In this report the research into the development of an attract- and kill strategy for sciarid flies (Sciaridae) and shore flies (Ephydridae) is described. First it has been evaluated which substrate compositions were the most and least attractive to sciarid fly females. Subsequently, an attractive substrate has been developed, which in combination with a yellow sticky trap could attract twice as many sciarid flies in a commercial greenhouse as a yellow sticky trap alone, and in cages could reduce the number of sciarid flies that developed in the growth substrate of viola plants to 50%. Moreover, the predatory beetle Dalotia (previously Atheta) coriaria was also attracted to this substrate. Shore flies did not react to odours of substrate or algae. However, in a greenhouse compartment a spontaneous contamination of shore flies with an entomopathogenic fungus was discovered. The effectiveness of this Beauveria bassiana isolate against shore flies has been compared with commercial entomopathogenic fungi, and has been subsequently used for the development of an attract- and kill method. Experiments have shown that shore flies can transfer this deadly fungus from containers with algae to which the fungus has been added, to other algae spots where shore flies develop.