What are the problems with traps?
Traps use more materials than targets and consequently they are more expensive. So for controlling tsetse you should use targets rather than traps. If you want to carry out surveys however, you will have to use a trap.
The main problem with traps is that to be effective, they must be maintained properly.
First, it has to be assembled correctly, quite small errors can greatly reduce the efficiency of a trap. For instance, a small gap between the top cage and the netting cone of an Epsilon trap will allow flies to escape.
Second, traps will get damaged with use. They get blown over, the cloth gets ripped, the colour of the cloth fades. So they need a lot of care to be effective. Ideally they need to be visited daily, and every 2-3 days at very least, so that the trap cage can be emptied and the flies counted, the supporting ropes tightened, and any minor damage can be repaired. Visiting traps frequently also deters theft.
Resist the temptation of erecting a trap and then visiting it a month later, thinking that you will have a month's worth of flies. It will almost be certainly be missing or damaged when you return and you won't know whether the absence of any flies was because there is none in the area or that they all escaped.