Studies On The Biological Characteristics, Infection Cycle And The Control Of The Hyperparasite (Tuberculi Fraxinis)

The author had systemically studied and reported the hyperparasite (Tuberculia fraxinis) of ash rust pathogen. These studies may result in understanding the distributing, habitation, biological characteristics, life history cycle and its control and effects of T.fraxinis, and further some theory basis and methods of biocontrol are expected to obtain.1. Isolation and cultivate character of T. fraxinis Through improved and single entification the dark-purple spores are produced on the slide of PYA . And the spores can cont -inously breed and mass the swollen heap. The pale purple colony appeared after 3~5 days.The spores began to be produced after 7~8 days and the colour was red-brown or dark purple.2. Biological characteristics of T. fraxinis The hyperparasite (T. fraxinis) of Ash rust could produce many spores and grow best on the 4#(PYA) from different media. There were 6 kinds of carbon sources including sucrose and glucose, which were better for the mycelial growth and air-dried weight. The spores occurred on sucrose, fructose and mannitol media, among which glucose and mannitol were the best. Among nitrogen sources, KNO3 was the best for mycelial growth and air-dried weight. The spore formation was best on asparagines and peptone.The optimum temperature was 22C~25C (12 h displace). The optimum temperature and relative humidity for the spore germination are 24~28C, in drops of water., respectively, The death temperature for the conidia was 42C (10min). The optimum pH for the mycelial growth, the spore formation and the spore germination was 5.0-6.0. The fluorescence can promote the spore formation.3. Life history cycle of T. fraxinis The overwintering, dissemination and entry of the hyperparasite (T. fraxinis) of Ash rust pathogen (Aecidium fraxinibungeanae Diet) were reported. Under natural condition of Ya'an , the conidia of the hyperparasite overwintered on the parasited site. The percentage of the conidia germination was 18.70% after 250 days. The conidia were disseminated by airflow. The germ tube of the conidia penetrated through the ostioles of the spermogone and the aecium and did not penetrate directly. The shortest period for the entry was 10 h. The incubation period was 8~12 days at 16.7~20.6C.4. Control and effects of T.fraxinis The artificial hyperparasitic percentage was 80.60%when the spore suspension was sprayed, whereas the natural hyperparasitic percentage was 46.5%. The size of rust spot with the hyperparasites is 0.5~2.8 cm x 0.2~2.0 cm (average 1.2 cm x 0.8 cm), which is less than that of no hyperparasite( 0.8-3.8 cm x 0.6~2.3 cm, average 1.6 cm x 1.0 cm). All these results indicated that T. fraxinis could effectively lighten the serious degree of rust by minishing the size of rust spot and control rust disease.