A STUDY ON POPULATION DYNAMICS AND CONTROL OF THE CITRUS ARROW-HEAD SCALE UNASPIS YANONENSIS(KUWANA)

In Hua Ning area,the citrus arrow-head scale has two generations a year.It overwinters mainly as inmature female adults.During the second 10 days of Februay when daily mean temperature reaches to around 17℃,the overwintering females begin to oviposit.There appear 4 egglaying peaks respectively during the second 10 days of March,the last 10 days of April,the last 10 days of June and the second 10 days of Au-gust,with the first peak being the most prominent.Two Aphelinid parasites,namely Aphytis yanonensis Debachi et Rosen and Physcus fulrus Compere et Annecke have been observed parasitizing the female adults.Omethate,Quinolphus,Supracide and Buprofezin have been tested for control of the peak period nymphs in the field.These insecticides all show promising results with omethate appearing the best.The period from the last 10 days of March to the end of April has been accepted as the optimum time for control.