EFFECT OF COPPER SPRAYS ON THE POPULATION DYNAMICS OF THE CITRUS RUST MITE, PHYLLOCOPTRUTA OLEIVORA (ACARI: ERIOPHYIDAE) AND ITS FUNGAL PATHOGEN, HIRSUTELLA THOMPSONII

MCCOY, CLAYTON W.

Abstract


Populations of citrus rust mite (CRM), Phyllocoptruta oleivora (Ashmead), and its fungal pathogen, Hirsutella thompsonii Fisher, were monitored weekly for 2 years on leaves of Marsh grapefruit trees sprayed at specified time intervals with a formulation of copper hydroxide containing 50% metallic copper. Seasonal fluctuations in CRM population density were similar from year to year but differed between treatments. From early May to mid-July, mite population densities were always lower on copper-treated leaves compared to the untreated controls. According to laboratory studies, the lower CRM population density in copper treatments was affected by reduced fecundity rather than increased adult mortality or reduced egg eclosion. Epizootics of H. thompsonii occurred in the unsprayed control in July both years. The incidence of fungal pathogen in mite populations was density-dependent and was affected by the time of copper treatment. Copper sprays applied before, during or after mite populations peaked in summer did not prevent but influenced the magnitude of the epizootic by causing a reduction in both CRM populations and the incidence of infected mites. Copper sprays did not incite a resurgence of the CRM populations in the fall.

Keywords


copper sprays; citrus rust mite; hirsutella entomopathogens

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283