Changes in the Distribution Pattern, Sex Ratio and Age-Class Structure during Population Growth of the Gitrus Red Mite, Panonychus citri (MCGREGOR)

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Changes in the distribution pattern, sex radio and age-class structure of the citrus red mite, Panonychus citri (MCGREGOR), during the population growth were investigated on citrus saplings planted in the greenhouse and in the field.Distribution pattern of individuals of all stages of mites on a sapling was contagious but the adult females distributed more randomly than the other staegs. The sex ratio, ♀/♀+♂, was about 60-70% in the greenhouse and 70-80% in the field. The age-class structure fluctuated widely at the initial stage of the experiments and gradually stabilized. When the age-class structure stabilized, the ratio of eggs in the population was about 54% and 72% in the greenhouse and the field, respectively. This difference was considered to be due to high mortality in the early stage of the development in the field. Expected changes in the age-class structure with time were estimated by a LESLIE matrix using data on mortality and fertility obtained under laboratory conditions where temperature was kept constant. The expected fluctuation patterns of the age-class structure (damped oscillation and shorter cycle under higher temperature condition) were similar to the observed experimental results. Changes in theoretical stable age-class structures due to changes in the mortality and fertility schedule were investigated to evaluate the effect of mortality and fertility on the population dynamics of the mite.
1980-11-25