Sciarid flies (Re: CP digest 474)

Juerg Steiger (
Thu, 21 Sep 1995 19:22:38 -0500

Hi all (John Walker, John and others)

>Perhaps it may be insects. My ping catches alot of tiny black winged (I
>think) bugs. These bugs jump away when I try to smash them. From previous
>discussions I think they may be thrips?
>Anyhow, I will try some weak diazanon a couple of times and see if it makes
>any difference. Thanks for the advice!

Are these tiny things really bugs and not flies? At natural habitats Pings
frequently catch little black 'sciarid flies' of 2mm lenght (Bradysia
paupera, Licoriella sp. and other species). The larvae of these miniflies
feed in wet substrate from tender plant roots. In artificial monocultures
of Pings and other CP sciarid fly larvae are likely to feed from the
tender roots of the cultivated plants. This is one of the most frequent
causes why Ping seedlings and young plants suddenly perish.

Diazinon in normal dilution kills the larvae and some of the pupae, but it
also kills or at least damages most Pings if the solution gets on the
upper (glandular) surface of the leaves. More diluted solution (e.g.1/4)
does less harm to the Pings but usually does not not kill all larvae.

To avoid the disadvantages of diazinon I've tried this year a biological
method: Bacillum thuringiensis ssp. israelensis kills selectively larvae of
sciarid flies (and also of mosquitoes, Culex pipiens and others). It enters
the digestive tract of the larvae and destroys it. Solutions of Bacillum
thuringiensis are commercially available. I sprayed it in the usual
dilution all over the leaves and the substrate. The portion reaching the
substrate kills the sciarid larvae and the portion reaching the leaves
enjoys the plants' appetite: the bacterial proteins and the nutriciant
fluid obviously activate the digestive glands and the plants grow really
vigorous. I applied Bacill. thuring. a first time in may 95 and again 10
days later. Then I repeated the treatment each 5-6 weeks. Sciarid flies
have practically disappeared, the adult plants grow as never before and the
loss of seedlings and young plants was practically zero. As I have mainly
Pings I can not report about experiences with Drosera or other CP. For
growers with sciarid fly problems the bacterial method is an ecological and
very recommendable alternative to diazinon, particularly also for outdoor
cultivations. In Switzerland Bacill. thuring. ssp. israel. is available
under the label 'Teknar' at Andermatt Biocontrol Ltd., Unterdorf, CH-6146
Grossdietwil. Phone +41 (0)63 592 840; Fax: +41 (0)63 592 123. 100 ml
(=20 l spray solution) cost 18 Swiss francs = 14 US$.

Comments of someone else who tried it? Juerg

Dr. Juerg Steiger, Institut fuer Aus-, Weiter- und Fortbildung IAWF
University of Bern, Inselspital 37a, CH-3010 Bern, Switzerland
Office: +41 (0)31 632 98 87, Home: +41 (0)31 972 19 79
Fax: +41 (0)31 632 98 71, e-mail: