings of various Hosta. I have heard from friends in the US  
that there is a very effective predatory nematode available there I  
think it is Steinernema sp. Also in New Zealand we have someone here  
selling a predatory mite called Hypoaspis aculeifer. These and the Bti  
are especially interesting to me because I want to keep low my usage  
of poisonous insecticides. We do have the Steinema feltiae present in  
NZ, but no one seems to be growing it commercially. I have only used  
the Bti from mosquito dunks, and seem to have mderate success, as  
there has been very little attrition in my seedlings.
  I also let my mix dry out very on the surface between waterings, and  
water from the bottom of the pots. There are still fungus gnats  
present, though.
Another possible solution I have heard of is called NilNat. Which is  
some kind of small particle the gnat larvae will ingest when  
incorporated into the soil mix by watering. I ruptures their digestive  
One poisonous insecticide I have considered is called Dimilin, which  
is a growth regulator and though I have read of it's use on manure  
piles for fly maggots, it apparently can work on fungus gnat larvae,  
according to some growers of cycads here in New Zealand.
Hope this info can be encouraging for anyone faced with the  
opportunity that fungus gnats provide.... in teaching us about some of  
the life in our soil mix.
All the best, Larry Rueter, Nelson, New Zealand

More information about the pbs mailing list