Potential of the mite-pathogenic fungus Neozygites floridana (Entomophthorales : Neozygitaceae) for control of the cassava green mite Mononychellus tanajoa (Acari : Tetranychidae)

The cassava green mite, Mononychellus tanajoa (Bondar), is an exotic pest i n Africa and is the target of a classical biological control programme. Fie ld data from the Neotropics, where it is indigenous, are presented for the first time, charting the variation in abundance of M. tanajoa over several seasons. This was highly variable, with a characteristic trough mid-year an d a peak at the turn of the year. This pattern corresponded positively with rainfall levels, appearing to fit a phenology also characteristic of Afric an studies, where rainfall at the start of the wet season promotes a leaf f lush and so growth in M. tanajoa populations. Analyses implied some impact of leaf-inhabiting predatory mites (predominantly Neoseiulus idaeus Denmark & Muma) and a considerable impact of the fungal pathogen Neozygites florid ana Fisher on M. tanajoa populations. This pathogen was not observed in the host population for several (generally dry) periods implying survival outs ide the host, perhaps as resting spores. This is a particularly desirable c haracteristic of a biological control agent. It is therefore proposed that N. floridana might be of particular use in drier cassava-growing areas wher e rainfall at the outset of the wet season is not sufficiently intense to c ause heavy M. tanajoa mortality but may be sufficient to stimulate epizooti cs of the fungal pathogen, protecting the flush of new cassava growth.