We use Dimilin G (4% diflubenzuron) from Maag AG to fight the small
dipteran black flies (Trauermücken). It is a granular substance and
sprinkled onto the soil when the plants show the first few rosette
leaves.
In addition we use Neocid Total. It is a regular spray
containing permethrin (0.3%) and tetramethrin (0.15%). Spray it from
some distance onto plants or walls, shelfs etc. It is an all-purpose
killer (beetles, mites, ants, flies...) and kills the adult black flies
quite efficiently.
We also use Solbac from Biocontrol AG to fight black flies. It is based on Bacillus thuringiensis ssp. israelensis.
1.use 2.5 ml Solbac per 2-3 l of water (weak infection)
2.use 5.0 ml Solbac per 2-3 l of water (strong infection)
However, the best way to keep the black flies low is to move old plants, kept for harvesting seeds, to another place.
Against
thrips we found that Amblyseius cucumeris, a mite, seems to work quite
OK, at least if the thrips population is very small. They come in bags
that you put up between the racks. We get them also from Biocontrol AG