Effects of Pulsed Magnetic Field on Growth and Infestation of Botryosphaeria dothidea Effect of PulsedMagnetic Field on the Growth, Physiolog ica l andBiochem ica l Character istics of P inus m asson iana Ca llus Effects of Pulsed Magnetic Field on the Biochemical and Physiological Characters and Ultrastructure of Pine Wood Nematode