Test species selection
It is important to choose an appropriate range of species for use in host range testing experiments. Some of the most important issues are discussed below.
A general problem that is gradually becoming much better understood is the existence of previously unrecognised biotypes. Either the weed, the agent or the natural enemy may actually consist of several distinct populations that vary biologically but are lumped under a single taxonomic name. For example, a parasitoid may only attack some of the populations of a host. Conversely, a parasitoid may exist as several distinct biotypes, each of which shows behavioural or physiological adaptation to different hosts.
Because of the far-reaching consequences of biotype specificity and effectiveness, host range testing should be done with the exact geographic population of parasitoid that will be released. This important issue needs to also underline all the considerations listed below.
Weed biological control agents