EFFECTS OF CLIMATE, NATURAL ENEMIES AND BIOCIDES ON 3 CITRUS MITES IN COASTAL NEW-SOUTH-WALES

Infestations of the citrus rust mite Phyllocoptruta oleivora (Ashmead), the brown citrus rust mite Tegolophus australis Keifer, and the citrus red mite Panonychus citri (McGregor), did not cause economic damage to orange (Citrus sinensis (L.) Osbeck) in two coastal New South Wales orchards during a three-year study. The seasonal abundance of the mites and their phytoseiid and coccinellid predators was defined using periodic regressions of transformed counts on time. Population peaks coincided with seasonal rises and falls in temperature and evaporation in late-summer/autumn and in spring/early-summer. Population troughs in late-spring/summer coincided with peaks in temperature and evaporation and reproductive dormancy in some of the coccinellids. Population troughs in winter generally coincided with troughs in evaporation and temperature, particularly in July when the average temperature was about 10-degrees-C. Partial correlation coefficients were used to determine the relationships between the predators and their prey. These were mostely nonsignificant at P = 0.05. Fort-nightly and daily fluctuations in wheather did not have any obvious effects on numbers of the mites. The effects of fungicides and pesticides applied during the study were not clear.