Why would you want to manage pests, not only kill?
Good question.
Well the first thing is that the old strategy of control was done with control problems from.
Kill the parasite does not always work in the long run. Pests have developed resistance to chemicals and you can only kill the robber, with clear strategies. Then you end up with errors and not super predators. DDT also great that many farmers and mosquito control people groaned when he made the market at this point pretty much useless in controlling mosquitoes. Already there was a lot of resistance in insect populations and other mosquito was determined and the worse.
Kill a pest at once can cause the growth of other parasites, who was present, but no problem. For example, we consider the case of hemlock eriophyid mite and two spotted spider mite. So you want to kill the eriophyid Sevin, and choose how he kills the mites really a great job. Sevin has no effect on two-spotted mites Mite in the least, but it is terrible on this predatory mite. Now you must not have mites, but Eriophid a population explosion of the Two-Spotted Mite. So you have only exchanged one problem for another, and gave money for the privilege.