Kouichi Inoue

The rate of population increase of the citrus red mite, Panonychus citri (McG.), at various seasons.

In this paper, we deal with the rate of population increase of the citrus red mite on the citrus young trees in the outdoors at various seasons (1967-1969).The purpose was to study the method for determination of the time necessary to spray acaricide from the present population of mites and their increase rate.1) The increase rate of the citrus red mite population was largest in summer during periods with average 28°C and without rainfall. In these. condition, the population increased about 8.5 times in ten days. It was 2.6 to 7.0 times in summer-fall, 2.3 to 3.4 times in spring, 1.2 to 1.8 times in fall and 0.8 to 1.9 times in the rainy season.2) In the rainy season, much rainfall strongly affected to the rate of population increase during periods of larva, nymph and adult.3) The test on the relation between population density of the citrus red mite and its rate of increase in fall showed that, the rate of increase in mite population decreased severely at the densities of more than 80 eggs leaf at start.4) The rate of population increase in ten days at summer and summer-fall seasons, on the leaf heavily infested by mite, decreased to about one sixth and one third of the uninfested ones.