involved in disease development under laboratory conditions, but no reliable data are available on the proposed mycoherbicide strains. The molecular mechanisms underlying the host-pathogen interactions are unknown, and the nature of disease progression and fungal spread after disease onset, which are critical determinants of mycoherbicide efficacy, are not documented.
• Are the proposed mycoherbicides host-plant-specific?
The proposed mycoherbicide strains can cause disease in their target plants, including those grown legally and those which occur naturally near the illicit crops. However, the few host-range studies conducted with nonrelated species were of little value because they only report that the mycoherbicide strains did not cause disease in some native plants and crop species and do not provide experimental details (or in some cases even the names of the plants). Furthermore, none of the available studies used a standard, systematic process to select the most relevant plants to test in host-range studies. For example, of about 200 species of Erythroxylum native to South America, only two were tested for susceptibility to the coca mycoherbicide. Thus, the data are insufficient to conclude that the proposed mycoherbicides would not pose a risk to other plants or crops.
• What quantities of mycoherbicides would be needed to eradicate illicit drug crops?
Workable mycoherbicide formulations, delivery methods, and application strategies need to be developed in partnership with an industrial producer before this question can be answered. The committee made estimates for a single application per hectare solely on the basis of published laboratory production methods, which may or may not be realistic. Its estimates indicate that tens to hundreds of kilograms of dry formulations per hectare or hundreds to thousands of liters of liquid-spray formulation (containing billions to trillions of spores) per hectare would be required for a single application of the mycoherbicides.
• How would the method of delivery affect the effectiveness of the mycoherbicides in eradicating the drug crops?
For all three mycoherbicides, on-ground application would be the most precise and uniform. However, it is not feasible, because the growers of illicit drug crops would be uncooperative and possibly hostile. Aerial application is probably the most practical approach, but it would need to be from altitudes greater than those normally used for agricultural applications.