that would be needed to describe the potential exposures beyond generalizations. If a concerted effort to develop the mycoherbicides is embarked on, Figure 2-1 could be used as a guide to identify where the data gaps are and the types of information that are needed to characterize potential exposures.
Classical or Bioherbicide Approach
The registered mycoherbicides discussed earlier (Table 2-2) were all developed from pathogens indigenous to the regions where they were proposed to be used. Unless a decision is made to develop only strains indigenous to the relevant crop-producing areas, a mycoherbicide based on a nonindigenous strain may require more comprehensive testing to assess the risk to nontarget plant species than would a mycoherbicide based on indigenous strains. The higher level of testing would be comparable with the current testing requirement for the release of a classical weed-biocontrol agent. Such extensive testing may not be required in regions where the mycoherbicide pathogen is indigenous and has never been found to pose a risk to nontarget plant species. It is presumed that the proposed mycoherbicide strains would come from the population of fungi found in the geographic area where the target crop is being grown. If the mycoherbicide were released in areas where the pathogen is not native, estimating the potential for disease in nontarget crops caused by the released mycoherbicide strain or strains descended from it would be far more complicated.