Effect of Fungicides on Germination and Growth of Fungi Associated with Esca Disease of Grapevine in Vitro

Esca of grapevine is a serious and injurious disease in grape-growing all over the world، for which no effective control exists. The presented research، in two separate experiments، thirteen fungicides (benomyl، thiophanate-methyl thiram، mancozeb، fosetyl-Al، metalaxyl mancozeb، caboxin thiram، ortiva، topas، penconazole، tebuconazole، propiconazole، sodium arsenate، agri-fos) were evaluated for their in vitro effects on conidial germination and mycelia growth of Phaeoacremonium iranianum (Phi)، Phaeomoniella chlamydospora (Pch) and Fomoitiporia mediterranea (Fmed)، the most causal agents of esca diseases of grapevine in north Khorassan province. Those experiments were tested in a completely randomized design with factorial arrangement and three replications. For each fungicides eight concentrations (0،0. 1،0. 2،1،2،3،10،100) were assessed. The different fungicides were added to MEA in order to achieve the experimental concentrations. Mycelial plugs of each pathogen were transferred to the center of the fungicide amended plates. After 10 days، the daily growth rate relative to the unamended control was estimated. The results showed that sodium arsenate was found to be the most effective fungicide in inhibiting the colony growth of three associated fungi of esca followed by carboxin thiram and benomyl against Fmed and two other pathogens respectively. Meanwhile Agri-fos and ortiva were less effective. Additionally، Conidial suspensions (5x105 conidia ml-1) of both pathogens Pch and Phi were exposed to 3ppm concentration of the different fungicides. After 24 hours، the percent conidia germination relative to the control treatment was assessed. Sodium arsenate (87. 51%) and thiophanate-methyle thiram (85. 93%) were highly effective on suppression spore germination. Meanwhile Agri-fos (20. 55%) showed less performance in reducing spore germination of two pathogens.