The role of resting spores in the survival of the mite-pathogenic fungus Neozygites floridana from Mononychellus tanajoa during dry periods in Brazil.

Abstract

Survival of pathogens during long periods of unfavorable conditions can be critical to their ecology and to their use in biological control. In northeastern Brazil, the mite pathogen Neozygites floridana must survive hot and dry conditions between wet seasons when it infects the cassava green mite Mononychellus tanajoa. We report on large numbers of mite cadavers bearing resting spores towards the end of epizootics in mid-1995. High within-leaf variability indicated that local factors may be important in determining resting spore formation. These spores remain in the host cadaver on a leaf until the cadaver breaks up, whereupon the spores fall freely to the soil, there to remain dormant. Laboratory simulation of field conditions led to ca. 25% of mycosed individuals bearing resting spores. Mummies (without resting spores) kept in hot and dry conditions showed little or no viability within 2 months, implying no role for survival over extended dry periods. It is proposed that resting spores form the principal means by which this pathogen survives the dry season in the study area. This has implications for its introduction to new areas in classical biological control.