Fungicides Screening For Chemical Control Of Four Fungal Diseases On Tree Peony Leaves

Peony not only has high ornamental vale, the root bark has a very high medicinal vale. In recent years, with the expansion of planting area of peony, peony disease is becoming more and more serious, severely reducing the ornamental and medicinal value. In addition to strengthen the cultivation and management, chemical control is the most effective measure of peony diseases. Benzimidazole, three triazole and strobilurin fungicides have broad antibacterial spectrum, reported significant inhibitory activity against a variety of pathogenic fungi, but there is still a lack of research on the prevention and treatment of fungal diseases of peony. We collected many peony disease specimens from peony planting garden in Luoyang, four kinds of pathogenic fungi of peony leaf diseases were separated, the pathogens are Cylindrocladium canadense, Pilidium concavum, Cladosporium paeoniae and Phyllosticta commonsii, respectively. Antibacterial activity of three kinds of fungicides on four kinds of pathogenic fungi were studied by using mycelium growth and spread plate method to screen better bacteriostasis effect fungicides which can provide a theoretical basis for chemical control of peony diseases.The results showed that:Cylindrocladium canadense: Benzimidazole fungicides had a strong antibacterial activity against mycelia growth of Cylindrocladium canadense, the EC50 of carbendazim and thiophanate-methyl were 0.2617 and 1.3379μg/m L; epoxiconazole also had a strong antibacterial activity against the pathogen, EC50 was 0.6921μg/m L; morphology toxicology research results showed that chemical treatment can increase the branch number and shorten the branch spacing of the tip mycelium, thereby inhibiting the mycelial growth.Pilidium concavum: Triazole fungicides had a strong antibacterial activity against mycelia growth of Pilidium concavum, the EC50 of epoxiconazole, difenoconazole, tebuconazole and propiconazole were between 0.0200~0.0966μg/m L; strobilurin fungicides also had a strong antibacterial activity against the pathogen, the EC50 of azoxystrobin and kresoxim-methyl were 1.0286 and 1.8410 μg/m L; tebuconazole had a very strong inhibition on conidia germination and germ tube elongation, spores couldn’t germinate when the concentration is 0.1 μg/m L; azoxystrobin had a stronger inhibition on sporulation when the concentration is at 1.0286 μg/m L; when the concentration of carbendazim is at 12.1668 μg/m L, sporulation structure couldn’t be formed.Cladosporium paeoniae: Azoxystrobin, tebuconazole and carbendazim all had inhibition on conidia germination of Cladosporium paeoniae, the EC50 were 0.0519, 0.0756, 0.2132 μg/m L, respectively; these fungicides also has strong inhibitory effect on germ tube elongation, when the concentration is 1 μg/m L, the inhibition rate is more than 80%; azoxystrobin and tebuconazole had a strong inhibitory effect on sporulation, when the concentration is 0.01 μg/m L, the inhibition rates were 74.24% and 97.87%, respectively, when the concentration is 0.05 μg/m L, inhibition rate reached 100%.Phyllosticta commonsii:Azoxystrobin, difenoconazole, kresoxim-methyl, carbendazim, epoxiconazole, tebuconazole and propiconazole all had strong antibacterial activity against mycelia growth of Phyllosticta commonsii, the EC50 were between 0.2470~4.0775 μg/m L, azoxystrobin had the best effect, followed by difenoconazole; the inhibition of azoxystrobin on spore germination and germ tube elongation was better than carbendazim and difenoconazole; carbendazim had a obvious teratogenic effects on germ tube; when difenoconazole at the concentration of EC50(0.4455 μg/m L), the inhibition of sporulation could be 100%.In summary, benzimidazole fungicides had better antibacterial effect on Cylindrocladium canadense, triazole and strobilurin fungicides had good antimicrobial effect on Pilidium concavum, azoxystrobin and tebuconazole had good inhibitory effect on spore germination and sporulation of Cladosporium paeoniae, azoxystrobin and difenoconazole had a stronger inhibitory effect on Phyllosticta commonsii. These conclusions can provide a theoretical basis for chemical control of peony leaf spot disease in production practice.