Except for a small number of cases in which biocontrol agents wereintroduced from the site of origin of a weed (classical biocontrol), therehave been few cases where a pathogen was virulent enough to perform costeffectively in the field as a mycoherbicide. Mycoherbicides are typicallyweed species specific, so compatibility with herbicides used to controlother weeds is often studied. There can be a synergy between mycoherbicidesand herbicides at the field level due to overlapping weed spectra (suchsynergies are not discussed in depth herein). Two approaches have been usedto ascertain whether there is synergy in controlling the target weed: (1)random screening with herbicides; (2) using herbicides as antimetabolites toinhibit specific pathways, enhancing virulence. Glyphosate is the mostcommon herbicide to synergize mycoherbicides, possibly due to its dualfunction as an inhibitor of biosynthesis of phenylpropanoid phytoalexins bysuppressing enolphosphate-shikimate phosphate synthase, or by suppressingcallose production (by inhibiting callose synthase) as well as inhibitingother calcium-dependent pathways due to the calcium-chelating properties ofglyphosate.