Host range of Exserohilum monoceras, a potential bioherbicide for the control of Echinochloa species.
Fifty-six plant species in 43 genera and 19 families, selected by using the centrifugal phylogenetic method, were screened against Exserohilum monoceras, a fungus collected in the Philippines on Echinochloa colona [E. colonum]. Trials were performed under both optimum greenhouse conditions with supplemental 24-h dew, and natural field conditions with no dew supplement. The compatibility of host-pathogen interactions was characterized by the time and level of sporulation observed on detached inoculated leaves. All Echinochloa species proved to be highly susceptible to this fungus under optimum greenhouse conditions as well as in the absence of a dew supplement. Rottboellia cochinchinensis was also highly susceptible to this pathogen, regardless of the presence of a supplemental dew period. Among the crops tested, only corn [maize] seedlings were slightly infected under supplemental 24-h dew conditions, but no disease symptoms were observed on corn in the absence of a dew supplement. Sorghum and sugarcane were hypersensitive to the pathogen under supplemental 24-h dew conditions, but no infection was detected in the absence of a dew supplement. All other species tested were immune to E. monoceras. Data on sporulation on detached leaves from inoculated plants indicated that E. monoceras was weakly compatible with corn. No disease symptoms and no conidia were detected on leaves of trap plants. In the field, E. monoceras produced no symptoms on corn plants.