Experiments on the Effects of Spray Program on the Damages Induced by the Pests and Diseases in Citrus Orchard

1. Experiment on a young Satsuma orange orchard in Isahaya City during

Abstract

Three kinds of spray programs named ordinary (9-10 times of spraying in one year), economic (5-8 times in one year) and minimum (3-5 times in one year) programs were carried out and the results were compared by the percentage of damaged fruits in each orchard. The experimental orchards were well managed and the density of insect pests and diseases was very low.
In 1966 and 1967, the differences in the ratio of damaged fruits among these three kinds of orchards were neglisible. In 1968, it was observed that the damaged fruits were most abundant at the orchard of minimum program, but the differences were not so important.
In conclusion, it seems that the minimum types of spray program (only three or four times of spraying in one year) may be adopted and the remarkable curtailment of expenditure may be possible in citrus orchards in which the damages by pests and diseases were scarcely observed.