SEASONAL AND HABITAT VARIABILITY IN THE FUNGAL PATHOGENS, NEOZYGITES CF FLORIDANA AND HIRSUTELLA-THOMPSONII, ASSOCIATED WITH CASSAVA MITES IN BENIN, WEST-AFRICA

A survey of the pathogenic fungi associated with mites on cassava in B enin, West Africa, revealed both geographical and seasonal variation i n the presence of Neozygites cf. floridana (Weiser and Muma) and Hirsu tella thompsonii Fisher on Mononychellus tanajoa (Bondar) and Oligonyc hus gossypii (Zacher). Few dead and infected mites were found during t he dry season, regardless of vegetation zone. In three of 30 surveyed sites, N. floridana was found infecting 1% of the dead M. tanajoa and 2% of the dead O. gossypii while H. thompsonii was observed infecting 20% of the dead M. tanajoa in a single site. The frequency of sites ha ving infected mites during the wet season was 3.5 times greater than t hat seen during the dry season. N. floridana infected 10% of the dead M. tanajoa and 19% of the dead O. gossypii on young leaves. Mites infe cted with N. floridana were found either in the coastal Southern Fores t Mosaic (SFM) or in the Northern Guinea Savanna vegetation zones. N. floridana was rare in the low mite densities associated with mature le aves H. thompsonii was found on 19% and 29% of the dead M. tanajoa on young and mature leaves respectively. All M. tanajoa infected with H. thompsonii on young leaves and mature leaves (75%) were found in the S FM. A single M. tanajoa was the only infected mite found in the Southe rn Guinea Savanna. Relatively few O. gossypii were infected with H. th ompsonii. N. floridana and H. thompsonii were found together in three sites, but never on the same host. Phytoseiids were never found infect ed with either pathogen. In a regression analysis, the number of dead mites was significantly estimated from the total number of mites for b oth species, regardless of leaf age. The numbers of dead M. tanajoa on mature leaves were also estimated from the proportion of infected wit h H. thompsonii. The numbers of infected mites on young leaves were es timated from their association with the SFM for M. tanajoa infected wi th H. thompsonii, and from total mites for O. gossypii infected with N . floridana. On mature leaves, infected mite numbers were estimated fr om the virulent or better adapted isolates of N. floridana to control M. tanajoa in Africa is discussed.