Importance of ambient saturation deficits in an epizootic of the fungus Neozygites floridana in cassava green mites (Mononychellus tanajoa) |
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Authors: | Elliot Sam L De Moraes Gilberto J Mumford John D |
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Institution: | (1) Imperial College at Silwood Park, NERC Centre for Population Biology, Ascot, SL5 7PY, United Kingdom;(2) Departamento de Entomologia, Fitopatologia e Zoologia Agrícola, Escola Superior de Agricultura “Luiz de Queiroz”, ESALQ/USP, 13418-900 Piracicaba, Brazil;(3) Imperial College at Silwood Park, Environmental Science and Technology, SL5 7PY Ascot, United Kingdom |
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Abstract: | The mite-pathogenic fungus Neozygites floridana Fisher (Entomophthorales: Neozygitaceae) is considered to have potential for the biological control of the cassava green
mite, Mononychellus tanajoa (Bondar). However, its activity is sporadic and laboratory data suggest a strong dependence on night-time saturation deficits
for transmission. We report on an epizootic of this fungus in a mite population in northeastern Brazil. During the epizootic,
host populations appeared to be limited by a combination of the pathogen and a predatory mite Neoseiulus idaeus (Acari: Phytoseiidae). When temperatures increased, the epizootic finished and the host population began to grow. Abiotic
conditions could not explain the variation in host mortality following pickup of infective propagules in this epizootic. However,
night-time saturation did help to explain the variation in transmission from infective cadavers to newly killed hosts. This
supports laboratory observations that horizontal transmission between hosts is determined mainly by saturation deficits, while
the process of infection is little affected by abiotic conditions. A further field observation was the near-absence of resting
spores in dead mites (ca. 0.1% of cadavers), suggesting that the pathogen population was unsuccessful in producing inoculum
to infect future M. tanajoa populations. The implications are that this pathogen will only be effective as a biological control agent in periods of high
relative humidity, and establishment in new areas may be limited by resting spore formation.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | Biological control Cassava green mite Climate Epizootiology Fungal pathogen Neozygites floridana Predatory mites |
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