PATHOGENICITY STUDIES OF A FUNGUS ASSOCIATED WITH Mononychellus tanajoa (Bondar), MITE PLAGUE OF YUCCA (Manihot
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Abstract
In the cassava crop (Manihot esculenta Crantz), tetranychid mites cause considerable losses. Fungal epizootics that affect Mononychellustanajoa (Bondar) populations have been detected under field conditions. Healthy mites were infected under controlled conditions in the laboratory. Daily observations were made with a dissecting microscope, in order to identify disease symptoms progression. Mites were mounted on a slide and examined with a phase-contrast microscope in order to confirm the presence of a fungal pathogen and to determine its identity. Reinfection occurred when a healthy and infected mite were placed together at 70% R.H. and 209-30°C. Symptoms of infection progressed from changes in body color, swelling, and sluggish movements, to death and mummification. Invasion by secondary pathogens was common. Each symptom was related to a developmental stage of the fungus, which was identified as a species of the genus Neozygites. Neozygites sp. is pathogenic to all mobile stages of M. tanajoa. Conidiogenesis was inhibited at relative humidities below 65%; however, the formation of adhesive conidia responsible for the propagation of the infection occurred only below 65% H.R. No evidence was found for pathogenicity of this fungus to phytoseiid mites
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