ミカン園の総合的害虫管理 (IPM) についての実験的研究  [in Japanese] Experimental Study on the Integrated Pest Management (IPM) in Citrus Grove  [in Japanese]

An experimental study on the integrated pest management (IPM) was made in citrus groves during seven years (1970-1977), following the data of four years by a preliminary study (Nakao, Nohara and Ono, 1972, 1974). As shown in Table 1, the method was as follows : (1) the insecticide selected against scale insects was low toxic to the natural enemies and sprayed in alternate lines of trees ; (2) against mites and aphids, any pesticide was not used but the water under 14 atmospheric pressure was sprayed ; (3) pruning was made in order to lighten the condition of citrus grove, because the scale insects like dark habitat. The result is summarized below. The control was effective as expected against arrowhead scale (Unaspis yanonensis KUWANA), the most serious pest, as shown by the data in No.2 grove (under IPM) during seven years. It is also so in No.2 grove against citrus red mite (Panonychus citri MCGREGOR), another serious pest, whose number was less than the threshold giving rise to damage to production. The number of species in predacious insects is almost the same between No.1 grove (customarily sprayed) and No.2 grove (under IPM) but the number of individuals was larger in No.2 grove where the power of natural enemies was apparently stronger. In No.3 grove (under IMP), no spraying was made during several years before the start of our study when both of the pest and predacious natural enemies were high in population, but the number of pests became small constantly three years after the start of IPM. The number of predacious natural enemies became smaller too but was larger than in No.2 grove, suggesting that the effect of control becomes more constant when IPM will continue for a long time. Between No.3 grove and the windbreak hedge consisting of a row of trees whose Japanese name is Isunoki (Distylium racemosum SIEB. et ZUCC.) (which surround No.3 grove), the fauna of the predacious natural enemies is not different but common. This shows clearly that the above Isunoki trees are important for shelter and source of the natural enemies.