Summary fungus gnat biocontrol

Jim Tokuhisa jtok at
Tue Sep 14 10:25:47 EST 1999


Original Query:
Have folks been successful using any biocontrol agents such as bacteria
(Bacillus thuringiensis var. israelensis), fingers (Homo sapien), mites
(Hypoaspis miles) or nematodes (Steinernema feltiae) to reduce fungus
gnat populations in  Arabidopsis forests?  I would be interested in
application/management schedules, other biocontrols, and comparisons of
effectiveness.  I will post a summary of responses.

We use a formulation of B.t. var isr. called Gnatrol. It works well. We
it every week as an overhead application according to the recommended
dosage. If an infestation gets overwhelming, we go to three times a
Yellow stickers help in monitoring and perhaps decreasing populations.

Luca Comai  <comai at>
I've found that Gnatrol works really well as long as plants are drenched

weekly.  I use a PlaySchool watering can (no kidding) and top drench.  I

use the kid's watering can because the droplet/stream size is smaller
those of "adult" watering cans.
I have been growing thousands of plants in one grow room continuously
sometime and have dealt with serious fungus gnat populations.  We have
had very
good results with Gnatrol (Bt) when applied weekly as a soil soak.  The
applications should be performed prior to the use of fertilizers
copper salts and repeated for at least 3-4 weeks(3 or 4 applications).
label lists several effective concentrations, but we feel the heavy and
grade applications work best.  Based on our experience the most
feature of the Gnatrol product is the age of the solution.  The
recommends using the stock within 'one season' of the date of
manufacture (I
figure about 4-6 months).  Anything much older yields poor results.
Abbott Laboratories for date of manufacture and distributors.  I have
the use of Gnatrol with many sticky traps to catch as many egg laying
adults as
possible.  If you have any questions please contact me through email.

George Aux <george.aux at>
Fungus gnats (Sciara spp., 'Trauermuecken', rouwvarenmuggen) in
greenhouse grown Arabidopsis have not been a problem anymore since I
started using Steinernema feltiae nematodes. I mix a suspension of the
nematodes through the potting soil before sowing. This prevents
infestation from other plants in the greenhouse. I apply another
treatment about 10 days after plant emergence. Normally this suffices.
It is more effective than the synthetic pyrethroids that I tried before
switching to biological control. I obtain them and other biocontrol
agents from Koppert Biological Systems in Berkel en Rodenrijs (NL),
either directly or through their distributor in Germany (Geereking,
Hamburg) [no affiliation with either company; there are probably other

Rik van Gorsel  <rvgorsel at>
I have had some success in controlling fungus gnats by using Steinernema

feltiae.  I apply 50 million in 300 litres with a watering can - to all
plants once every 3 - 4 weeks.  This is basically done as a preventative
measure for most of the plants - and I have trouble trying to find a
fungus gnat in our growth chambers these days.

Christine Larsen <CHRISTINE at>
Its not really biocontrol, but we
1. sterilise soil by autoclave (this seems to reduce the problem)
2. we also use electrocutors (uv light attractant to a high-voltage
3. sticky yellow cards

John G. Turner  <j.g.turner at>
Some years back when we had this problem at UCLA in our walk-in growth
chambers, we resorted to a nasty organophosphate insecticide,
I don't recall who made it (Shell?), but a greenhouse mgr would know
it.  It was very effective in dealing with the gnats (little black flies
larvae that devoured the roots of our young plants).  It came in an
can and we sprayed it over the flats of plants  (about 60s over a dozen
flats), then exited and sealed the chamber for 24h.  New growth (i.e.
leaves) took a hit, but we eliminated the problem with a single
I think.

Good Luck!  George Karlin-Neumann <karlin at>


Biocontrol summary:
Fungus gnat biology and control:
Insect growth regulator advert:
Nematode advertisement:
Gnatrol Advertisement:
Chemicals Advertisement

Jim Tokuhisa
Max Planck Institut für Chemische Ökologie
D-07745 Jena
Phone:  +49-3641-64-36-51
FAX:  +49-3641-64-36-50
E-mail:  tokuhisa at

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