Sporulation kinetics and conidial viability of Nomuraea rileyi (Farlow) soon on cadavers of the velvetbean caterpillar, Anticarsia gemmatalis Hubner (Lep.: Noctuidae) in the field

摘要

The entomopathogenic fungus Nomuraea rileyi (Farlow) Samson produces epizootics on populations of the velvetbean caterpillar, Anticarsia gemmatalis Hubner, resulting in its natural control. However, sometimes this phenomenon does not occur soon enough to prevent pest population outbreaks and damage to the crop. Observations of N. rileyi conidial production on the surface of A. gemmatalis cadavers in the field showed that high relative humidity and precipitation determine the sporulation dynamics. Infact, initiation of sporulation is delayed and conidia production is reduced when A. gemmatalis cadavers infected with N. rileyi are exposed to water stress (relative humidity 25-30 percent) in the laboratory. Field observations also demonstrated that N. rileyi conidial viability remain high (>75 percent germination) until 10 days on A. gemmatalis cadaver surface, acting as an inoculum source for this period.