Abstract: There is a close relationship between the amount of content of P and K in soil and the incidence of the disease. When the content of P in soil is high, the incidence of the disease would be slight. When the content of K in soil is high the incidence of the disease would be serious. Index of invasion is in a negative correlation with P/K based upon the results, ³²P and ⁸⁶Rb were used as radioisotope tracer in uptake by diseased twigs and leaves of Paulownia. Results indicated that the species which is resistant to the disease absorbed more K and less P than the species which is susceptible.

Key words: Witche's broom, Paulownia, Isotope, Tracer